Afternoon all.

I've got a drum filter (like a big washing machine) for the pond.
It's driven by a 24v worm-drive gearbox DC motor thing.
Earlier this year the motor/drive packed up so I replaced it with a
slightly faster turning unit as the original one was way too slow and
wasted loads of water.

The following page has all the the spec. etc.
http://www.motionco.co.uk/motors-wor...r-c-54_73.html

OEM unit was the last one on the list GMW40W0634 which I replaced with
GMW40W0505 - Speed and torque on the new unit are perfect however the
initial start-up current (apparently) of the new unit overloads the 24v
2A supply PSU causing it to shut down and re-start and so the on-going
cycle continues.

Manufacture has advised this doesn't happen on the correct unit (slow)
drive.

If I rotate the drum to take up the slack in the gears etc, on start-up
the drum rotates without any issues so presumably the fraction of a
second on no-load when the slack is taken up allows things to work
perfectly.

The following vid. is far more useful to demonstrate the issue.
https://www.dropbox.com/sh/iy1g8ddw2...4Q7OxVWBa?dl=0
https://tinyurl.com/ybnzufb3

I want to stick with the new motor/gearbox because it's way more suited
to the drum cleaning operation and uses a fraction of the water to clean
a greater expanse of filter screen.
Could anyone suggest a suitable thermistor(?) to stick into the 24v
Motor feed that would limit the inrush current to not exceed the 2 Amp
cut-off of the PSU? (12 ohm ?)

Or... am I braking up the wrong tree or is there another solution?
I suppose a beefier 24v supply would do the trick?



Cheers All
Pete

On Friday, 8 September 2017 13:57:02 UTC+1, www.GymRatZ.co.uk wrote:
Afternoon all.

I've got a drum filter (like a big washing machine) for the pond.
It's driven by a 24v worm-drive gearbox DC motor thing.
Earlier this year the motor/drive packed up so I replaced it with a
slightly faster turning unit as the original one was way too slow and
wasted loads of water.

The following page has all the the spec. etc.
http://www.motionco.co.uk/motors-wor...r-c-54_73.html

OEM unit was the last one on the list GMW40W0634 which I replaced with
GMW40W0505 - Speed and torque on the new unit are perfect however the
initial start-up current (apparently) of the new unit overloads the 24v
2A supply PSU causing it to shut down and re-start and so the on-going
cycle continues.

Manufacture has advised this doesn't happen on the correct unit (slow)
drive.

If I rotate the drum to take up the slack in the gears etc, on start-up
the drum rotates without any issues so presumably the fraction of a
second on no-load when the slack is taken up allows things to work
perfectly.

The following vid. is far more useful to demonstrate the issue.
https://www.dropbox.com/sh/iy1g8ddw2...4Q7OxVWBa?dl=0
https://tinyurl.com/ybnzufb3

I want to stick with the new motor/gearbox because it's way more suited
to the drum cleaning operation and uses a fraction of the water to clean
a greater expanse of filter screen.
Could anyone suggest a suitable thermistor(?) to stick into the 24v
Motor feed that would limit the inrush current to not exceed the 2 Amp
cut-off of the PSU? (12 ohm ?)

Or... am I braking up the wrong tree or is there another solution?
I suppose a beefier 24v supply would do the trick?



Cheers All
Pete

I've not seen any PTCs of low enough resistance, maybe someone else has. Your psu is clearly not upto the motor's starting current. Probaly the simplest way to soft start it, if modding the psu isn't doable for you, would be with a light bulb & relay. The bulb is in series with the motor when power comes on, the relay shorts the bulb after 2 or 3 seconds using an RC delay to its coil.


NT

On 08/09/2017 14:03, wrote:
On Friday, 8 September 2017 13:57:02 UTC+1, www.GymRatZ.co.uk wrote:

I've not seen any PTCs of low enough resistance, maybe someone else has. Your psu is clearly not upto the motor's starting current. Probaly the simplest way to soft start it, if modding the psu isn't doable for you, would be with a light bulb & relay. The bulb is in series with the motor when power comes on, the relay shorts the bulb after 2 or 3 seconds using an RC delay to its coil.

I found the following:
http://www.mouser.co.uk/ProductDetai...8uws534N U%3d
or
https://tinyurl.com/y8p2upun

12 Ohm, 5 Amp NTC which I trust presume would limit start-up current to
2 Amps ?

A better supply. I'm not at all sure that a thermistor would be enough.
However you are in effect still using the same if not more current using
that method with the possibility under varying load of undesired strange
things going on.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"www.GymRatZ.co.uk" wrote in message
news
Afternoon all.

I've got a drum filter (like a big washing machine) for the pond.
It's driven by a 24v worm-drive gearbox DC motor thing.
Earlier this year the motor/drive packed up so I replaced it with a
slightly faster turning unit as the original one was way too slow and
wasted loads of water.

The following page has all the the spec. etc.
http://www.motionco.co.uk/motors-wor...r-c-54_73.html

OEM unit was the last one on the list GMW40W0634 which I replaced with
GMW40W0505 - Speed and torque on the new unit are perfect however the
initial start-up current (apparently) of the new unit overloads the 24v
2A supply PSU causing it to shut down and re-start and so the on-going
cycle continues.

Manufacture has advised this doesn't happen on the correct unit (slow)
drive.

If I rotate the drum to take up the slack in the gears etc, on start-up
the drum rotates without any issues so presumably the fraction of a
second on no-load when the slack is taken up allows things to work
perfectly.

The following vid. is far more useful to demonstrate the issue.
https://www.dropbox.com/sh/iy1g8ddw2...4Q7OxVWBa?dl=0
https://tinyurl.com/ybnzufb3

I want to stick with the new motor/gearbox because it's way more suited
to the drum cleaning operation and uses a fraction of the water to clean
a greater expanse of filter screen.
Could anyone suggest a suitable thermistor(?) to stick into the 24v
Motor feed that would limit the inrush current to not exceed the 2 Amp
cut-off of the PSU? (12 ohm ?)

Or... am I braking up the wrong tree or is there another solution?
I suppose a beefier 24v supply would do the trick?



Cheers All
Pete

"www.GymRatZ.co.uk" wrote in message
news
Afternoon all.

I've got a drum filter (like a big washing machine) for the pond.
It's driven by a 24v worm-drive gearbox DC motor thing.
Earlier this year the motor/drive packed up so I replaced it with a
slightly faster turning unit as the original one was way too slow and
wasted loads of water.

The following page has all the the spec. etc.
http://www.motionco.co.uk/motors-wor...r-c-54_73.html

OEM unit was the last one on the list GMW40W0634 which I replaced with
GMW40W0505 - Speed and torque on the new unit are perfect however the
initial start-up current (apparently) of the new unit overloads the 24v
2A supply PSU causing it to shut down and re-start and so the on-going
cycle continues.

Manufacture has advised this doesn't happen on the correct unit (slow)
drive.

If I rotate the drum to take up the slack in the gears etc, on start-up
the drum rotates without any issues so presumably the fraction of a
second on no-load when the slack is taken up allows things to work
perfectly.

The following vid. is far more useful to demonstrate the issue.
https://www.dropbox.com/sh/iy1g8ddw2...4Q7OxVWBa?dl=0
https://tinyurl.com/ybnzufb3

I want to stick with the new motor/gearbox because it's way more suited
to the drum cleaning operation and uses a fraction of the water to clean
a greater expanse of filter screen.
Could anyone suggest a suitable thermistor(?) to stick into the 24v
Motor feed that would limit the inrush current to not exceed the 2 Amp
cut-off of the PSU? (12 ohm ?)

Or... am I braking up the wrong tree or is there another solution?
I suppose a beefier 24v supply would do the trick?



Cheers All
Pete

Why does the controller in your video say 12VDC, not 24V? I can't make any
sense of the specs on the old and new motors; hardly different gear ratios,
yet no-load speeds 4 & 15 rpm (the latter says 11 rpm on its own sheet),
speed, torque & current at maximum efficiency 3.5 & 11 rpm, 5.85 & 2.13 Nm,
0.92 & 0.72 A. Still, the stall torques are roughly proportional to the gear
ratios and take slightly over 2A stall current, so the two motors are
probably the same type.

It would be interesting to know the running currents of the two
arrangements, and the current capacity of your power supply. I would have
expected the running current at twice the original speed to be double the
original.

As the thing starts up if you initialise it with maximum slack, perhaps you
could insert a flexible coupling between the drive and the driven shaft?
Perhaps a spring or rubber hose which would give the motor a chance to get
up to speed before hitting its running load.
--
Dave W

On Friday, 8 September 2017 15:07:55 UTC+1, www.GymRatZ.co.uk wrote:
On 08/09/2017 14:03, tabbypurr wrote:
On Friday, 8 September 2017 13:57:02 UTC+1, www.GymRatZ.co.uk wrote:

I've not seen any PTCs of low enough resistance, maybe someone else has.. Your psu is clearly not upto the motor's starting current. Probaly the simplest way to soft start it, if modding the psu isn't doable for you, would be with a light bulb & relay. The bulb is in series with the motor when power comes on, the relay shorts the bulb after 2 or 3 seconds using an RC delay to its coil.

I found the following:
http://www.mouser.co.uk/ProductDetai...8uws534N U%3d
or
https://tinyurl.com/y8p2upun

12 Ohm, 5 Amp NTC which I trust presume would limit start-up current to
2 Amps ?

Yes. It's a bit hard to believe anything that size would cope with 60W though. Maybe as a 1 off for 2ms while immersed in LN2.


NT

On Fri, 8 Sep 2017 13:56:53 +0100, "www.GymRatZ.co.uk"
wrote:

Or... am I braking up the wrong tree or is there another solution?
I suppose a beefier 24v supply would do the trick?

Beefier power supply.

Look for the manufacturer of the present one, and see waht they sell. I'd think
getting one that fits will ba harder than getting one with a bit more power.

Alternatively, get a DC motor controller in between the supply and the motor:
taken from the first random hit on ebay, "DC 10V~55V 12V 18V 24V 48V 30A PWM DC
Motor Speed Controller Soft Start Switch" is ~10 quid and has a speed cotrol
knob, in case that's useful.


Thomas Prufer

On Fri, 08 Sep 2017 13:56:53 +0100, www.GymRatZ.co.uk wrote:

Afternoon all.

I've got a drum filter (like a big washing machine) for the pond.
It's driven by a 24v worm-drive gearbox DC motor thing.
Earlier this year the motor/drive packed up so I replaced it with a
slightly faster turning unit as the original one was way too slow and
wasted loads of water.

The following page has all the the spec. etc.
http://www.motionco.co.uk/motors-wor...r-c-54_73.html

OEM unit was the last one on the list GMW40W0634 which I replaced with
GMW40W0505 - Speed and torque on the new unit are perfect however the
initial start-up current (apparently) of the new unit overloads the 24v
2A supply PSU causing it to shut down and re-start and so the on-going
cycle continues.

Manufacture has advised this doesn't happen on the correct unit (slow)
drive.

If I rotate the drum to take up the slack in the gears etc, on start-up
the drum rotates without any issues so presumably the fraction of a
second on no-load when the slack is taken up allows things to work
perfectly.

The following vid. is far more useful to demonstrate the issue.
https://www.dropbox.com/sh/iy1g8ddw2...qd5n4Q7OxVWBa?
dl=0
https://tinyurl.com/ybnzufb3

I want to stick with the new motor/gearbox because it's way more suited
to the drum cleaning operation and uses a fraction of the water to clean
a greater expanse of filter screen.
Could anyone suggest a suitable thermistor(?) to stick into the 24v
Motor feed that would limit the inrush current to not exceed the 2 Amp
cut-off of the PSU? (12 ohm ?)

Or... am I braking up the wrong tree or is there another solution?
I suppose a beefier 24v supply would do the trick?



Cheers All Pete


How about trying a 24v 21W wagon bulb in series with the motor? As the
motor is actually a nominal 12v unit with a max voltage of 24v you'd be
reducing the voltage a little but the starting surge would probably be
way down. If the motor isn't fast enough then try a second bulb in
parallel with the first.

On Friday, 8 September 2017 20:02:46 UTC+1, mick wrote:
On Fri, 08 Sep 2017 13:56:53 +0100, www.GymRatZ.co.uk wrote:

Afternoon all.

I've got a drum filter (like a big washing machine) for the pond.
It's driven by a 24v worm-drive gearbox DC motor thing.
Earlier this year the motor/drive packed up so I replaced it with a
slightly faster turning unit as the original one was way too slow and
wasted loads of water.

The following page has all the the spec. etc.
http://www.motionco.co.uk/motors-wor...r-c-54_73.html

OEM unit was the last one on the list GMW40W0634 which I replaced with
GMW40W0505 - Speed and torque on the new unit are perfect however the
initial start-up current (apparently) of the new unit overloads the 24v
2A supply PSU causing it to shut down and re-start and so the on-going
cycle continues.

Manufacture has advised this doesn't happen on the correct unit (slow)
drive.

If I rotate the drum to take up the slack in the gears etc, on start-up
the drum rotates without any issues so presumably the fraction of a
second on no-load when the slack is taken up allows things to work
perfectly.

The following vid. is far more useful to demonstrate the issue.
https://www.dropbox.com/sh/iy1g8ddw2...qd5n4Q7OxVWBa?
dl=0
https://tinyurl.com/ybnzufb3

I want to stick with the new motor/gearbox because it's way more suited
to the drum cleaning operation and uses a fraction of the water to clean
a greater expanse of filter screen.
Could anyone suggest a suitable thermistor(?) to stick into the 24v
Motor feed that would limit the inrush current to not exceed the 2 Amp
cut-off of the PSU? (12 ohm ?)

Or... am I braking up the wrong tree or is there another solution?
I suppose a beefier 24v supply would do the trick?



Cheers All Pete


How about trying a 24v 21W wagon bulb in series with the motor? As the
motor is actually a nominal 12v unit with a max voltage of 24v you'd be
reducing the voltage a little but the starting surge would probably be
way down. If the motor isn't fast enough then try a second bulb in
parallel with the first.

Need more power than that if the motor runs on 24v at about 2A.


NT

On 08/09/2017 15:11, Brian Gaff wrote:
A better supply. I'm not at all sure that a thermistor would be enough.
However you are in effect still using the same if not more current using
that method with the possibility under varying load of undesired strange
things going on.
Brian


Thanks Brian.
I guess for a few quid it might be interesting to try anyway just for
curiosity sake.

On 08/09/2017 13:56, www.GymRatZ.co.uk wrote:
Afternoon all.

I've got a drum filter (like a big washing machine) for the pond.
It's driven by a 24v worm-drive gearbox DC motor thing.
Earlier this year the motor/drive packed up so I replaced it with a
slightly faster turning unit as the original one was way too slow and
wasted loads of water.

The following page has all the the spec. etc.
http://www.motionco.co.uk/motors-wor...r-c-54_73.html

OEM unit was the last one on the list GMW40W0634 which I replaced with
GMW40W0505 - Speed and torque on the new unit are perfect however the
initial start-up current (apparently) of the new unit overloads the 24v
2A supply PSU causing it to shut down and re-start and so the on-going
cycle continues.

Manufacture has advised this doesn't happen on the correct unit (slow)
drive.

If I rotate the drum to take up the slack in the gears etc, on start-up
the drum rotates without any issues so presumably the fraction of a
second on no-load when the slack is taken up allows things to work
perfectly.

The following vid. is far more useful to demonstrate the issue.
https://www.dropbox.com/sh/iy1g8ddw2...4Q7OxVWBa?dl=0
https://tinyurl.com/ybnzufb3

I want to stick with the new motor/gearbox because it's way more suited
to the drum cleaning operation and uses a fraction of the water to clean
a greater expanse of filter screen.
Could anyone suggest a suitable thermistor(?) to stick into the 24v
Motor feed that would limit the inrush current to not exceed the 2 Amp
cut-off of the PSU? (12 ohm ?)

Or... am I braking up the wrong tree or is there another solution?
I suppose a beefier 24v supply would do the trick?

A beefier 24V supply would be the easiest solution!

I see the specs are at 12V for a 6-24V motor. I would estimate the stall
current to be 4.5A at 24V. The fact you see a start impulse suggests the
power supply is expecting a high initial load current but not 4.5A.

I feel the best way is to choose a hefty series resistor that limits the
initial surge and then a time delay relay to switch it out.

After looking up your thermister it can cope with the current, but fear
it will heat up very rapidly, sort of nullifying its effect. It might be
worth a try.

On 09/09/17 00:40, Fredxxx wrote:
After looking up your thermister it can cope with the current, but fear
it will heat up very rapidly, sort of nullifying its effect. It might be
worth a try.


why not add a bug ****off reservoir capacitor to cope with the surge?

Fredxxx wrote:

On 08/09/2017 13:56, www.GymRatZ.co.uk wrote:
Afternoon all.

I've got a drum filter (like a big washing machine) for the pond.
It's driven by a 24v worm-drive gearbox DC motor thing.
Earlier this year the motor/drive packed up so I replaced it with a
slightly faster turning unit as the original one was way too slow and
wasted loads of water.

The following page has all the the spec. etc.
http://www.motionco.co.uk/motors-wor...r-c-54_73.html

OEM unit was the last one on the list GMW40W0634 which I replaced with
GMW40W0505 - Speed and torque on the new unit are perfect however the
initial start-up current (apparently) of the new unit overloads the 24v
2A supply PSU causing it to shut down and re-start and so the on-going
cycle continues.

Manufacture has advised this doesn't happen on the correct unit (slow)
drive.

If I rotate the drum to take up the slack in the gears etc, on start-up
the drum rotates without any issues so presumably the fraction of a
second on no-load when the slack is taken up allows things to work
perfectly.

The following vid. is far more useful to demonstrate the issue.
https://www.dropbox.com/sh/iy1g8ddw2...4Q7OxVWBa?dl=0
https://tinyurl.com/ybnzufb3

I want to stick with the new motor/gearbox because it's way more suited
to the drum cleaning operation and uses a fraction of the water to clean
a greater expanse of filter screen.
Could anyone suggest a suitable thermistor(?) to stick into the 24v
Motor feed that would limit the inrush current to not exceed the 2 Amp
cut-off of the PSU? (12 ohm ?)

Or... am I braking up the wrong tree or is there another solution?
I suppose a beefier 24v supply would do the trick?

A beefier 24V supply would be the easiest solution!

I see the specs are at 12V for a 6-24V motor. I would estimate the stall
current to be 4.5A at 24V. The fact you see a start impulse suggests the
power supply is expecting a high initial load current but not 4.5A.

I feel the best way is to choose a hefty series resistor that limits the
initial surge and then a time delay relay to switch it out.

After looking up your thermister it can cope with the current, but fear
it will heat up very rapidly, sort of nullifying its effect. It might be
worth a try.

A problem with any of the methods of limiting starting current is that
the motor may stall with insufficient starting current. Then when the
relay/thermistor etc. switches in the full current it will still try to
take the full starting current (which the supply can't manage). And in
the meantime there is the risk of burning out the stalled motor.

--

Roger Hayter

On 09/09/17 09:10, Roger Hayter wrote:
Fredxxx wrote:

On 08/09/2017 13:56, www.GymRatZ.co.uk wrote:
Afternoon all.

I've got a drum filter (like a big washing machine) for the pond.
It's driven by a 24v worm-drive gearbox DC motor thing.
Earlier this year the motor/drive packed up so I replaced it with a
slightly faster turning unit as the original one was way too slow and
wasted loads of water.

The following page has all the the spec. etc.
http://www.motionco.co.uk/motors-wor...r-c-54_73.html

OEM unit was the last one on the list GMW40W0634 which I replaced with
GMW40W0505 - Speed and torque on the new unit are perfect however the
initial start-up current (apparently) of the new unit overloads the 24v
2A supply PSU causing it to shut down and re-start and so the on-going
cycle continues.

Manufacture has advised this doesn't happen on the correct unit (slow)
drive.

If I rotate the drum to take up the slack in the gears etc, on start-up
the drum rotates without any issues so presumably the fraction of a
second on no-load when the slack is taken up allows things to work
perfectly.

The following vid. is far more useful to demonstrate the issue.
https://www.dropbox.com/sh/iy1g8ddw2...4Q7OxVWBa?dl=0
https://tinyurl.com/ybnzufb3

I want to stick with the new motor/gearbox because it's way more suited
to the drum cleaning operation and uses a fraction of the water to clean
a greater expanse of filter screen.
Could anyone suggest a suitable thermistor(?) to stick into the 24v
Motor feed that would limit the inrush current to not exceed the 2 Amp
cut-off of the PSU? (12 ohm ?)

Or... am I braking up the wrong tree or is there another solution?
I suppose a beefier 24v supply would do the trick?

A beefier 24V supply would be the easiest solution!

I see the specs are at 12V for a 6-24V motor. I would estimate the stall
current to be 4.5A at 24V. The fact you see a start impulse suggests the
power supply is expecting a high initial load current but not 4.5A.

I feel the best way is to choose a hefty series resistor that limits the
initial surge and then a time delay relay to switch it out.

After looking up your thermister it can cope with the current, but fear
it will heat up very rapidly, sort of nullifying its effect. It might be
worth a try.

A problem with any of the methods of limiting starting current is that
the motor may stall with insufficient starting current. Then when the
relay/thermistor etc. switches in the full current it will still try to
take the full starting current (which the supply can't manage). And in
the meantime there is the risk of burning out the stalled motor.

So use a capacitor.


--
"When a true genius appears in the world, you may know him by this sign,
that the dunces are all in confederacy against him."

Jonathan Swift.

On Saturday, 9 September 2017 10:33:51 UTC+1, The Natural Philosopher wrote:
On 09/09/17 09:10, Roger Hayter wrote:
Fredxxx wrote:
On 08/09/2017 13:56, www.GymRatZ.co.uk wrote:
Afternoon all.

I've got a drum filter (like a big washing machine) for the pond.
It's driven by a 24v worm-drive gearbox DC motor thing.
Earlier this year the motor/drive packed up so I replaced it with a
slightly faster turning unit as the original one was way too slow and
wasted loads of water.

The following page has all the the spec. etc.
http://www.motionco.co.uk/motors-wor...r-c-54_73.html

OEM unit was the last one on the list GMW40W0634 which I replaced with
GMW40W0505 - Speed and torque on the new unit are perfect however the
initial start-up current (apparently) of the new unit overloads the 24v
2A supply PSU causing it to shut down and re-start and so the on-going
cycle continues.

Manufacture has advised this doesn't happen on the correct unit (slow)
drive.

If I rotate the drum to take up the slack in the gears etc, on start-up
the drum rotates without any issues so presumably the fraction of a
second on no-load when the slack is taken up allows things to work
perfectly.

The following vid. is far more useful to demonstrate the issue.
https://www.dropbox.com/sh/iy1g8ddw2...4Q7OxVWBa?dl=0
https://tinyurl.com/ybnzufb3

I want to stick with the new motor/gearbox because it's way more suited
to the drum cleaning operation and uses a fraction of the water to clean
a greater expanse of filter screen.
Could anyone suggest a suitable thermistor(?) to stick into the 24v
Motor feed that would limit the inrush current to not exceed the 2 Amp
cut-off of the PSU? (12 ohm ?)

Or... am I braking up the wrong tree or is there another solution?
I suppose a beefier 24v supply would do the trick?

A beefier 24V supply would be the easiest solution!

I see the specs are at 12V for a 6-24V motor. I would estimate the stall
current to be 4.5A at 24V. The fact you see a start impulse suggests the
power supply is expecting a high initial load current but not 4.5A.

I feel the best way is to choose a hefty series resistor that limits the
initial surge and then a time delay relay to switch it out.

After looking up your thermister it can cope with the current, but fear
it will heat up very rapidly, sort of nullifying its effect. It might be
worth a try.

A problem with any of the methods of limiting starting current is that
the motor may stall with insufficient starting current. Then when the
relay/thermistor etc. switches in the full current it will still try to
take the full starting current (which the supply can't manage). And in
the meantime there is the risk of burning out the stalled motor.

depends on the load profile of the motor. When you need full torque at start, don't do it. When torque = speed squared or cubed, do it.


So use a capacitor.

in which way?


NT

The Natural Philosopher wrote:

On 09/09/17 09:10, Roger Hayter wrote:
Fredxxx wrote:

On 08/09/2017 13:56, www.GymRatZ.co.uk wrote:
Afternoon all.

I've got a drum filter (like a big washing machine) for the pond.
It's driven by a 24v worm-drive gearbox DC motor thing.
Earlier this year the motor/drive packed up so I replaced it with a
slightly faster turning unit as the original one was way too slow and
wasted loads of water.

The following page has all the the spec. etc.
http://www.motionco.co.uk/motors-wor...r-c-54_73.html

OEM unit was the last one on the list GMW40W0634 which I replaced with
GMW40W0505 - Speed and torque on the new unit are perfect however the
initial start-up current (apparently) of the new unit overloads the 24v
2A supply PSU causing it to shut down and re-start and so the on-going
cycle continues.

Manufacture has advised this doesn't happen on the correct unit (slow)
drive.

If I rotate the drum to take up the slack in the gears etc, on start-up
the drum rotates without any issues so presumably the fraction of a
second on no-load when the slack is taken up allows things to work
perfectly.

The following vid. is far more useful to demonstrate the issue.
https://www.dropbox.com/sh/iy1g8ddw2...4Q7OxVWBa?dl=0
https://tinyurl.com/ybnzufb3

I want to stick with the new motor/gearbox because it's way more suited
to the drum cleaning operation and uses a fraction of the water to clean
a greater expanse of filter screen.
Could anyone suggest a suitable thermistor(?) to stick into the 24v
Motor feed that would limit the inrush current to not exceed the 2 Amp
cut-off of the PSU? (12 ohm ?)

Or... am I braking up the wrong tree or is there another solution?
I suppose a beefier 24v supply would do the trick?

A beefier 24V supply would be the easiest solution!

I see the specs are at 12V for a 6-24V motor. I would estimate the stall
current to be 4.5A at 24V. The fact you see a start impulse suggests the
power supply is expecting a high initial load current but not 4.5A.

I feel the best way is to choose a hefty series resistor that limits the
initial surge and then a time delay relay to switch it out.

After looking up your thermister it can cope with the current, but fear
it will heat up very rapidly, sort of nullifying its effect. It might be
worth a try.

A problem with any of the methods of limiting starting current is that
the motor may stall with insufficient starting current. Then when the
relay/thermistor etc. switches in the full current it will still try to
take the full starting current (which the supply can't manage). And in
the meantime there is the risk of burning out the stalled motor.

So use a capacitor.

Presumably in the realm of a several Farad supercapacitor, with a
somewhat complex slow pre-charging circuit before the load is switched
on. What about a battery? It would be cheaper and could be left
charged, avoiding the need for a special starting circuit. Solutions
not often seen as usually a higher peak current power supply would be
the more economical answer.



--

Roger Hayter

On 09/09/2017 05:18, Tjoepstil wrote:
On 09/09/17 00:40, Fredxxx wrote:
After looking up your thermister it can cope with the current, but
fear it will heat up very rapidly, sort of nullifying its effect. It
might be worth a try.


why not add a bug ****off reservoir capacitor to cope with the surge?

Have you looked at the size of the capacitor to cope with say a 5V droop
for 4 Amps for say 1 second?

Are you recommending one of these?

http://uk.farnell.com/vishay/mal2101...rew/dp/2309172

On 09/09/2017 09:10, Roger Hayter wrote:
Fredxxx wrote:

On 08/09/2017 13:56, www.GymRatZ.co.uk wrote:
Afternoon all.

I've got a drum filter (like a big washing machine) for the pond.
It's driven by a 24v worm-drive gearbox DC motor thing.
Earlier this year the motor/drive packed up so I replaced it with a
slightly faster turning unit as the original one was way too slow and
wasted loads of water.

The following page has all the the spec. etc.
http://www.motionco.co.uk/motors-wor...r-c-54_73.html

OEM unit was the last one on the list GMW40W0634 which I replaced with
GMW40W0505 - Speed and torque on the new unit are perfect however the
initial start-up current (apparently) of the new unit overloads the 24v
2A supply PSU causing it to shut down and re-start and so the on-going
cycle continues.

Manufacture has advised this doesn't happen on the correct unit (slow)
drive.

If I rotate the drum to take up the slack in the gears etc, on start-up
the drum rotates without any issues so presumably the fraction of a
second on no-load when the slack is taken up allows things to work
perfectly.

The following vid. is far more useful to demonstrate the issue.
https://www.dropbox.com/sh/iy1g8ddw2...4Q7OxVWBa?dl=0
https://tinyurl.com/ybnzufb3

I want to stick with the new motor/gearbox because it's way more suited
to the drum cleaning operation and uses a fraction of the water to clean
a greater expanse of filter screen.
Could anyone suggest a suitable thermistor(?) to stick into the 24v
Motor feed that would limit the inrush current to not exceed the 2 Amp
cut-off of the PSU? (12 ohm ?)

Or... am I braking up the wrong tree or is there another solution?
I suppose a beefier 24v supply would do the trick?

A beefier 24V supply would be the easiest solution!

I see the specs are at 12V for a 6-24V motor. I would estimate the stall
current to be 4.5A at 24V. The fact you see a start impulse suggests the
power supply is expecting a high initial load current but not 4.5A.

I feel the best way is to choose a hefty series resistor that limits the
initial surge and then a time delay relay to switch it out.

After looking up your thermister it can cope with the current, but fear
it will heat up very rapidly, sort of nullifying its effect. It might be
worth a try.

A problem with any of the methods of limiting starting current is that
the motor may stall with insufficient starting current. Then when the
relay/thermistor etc. switches in the full current it will still try to
take the full starting current (which the supply can't manage). And in
the meantime there is the risk of burning out the stalled motor.

For a DC motor, torque is propoprtional to current. The system that Pete
has put together, going by the video, doesn't seem to have a increased
startup torque apart from the effects of inertia and speed up.

He demonstrates than a significant load on the filter doesn't put the
power supply into fail mode.

Therefore I don't see 'stall' from a limited starting current an issue.
If this was an induction motor then I would agree with you which has a
more complicated torque vs speed vs current.

On 09/09/2017 12:23, Roger Hayter wrote:
The Natural Philosopher wrote:

On 09/09/17 09:10, Roger Hayter wrote:
Fredxxx wrote:

On 08/09/2017 13:56, www.GymRatZ.co.uk wrote:
Afternoon all.

I've got a drum filter (like a big washing machine) for the pond.
It's driven by a 24v worm-drive gearbox DC motor thing.
Earlier this year the motor/drive packed up so I replaced it with a
slightly faster turning unit as the original one was way too slow and
wasted loads of water.

The following page has all the the spec. etc.
http://www.motionco.co.uk/motors-wor...r-c-54_73.html

OEM unit was the last one on the list GMW40W0634 which I replaced with
GMW40W0505 - Speed and torque on the new unit are perfect however the
initial start-up current (apparently) of the new unit overloads the 24v
2A supply PSU causing it to shut down and re-start and so the on-going
cycle continues.

Manufacture has advised this doesn't happen on the correct unit (slow)
drive.

If I rotate the drum to take up the slack in the gears etc, on start-up
the drum rotates without any issues so presumably the fraction of a
second on no-load when the slack is taken up allows things to work
perfectly.

The following vid. is far more useful to demonstrate the issue.
https://www.dropbox.com/sh/iy1g8ddw2...4Q7OxVWBa?dl=0
https://tinyurl.com/ybnzufb3

I want to stick with the new motor/gearbox because it's way more suited
to the drum cleaning operation and uses a fraction of the water to clean
a greater expanse of filter screen.
Could anyone suggest a suitable thermistor(?) to stick into the 24v
Motor feed that would limit the inrush current to not exceed the 2 Amp
cut-off of the PSU? (12 ohm ?)

Or... am I braking up the wrong tree or is there another solution?
I suppose a beefier 24v supply would do the trick?

A beefier 24V supply would be the easiest solution!

I see the specs are at 12V for a 6-24V motor. I would estimate the stall
current to be 4.5A at 24V. The fact you see a start impulse suggests the
power supply is expecting a high initial load current but not 4.5A.

I feel the best way is to choose a hefty series resistor that limits the
initial surge and then a time delay relay to switch it out.

After looking up your thermister it can cope with the current, but fear
it will heat up very rapidly, sort of nullifying its effect. It might be
worth a try.

A problem with any of the methods of limiting starting current is that
the motor may stall with insufficient starting current. Then when the
relay/thermistor etc. switches in the full current it will still try to
take the full starting current (which the supply can't manage). And in
the meantime there is the risk of burning out the stalled motor.

So use a capacitor.

Presumably in the realm of a several Farad supercapacitor, with a
somewhat complex slow pre-charging circuit before the load is switched
on. What about a battery? It would be cheaper and could be left
charged, avoiding the need for a special starting circuit. Solutions
not often seen as usually a higher peak current power supply would be
the more economical answer.

I hadn't thought of a battery. The power supply would need to be 27V or
so to float charge the batteries. I doubt there is any adjustment? It's
also 3V over the motor voltage rating.

Another way is to use a 12V battery with a diode to get the motor
running at 1/2 speed for the 24V supply to then override. Then apply a
small trickle charge to the battery.

wrote:

On Saturday, 9 September 2017 10:33:51 UTC+1, The Natural Philosopher
wrote: On 09/09/17 09:10, Roger Hayter wrote: Fredxxx
wrote: On 08/09/2017 13:56, www.GymRatZ.co.uk
wrote: Afternoon all. I've got a drum filter (like a big
washing machine) for the pond. It's driven by a 24v worm-drive
gearbox DC motor thing. Earlier this year the motor/drive packed up
so I replaced it with a slightly faster turning unit as the original
one was way too slow and wasted loads of water. The
following page has all the the spec. etc.
http://www.motionco.co.uk/motors-wor...r-c-54_73.html
OEM unit was the last one on the list GMW40W0634 which I replaced
with GMW40W0505 - Speed and torque on the new unit are perfect
however the initial start-up current (apparently) of the new unit
overloads the 24v 2A supply PSU causing it to shut down and re-start
and so the on-going cycle continues. Manufacture has
advised this doesn't happen on the correct unit (slow) drive.
If I rotate the drum to take up the slack in the gears etc, on
start-up the drum rotates without any issues so presumably the
fraction of a second on no-load when the slack is taken up allows
things to work perfectly. The following vid. is far more
useful to demonstrate the issue.
https://www.dropbox.com/sh/iy1g8ddw2...4Q7OxVWBa?dl=0
https://tinyurl.com/ybnzufb3 I want to stick with the
new motor/gearbox because it's way more suited to the drum cleaning
operation and uses a fraction of the water to clean a greater
expanse of filter screen. Could anyone suggest a suitable
thermistor(?) to stick into the 24v Motor feed that would limit the
inrush current to not exceed the 2 Amp cut-off of the PSU? (12 ohm
?) Or... am I braking up the wrong tree or is there another
solution? I suppose a beefier 24v supply would do the trick?
A beefier 24V supply would be the easiest solution! I see the
specs are at 12V for a 6-24V motor. I would estimate the stall
current to be 4.5A at 24V. The fact you see a start impulse suggests the
power supply is expecting a high initial load current but not 4.5A.
I feel the best way is to choose a hefty series resistor that
limits the initial surge and then a time delay relay to switch it
out. After looking up your thermister it can cope with the
current, but fear it will heat up very rapidly, sort of nullifying
its effect. It might be worth a try. A problem with any of
the methods of limiting starting current is that the motor may stall
with insufficient starting current. Then when the relay/thermistor
etc. switches in the full current it will still try to take the full
starting current (which the supply can't manage). And in the meantime
there is the risk of burning out the stalled motor.

depends on the load profile of the motor. When you need full torque at
start, don't do it. When torque = speed squared or cubed, do it.



The OP describes overcoming the inertia of a large drum whch the motor
has to start rotating, quite likely with fairly crude bearings adding to
the starting force. So it probably is much higher torque when starting
than when running at working speed.







So use a capacitor.

in which way?


NT


--

Roger Hayter

On 09/09/17 13:05, Fredxxx wrote:
On 09/09/2017 05:18, Tjoepstil wrote:
On 09/09/17 00:40, Fredxxx wrote:
After looking up your thermister it can cope with the current, but
fear it will heat up very rapidly, sort of nullifying its effect. It
might be worth a try.


why not add a bug ****off reservoir capacitor to cope with the surge?

Have you looked at the size of the capacitor to cope with say a 5V droop
for 4 Amps for say 1 second?

Are you recommending one of these?

http://uk.farnell.com/vishay/mal2101...rew/dp/2309172

Id sat more like

http://uk.farnell.com/kemet/fs1b105z...ial/dp/2777892

One farad is quite a kicker

have a bit of series resistor to limit peak current, and then the motor
gets full crack to start and a resistor to limit its running current.


--
"I am inclined to tell the truth and dislike people who lie consistently.
This makes me unfit for the company of people of a Left persuasion, and
all women"

On 09/09/17 13:12, Roger Hayter wrote:
wrote:

On Saturday, 9 September 2017 10:33:51 UTC+1, The Natural Philosopher
wrote: On 09/09/17 09:10, Roger Hayter wrote: Fredxxx
wrote: On 08/09/2017 13:56, www.GymRatZ.co.uk
wrote: Afternoon all. I've got a drum filter (like a big
washing machine) for the pond. It's driven by a 24v worm-drive
gearbox DC motor thing. Earlier this year the motor/drive packed up
so I replaced it with a slightly faster turning unit as the original
one was way too slow and wasted loads of water. The
following page has all the the spec. etc.
http://www.motionco.co.uk/motors-wor...r-c-54_73.html
OEM unit was the last one on the list GMW40W0634 which I replaced
with GMW40W0505 - Speed and torque on the new unit are perfect
however the initial start-up current (apparently) of the new unit
overloads the 24v 2A supply PSU causing it to shut down and re-start
and so the on-going cycle continues. Manufacture has
advised this doesn't happen on the correct unit (slow) drive.
If I rotate the drum to take up the slack in the gears etc, on
start-up the drum rotates without any issues so presumably the
fraction of a second on no-load when the slack is taken up allows
things to work perfectly. The following vid. is far more
useful to demonstrate the issue.
https://www.dropbox.com/sh/iy1g8ddw2...4Q7OxVWBa?dl=0
https://tinyurl.com/ybnzufb3 I want to stick with the
new motor/gearbox because it's way more suited to the drum cleaning
operation and uses a fraction of the water to clean a greater
expanse of filter screen. Could anyone suggest a suitable
thermistor(?) to stick into the 24v Motor feed that would limit the
inrush current to not exceed the 2 Amp cut-off of the PSU? (12 ohm
?) Or... am I braking up the wrong tree or is there another
solution? I suppose a beefier 24v supply would do the trick?
A beefier 24V supply would be the easiest solution! I see the
specs are at 12V for a 6-24V motor. I would estimate the stall
current to be 4.5A at 24V. The fact you see a start impulse suggests the
power supply is expecting a high initial load current but not 4.5A.
I feel the best way is to choose a hefty series resistor that
limits the initial surge and then a time delay relay to switch it
out. After looking up your thermister it can cope with the
current, but fear it will heat up very rapidly, sort of nullifying
its effect. It might be worth a try. A problem with any of
the methods of limiting starting current is that the motor may stall
with insufficient starting current. Then when the relay/thermistor
etc. switches in the full current it will still try to take the full
starting current (which the supply can't manage). And in the meantime
there is the risk of burning out the stalled motor.

depends on the load profile of the motor. When you need full torque at
start, don't do it. When torque = speed squared or cubed, do it.



The OP describes overcoming the inertia of a large drum whch the motor
has to start rotating, quite likely with fairly crude bearings adding to
the starting force. So it probably is much higher torque when starting
than when running at working speed.


accelerating the motor armature takes a lot of extra torque.

Strall or start current on a REALLY good motor takes massive current -
there is almost no interneal resistance.

cheaper motors have more resistive losses.

Its a common issue on model car racing.

And indeed electric powored models of all sorts

Typical solutions inbclude chopped supplys with series chokes to limit
start up current, and supercaps to give a 'drag race start' on on car
motors. Though these are generally used to decrease battery imnpedance
for a split second ..i.e upstream of the actual controller, rather than
across the motor.









So use a capacitor.

in which way?


NT




--
The New Left are the people they warned you about.

On Fri, 08 Sep 2017 13:56:53 +0100, www.GymRatZ.co.uk wrote:

Afternoon all.

I've got a drum filter (like a big washing machine) for the pond.
It's driven by a 24v worm-drive gearbox DC motor thing.
Earlier this year the motor/drive packed up so I replaced it with a
slightly faster turning unit as the original one was way too slow and
wasted loads of water.

The following page has all the the spec. etc.
http://www.motionco.co.uk/motors-wor...r-c-54_73.html

OEM unit was the last one on the list GMW40W0634 which I replaced with
GMW40W0505 - Speed and torque on the new unit are perfect however the
initial start-up current (apparently) of the new unit overloads the 24v
2A supply PSU causing it to shut down and re-start and so the on-going
cycle continues.

Manufacture has advised this doesn't happen on the correct unit (slow)
drive.

If I rotate the drum to take up the slack in the gears etc, on start-up
the drum rotates without any issues so presumably the fraction of a
second on no-load when the slack is taken up allows things to work
perfectly.

The following vid. is far more useful to demonstrate the issue.
https://www.dropbox.com/sh/iy1g8ddw2...qd5n4Q7OxVWBa?
dl=0
https://tinyurl.com/ybnzufb3

I want to stick with the new motor/gearbox because it's way more suited
to the drum cleaning operation and uses a fraction of the water to clean
a greater expanse of filter screen.
Could anyone suggest a suitable thermistor(?) to stick into the 24v
Motor feed that would limit the inrush current to not exceed the 2 Amp
cut-off of the PSU? (12 ohm ?)

Or... am I braking up the wrong tree or is there another solution?
I suppose a beefier 24v supply would do the trick?


After looking at all the other follow up postings, it seems to me that
the replacement drive motor unit must be just about doubling up on the
power demanded by the original unit. Whilst you've demonstrated that the
existing PSU (presumably, according to your description of its behaviour
in response to the start up overload, a switch mode type) is capable of
providing the power required to keep it running once up to speed, it's
patently obvious that its specification is now far too marginal for that
uprated motor/gearbox unit.

If the PSU is of any significant age (say 2 or 3 years of continuous
duty), it could simply be that the HT smoothing cap, typically a 400vdc
rated one in the region of 50 to 100 microfarad for a 50VA smpsu, might
simply be overdue for replacement. The symptoms are also classic of a
dried out HT smoothing cap as well as the effect of trying to use an
under-specced PSU.

Unless you're used to dealing with smpsu repairs and have suitable
components to hand (eg. a 100 microFarad 400vdc rated cap), I'd recommend
replacing the PSU with a higher output current rating unit (say 3 to 4
amp - you might not necessarily need to double up on the original PSU
spec, that 2A rating may simply have been the handiest off the shelf
substitute for a minimum of 1.45A that may have originally been called
for by the designers).

--
Johnny B Good

Trying to think of a mechanical solution!

DerbyBorn wrote

Trying to think of a mechanical solution!

More fool you. The world has moved on.

On Sun, 10 Sep 2017 09:29:06 GMT, DerbyBorn
wrote:




Trying to think of a mechanical solution!

Don't even think about it!

You will be operating on a wing & a prayer, even if the system works a
bit of cold weather or maybe a slight fall in PSU efficiency will tip
the balance.

The tables are for 12V

At 24V the stall current will be considerably higher.

You will have to get the stall current rating at 24V from the
manufacturer and select a supply to suit. Might be problems here
though as they would probably not wish to depart from or expand on
published data.

You could of course get hold of a supply, or 24V battery and measure
the stall current. [Use a fuse and dont dally with the measurement].

If you go in "blind" and want to be sure, then a 24V 10A SMPS from
Ebay shouldn't break the bank.

I bought a few of varying Voltages and currents, the prices are
unbelievable in comparison to what they once cost.

AB

On 10/09/2017 10:29, DerbyBorn wrote:


Trying to think of a mechanical solution!


Van Doorne style automatic gearbox?

On Sun, 10 Sep 2017 12:57:47 +0100, lid wrote:

On 10/09/2017 10:29, DerbyBorn wrote:


Trying to think of a mechanical solution!


Van Doorne style automatic gearbox?

I think you have the wrong idea.

Before you initiate the start sequence of the mechanical contraption
the motor is stalled.

The motor is stalled if you glue it with Araldite,

The motor is stalled if you gear the thing up so the output shaft
rotates at near relatavsitic speeds,

The motor is stalled if you replace it with a gear train that takes
more than a human lifetime to complete an output shaft rotation.

The motor on its own is stalled, it is stationary, it generates no
back EMF.

Discounting inductive reactance the situation boils down to I = V/R

Unless your gearbox is so intelligent that it can spin the motor up
before power is applied, the the problem is electrical.

The condition could be catered for fairly easily from an electrical
perspective, but it's far simpler and more cost effective to buy a
bigger PSU. A larger PSU would also have the ability to maintain
operation if any increase in mechanical load occured.

Gear replacement cannot be a serious option anyway, the costs are
outlandish.

AB

On 10/09/2017 14:04, Archibald Tarquin Blenkinsopp wrote:
On Sun, 10 Sep 2017 12:57:47 +0100, lid wrote:

On 10/09/2017 10:29, DerbyBorn wrote:


Trying to think of a mechanical solution!


Van Doorne style automatic gearbox?

I think you have the wrong idea.

Before you initiate the start sequence of the mechanical contraption
the motor is stalled.

The motor is stalled if you glue it with Araldite,

The motor is stalled if you gear the thing up so the output shaft
rotates at near relatavsitic speeds,

The motor is stalled if you replace it with a gear train that takes
more than a human lifetime to complete an output shaft rotation.

The motor on its own is stalled, it is stationary, it generates no
back EMF.

Discounting inductive reactance the situation boils down to I = V/R

Unless your gearbox is so intelligent that it can spin the motor up
before power is applied, the the problem is electrical.

The power supply seems able to supply a start current for a split second
before switching off. The filter even rotates a small distance.

In this case I agree a mechanical solution is not an economic one.

I do feel the easiest mechanical solution would have been to have a
centrifugal clutch, but hey that's still more expensive than a power
supply or series resistor.

On Sun, 10 Sep 2017 14:57:35 +0100, Fredxxx wrote:

On 10/09/2017 14:04, Archibald Tarquin Blenkinsopp wrote:
On Sun, 10 Sep 2017 12:57:47 +0100, lid wrote:

On 10/09/2017 10:29, DerbyBorn wrote:


Trying to think of a mechanical solution!


Van Doorne style automatic gearbox?

I think you have the wrong idea.

Before you initiate the start sequence of the mechanical contraption
the motor is stalled.

The motor is stalled if you glue it with Araldite,

The motor is stalled if you gear the thing up so the output shaft
rotates at near relatavsitic speeds,

The motor is stalled if you replace it with a gear train that takes
more than a human lifetime to complete an output shaft rotation.

The motor on its own is stalled, it is stationary, it generates no
back EMF.

Discounting inductive reactance the situation boils down to I = V/R

Unless your gearbox is so intelligent that it can spin the motor up
before power is applied, the the problem is electrical.

The power supply seems able to supply a start current for a split second
before switching off. The filter even rotates a small distance.

In this case I agree a mechanical solution is not an economic one.

I do feel the easiest mechanical solution would have been to have a
centrifugal clutch, but hey that's still more expensive than a power
supply or series resistor.

The PSU is overcurrent protected.

Electronic overcurrent protection has to actually detect overcurrent
to operate.

When it detects overcurrent it folds back or shuts down the output.

Not exactly "rocket science".

If you then think things through very carefully, you will realise that
the excess current flow must still adhere to the laws of physics,
hence the magnetic flux and resulting brief movement.

Clutch? Resistor?

That would be a systematic problem with the UK educational system.

Brexit is another example.

AB

On 10/09/2017 14:04, Archibald Tarquin Blenkinsopp wrote:
On Sun, 10 Sep 2017 12:57:47 +0100, lid wrote:

On 10/09/2017 10:29, DerbyBorn wrote:


Trying to think of a mechanical solution!


Van Doorne style automatic gearbox?

I think you have the wrong idea.

Before you initiate the start sequence of the mechanical contraption
the motor is stalled.

The motor is stalled if you glue it with Araldite,

The motor is stalled if you gear the thing up so the output shaft
rotates at near relatavsitic speeds,

The motor is stalled if you replace it with a gear train that takes
more than a human lifetime to complete an output shaft rotation.

The motor on its own is stalled, it is stationary, it generates no
back EMF.

Discounting inductive reactance the situation boils down to I = V/R

Unless your gearbox is so intelligent that it can spin the motor up
before power is applied, the the problem is electrical.

The condition could be catered for fairly easily from an electrical
perspective, but it's far simpler and more cost effective to buy a
bigger PSU. A larger PSU would also have the ability to maintain
operation if any increase in mechanical load occured.

Gear replacement cannot be a serious option anyway, the costs are
outlandish.

AB




Don't disagree with any of that, but presumably an external load will
alter the area under the initial bit of the current/time curve, so that
a PSU with some capacitance in the output might succeed in starting the
motor if it were more lightly loaded.

My suggestion was, of course, largely facetious, but I've always
wondered whether such a gearbox could be cobbled up out of an old fan
belt and some split pulleys...

On Sun, 10 Sep 2017 16:28:27 +0100, lid wrote:

On 10/09/2017 14:04, Archibald Tarquin Blenkinsopp wrote:
On Sun, 10 Sep 2017 12:57:47 +0100, lid wrote:

On 10/09/2017 10:29, DerbyBorn wrote:


Trying to think of a mechanical solution!


Van Doorne style automatic gearbox?

I think you have the wrong idea.

Before you initiate the start sequence of the mechanical contraption
the motor is stalled.

The motor is stalled if you glue it with Araldite,

The motor is stalled if you gear the thing up so the output shaft
rotates at near relatavsitic speeds,

The motor is stalled if you replace it with a gear train that takes
more than a human lifetime to complete an output shaft rotation.

The motor on its own is stalled, it is stationary, it generates no
back EMF.

Discounting inductive reactance the situation boils down to I = V/R

Unless your gearbox is so intelligent that it can spin the motor up
before power is applied, the the problem is electrical.

The condition could be catered for fairly easily from an electrical
perspective, but it's far simpler and more cost effective to buy a
bigger PSU. A larger PSU would also have the ability to maintain
operation if any increase in mechanical load occured.

Gear replacement cannot be a serious option anyway, the costs are
outlandish.

AB




Don't disagree with any of that, but presumably an external load will
alter the area under the initial bit of the current/time curve, so that
a PSU with some capacitance in the output might succeed in starting the
motor if it were more lightly loaded.

My suggestion was, of course, largely facetious, but I've always
wondered whether such a gearbox could be cobbled up out of an old fan
belt and some split pulleys...

You would probably find that a series resistor would drop the Voltage
too low to enable the motor to turn, all the power would go to warming
the resistor. It could be tried but I wouldn't even go to the trouble
of opening the components drawer personally.

Capacitance is the answer, charge a very large capacitor via a
resistor of course then after a time period to allow the charge to be
developed switch the load in.

The trouble is the sequence would be power up the SMPS, wait, Switch
in the load to the charged capacitor, wait briefly while the motor
starts, switch the motor over to the SMPS output.

Timers, Relays, Damn big capacitor, time to assemble box up etc.

Obviously it is difficult to be absolutely precise, but it is
virtually certain that the overcurrent event occurs well before the
motor has a chance to build the speed up to provide the back EMF even
under no load conditions. The PSU will no doubt give a much higher
current than the rating states, but as soon as the overcurrent is
detected the output will fold back or shut down. This has to be fairly
fast in order to protect the semiconductors.

Hence the simple almost zero uncertainty solution, a bigger PSU.


AB

DerbyBorn wrote :


Trying to think of a mechanical solution!

The very weak start up torque of electric clock motors, used a fine
hair spring between the motor output shaft and the gearing drive.

On Sun, 10 Sep 2017 17:58:49 +0100, Harry Bloomfield
wrote:

DerbyBorn wrote :


Trying to think of a mechanical solution!

The very weak start up torque of electric clock motors, used a fine
hair spring between the motor output shaft and the gearing drive.

To prevent a grid shutdown?

AB

On 10/09/2017 16:26, Archibald Tarquin Blenkinsopp wrote:
On Sun, 10 Sep 2017 14:57:35 +0100, Fredxxx wrote:

On 10/09/2017 14:04, Archibald Tarquin Blenkinsopp wrote:
On Sun, 10 Sep 2017 12:57:47 +0100, lid wrote:

On 10/09/2017 10:29, DerbyBorn wrote:


Trying to think of a mechanical solution!


Van Doorne style automatic gearbox?

I think you have the wrong idea.

Before you initiate the start sequence of the mechanical contraption
the motor is stalled.

The motor is stalled if you glue it with Araldite,

The motor is stalled if you gear the thing up so the output shaft
rotates at near relatavsitic speeds,

The motor is stalled if you replace it with a gear train that takes
more than a human lifetime to complete an output shaft rotation.

The motor on its own is stalled, it is stationary, it generates no
back EMF.

Discounting inductive reactance the situation boils down to I = V/R

Unless your gearbox is so intelligent that it can spin the motor up
before power is applied, the the problem is electrical.

The power supply seems able to supply a start current for a split second
before switching off. The filter even rotates a small distance.

In this case I agree a mechanical solution is not an economic one.

I do feel the easiest mechanical solution would have been to have a
centrifugal clutch, but hey that's still more expensive than a power
supply or series resistor.

The PSU is overcurrent protected.

The protection seems to kick-in after a short time.

Electronic overcurrent protection has to actually detect overcurrent
to operate.

Ones that are sensitive to overcurrrent, tend to ramp up the voltage in
a controlled way.

When it detects overcurrent it folds back or shuts down the output.

Not exactly "rocket science".

Of course, but the time to shutdown, and the level of overcurrent to
cause shutdown are unknowns.

If you then think things through very carefully, you will realise that
the excess current flow must still adhere to the laws of physics,
hence the magnetic flux and resulting brief movement.

Clutch? Resistor?

You seem to dispense with the 'resistor' yet is the cheapest and
simplest method of reducing current. We might find that adding 1ohm to
the circuit is all that is need for a start without a shutdown. 1ohm at
running current will be at most a 2V drop with a 10% drop in speed.

That would be a systematic problem with the UK educational system.

Brexit is another example.

A condescending loser Remoaner. I could guess from your post.

On 10/09/2017 16:26, Archibald Tarquin Blenkinsopp wrote:
On Sun, 10 Sep 2017 14:57:35 +0100, Fredxxx wrote:

On 10/09/2017 14:04, Archibald Tarquin Blenkinsopp wrote:
On Sun, 10 Sep 2017 12:57:47 +0100, lid wrote:

On 10/09/2017 10:29, DerbyBorn wrote:


Trying to think of a mechanical solution!


Van Doorne style automatic gearbox?

I think you have the wrong idea.

Before you initiate the start sequence of the mechanical contraption
the motor is stalled.

The motor is stalled if you glue it with Araldite,

The motor is stalled if you gear the thing up so the output shaft
rotates at near relatavsitic speeds,

The motor is stalled if you replace it with a gear train that takes
more than a human lifetime to complete an output shaft rotation.

The motor on its own is stalled, it is stationary, it generates no
back EMF.

Discounting inductive reactance the situation boils down to I = V/R

Unless your gearbox is so intelligent that it can spin the motor up
before power is applied, the the problem is electrical.

The power supply seems able to supply a start current for a split second
before switching off. The filter even rotates a small distance.

In this case I agree a mechanical solution is not an economic one.

I do feel the easiest mechanical solution would have been to have a
centrifugal clutch, but hey that's still more expensive than a power
supply or series resistor.

The PSU is overcurrent protected.

The protection seems to kick-in after a short time.

Electronic overcurrent protection has to actually detect overcurrent
to operate.

Ones that are sensitive to overcurrrent, tend to ramp up the voltage in
a controlled way.

When it detects overcurrent it folds back or shuts down the output.

Not exactly "rocket science".

Of course, but the time to shutdown, and the level of overcurrent to
cause shutdown are unknowns.

If you then think things through very carefully, you will realise that
the excess current flow must still adhere to the laws of physics,
hence the magnetic flux and resulting brief movement.

If you think even more carefully you will realise it is possible to have
a very fast shutdown.

Clutch? Resistor?

You seem to dispense with the 'resistor' yet is the cheapest and
simplest method of reducing current. We might find that adding 1ohm to
the circuit is all that is need for a start without a shutdown. 1ohm at
running current will be at most a 2V drop with a 10% drop in speed.

That would be a systematic problem with the UK educational system.

Brexit is another example.

Clearly a loser Remoaner. I could guess from your post.

On Sun, 10 Sep 2017 22:23:44 +0100, Fredxxx wrote:

On 10/09/2017 16:26, Archibald Tarquin Blenkinsopp wrote:
On Sun, 10 Sep 2017 14:57:35 +0100, Fredxxx wrote:

On 10/09/2017 14:04, Archibald Tarquin Blenkinsopp wrote:
On Sun, 10 Sep 2017 12:57:47 +0100, lid wrote:

On 10/09/2017 10:29, DerbyBorn wrote:


Trying to think of a mechanical solution!


Van Doorne style automatic gearbox?

I think you have the wrong idea.

Before you initiate the start sequence of the mechanical contraption
the motor is stalled.

The motor is stalled if you glue it with Araldite,

The motor is stalled if you gear the thing up so the output shaft
rotates at near relatavsitic speeds,

The motor is stalled if you replace it with a gear train that takes
more than a human lifetime to complete an output shaft rotation.

The motor on its own is stalled, it is stationary, it generates no
back EMF.

Discounting inductive reactance the situation boils down to I = V/R

Unless your gearbox is so intelligent that it can spin the motor up
before power is applied, the the problem is electrical.

The power supply seems able to supply a start current for a split second
before switching off. The filter even rotates a small distance.

In this case I agree a mechanical solution is not an economic one.

I do feel the easiest mechanical solution would have been to have a
centrifugal clutch, but hey that's still more expensive than a power
supply or series resistor.

The PSU is overcurrent protected.

The protection seems to kick-in after a short time.

Electronic overcurrent protection has to actually detect overcurrent
to operate.

Ones that are sensitive to overcurrrent, tend to ramp up the voltage in
a controlled way.

When it detects overcurrent it folds back or shuts down the output.

Not exactly "rocket science".

Of course, but the time to shutdown, and the level of overcurrent to
cause shutdown are unknowns.

If you then think things through very carefully, you will realise that
the excess current flow must still adhere to the laws of physics,
hence the magnetic flux and resulting brief movement.

If you think even more carefully you will realise it is possible to have
a very fast shutdown.

Really? You have to sense the overcurrent first. There has to be a lag
to prevent nuisance tripping otherwise every minor glitch would
trigger a shutdown.


Clutch? Resistor?

You seem to dispense with the 'resistor' yet is the cheapest and
simplest method of reducing current. We might find that adding 1ohm to
the circuit is all that is need for a start without a shutdown. 1ohm at
running current will be at most a 2V drop with a 10% drop in speed.

Running current?

If the motor was running you wouldn't need a resistor. If you add
resistance the motor wont move, if it could move on a lower current it
wouldn't be tripping now would it?

AB

That would be a systematic problem with the UK educational system.

Brexit is another example.

Clearly a loser Remoaner. I could guess from your post.

Not a loser, not a remoaner. I think the EU is better off without
Britain. Britain was kept out for a long time before Heath managed to
worm his way in.

Whatever is said by Junker & friends I would guess that they are more
than happy to see the back of the UK.

I certainly will not lose, I'm stciking firmly with the EU. The losers
are going in another direction, what that direction is, they haven't a
clue.


AB

On 10/09/2017 23:26, Archibald Tarquin Blenkinsopp wrote:
On Sun, 10 Sep 2017 22:23:44 +0100, Fredxxx wrote:

On 10/09/2017 16:26, Archibald Tarquin Blenkinsopp wrote:
On Sun, 10 Sep 2017 14:57:35 +0100, Fredxxx wrote:

On 10/09/2017 14:04, Archibald Tarquin Blenkinsopp wrote:
On Sun, 10 Sep 2017 12:57:47 +0100, lid wrote:

On 10/09/2017 10:29, DerbyBorn wrote:


Trying to think of a mechanical solution!


Van Doorne style automatic gearbox?

I think you have the wrong idea.

Before you initiate the start sequence of the mechanical contraption
the motor is stalled.

The motor is stalled if you glue it with Araldite,

The motor is stalled if you gear the thing up so the output shaft
rotates at near relatavsitic speeds,

The motor is stalled if you replace it with a gear train that takes
more than a human lifetime to complete an output shaft rotation.

The motor on its own is stalled, it is stationary, it generates no
back EMF.

Discounting inductive reactance the situation boils down to I = V/R

Unless your gearbox is so intelligent that it can spin the motor up
before power is applied, the the problem is electrical.

The power supply seems able to supply a start current for a split second
before switching off. The filter even rotates a small distance.

In this case I agree a mechanical solution is not an economic one.

I do feel the easiest mechanical solution would have been to have a
centrifugal clutch, but hey that's still more expensive than a power
supply or series resistor.

The PSU is overcurrent protected.

The protection seems to kick-in after a short time.

Electronic overcurrent protection has to actually detect overcurrent
to operate.

Ones that are sensitive to overcurrrent, tend to ramp up the voltage in
a controlled way.

When it detects overcurrent it folds back or shuts down the output.

Not exactly "rocket science".

Of course, but the time to shutdown, and the level of overcurrent to
cause shutdown are unknowns.

If you then think things through very carefully, you will realise that
the excess current flow must still adhere to the laws of physics,
hence the magnetic flux and resulting brief movement.

If you think even more carefully you will realise it is possible to have
a very fast shutdown.

Really? You have to sense the overcurrent first. There has to be a lag
to prevent nuisance tripping otherwise every minor glitch would
trigger a shutdown.

I wouldn't call a 4 amp load a glitch, of any duration.

Clutch? Resistor?

You seem to dispense with the 'resistor' yet is the cheapest and
simplest method of reducing current. We might find that adding 1ohm to
the circuit is all that is need for a start without a shutdown. 1ohm at
running current will be at most a 2V drop with a 10% drop in speed.

Running current?

The datasheet gives specs of normal running current. The system in the
video implies there is very little load in normal running.

If the motor was running you wouldn't need a resistor. If you add
resistance the motor wont move, if it could move on a lower current it
wouldn't be tripping now would it?

I'm surprised you claim that. The issue is starting current that I
recall will be in the order of 4.5Amps and hence implies the motor has a
resistance of 5ohms. The running current should be a fraction of this.

AB

That would be a systematic problem with the UK educational system.

Brexit is another example.

Clearly a loser Remoaner. I could guess from your post.

Not a loser, not a remoaner. I think the EU is better off without
Britain. Britain was kept out for a long time before Heath managed to
worm his way in.

Whatever is said by Junker & friends I would guess that they are more
than happy to see the back of the UK.

I think they want to apply some pain and grief to the process in perhaps
a vindictive manner.

I certainly will not lose, I'm stciking firmly with the EU. The losers
are going in another direction, what that direction is, they haven't a
clue.

Apologies, it seems we have a sort of accord on this.

On Sun, 10 Sep 2017 17:58:49 +0100, Harry Bloomfield wrote:

DerbyBorn wrote :


Trying to think of a mechanical solution!

The very weak start up torque of electric clock motors, used a fine hair
spring between the motor output shaft and the gearing drive.

The synchronous motors needed the one way clutch effect of the 'fine
hair spring' wrapped around the motor shaft to persuade the motor to run
in the required 'clockwise' direction upon *every* application of mains
supply to eliminate the 50:50 chance of running backwards on start up.

Most Microwave ovens with turntables seem to employ a similar
synchronous motor except for the absence of a 'clockwise persuader clutch
spring mechanism' since it doesn't matter which direction the motor
happens to start turning in. I might be wrong but even these motors might
employ some form of spring assist to get them running since they seem to
alternate direction at each startup with a remarkable consistency ime.

--
Johnny B Good

On 10/09/17 23:26, Archibald Tarquin Blenkinsopp wrote:
If the motor was running you wouldn't need a resistor. If you add
resistance the motor wont move, if it could move on a lower current it
wouldn't be tripping now would it?

That is so pricelsss it ought to be framed and put on a wall.

A man who has absorbed a little physics, but has completely failed to
learn how to think.

Gotta be a dyed in the wool socialist.


--
The theory of Communism may be summed up in one sentence: Abolish all
private property.

Karl Marx