In rec.crafts.metalworking Ignoramus29580 wrote:

http://igor.chudov.com/projects/17.5-Phase-Converter/

I need to do a few extra things, like adding a pushbutton (which I do
not have yet, I bought it on ebay yesterday), some crimpable butt
splices and ring terminals, and preferably adding a second motor
starter instead of a definite purpose contactor. The starter would add
overload protection, which the 10 HP motor has but 7.5 HP motor does
not yet.

i


The leads torqued onto the capacitor terminals backwards is nice. The ground
stud having a plastic cable clamp mixed in with leads is good too. A large
capacitor bank should have bleed resistors as well, it's for your safety.

On Wed, 14 Dec 2005 12:01:49 GMT, Ignoramus19198
wrote:

Well, remember that the capacitors are connected across the windings
of the motors.

Unless you have some wiring removed for maintenance. Then you stick your
paw across the isolated capacitor and zap!

Capacitors should not only have bleed resistors, they should have
individual bleed resistors mounted directly on their terminals, through
their own solder tags, placed below the main terminal. If the studs are
long enough, they should even be nutted down separately so they never
have to be removed.

On Wed, 14 Dec 2005 12:43:47 GMT, Ignoramus19198
wrote:

Hm, if I have wiring removed, then they do not get charged.

There's also a problem known as "dielectric absorption", where a charged
capacitor that's discharged then left disconnected will generate a
charge of its own accord. This has delivered enough of a shock to make a
nun swear (if not more).

You're running your capacitors on AC at a fairly low voltage, so they're
pretty safe, whatever you do. My experience is more with HT DC laser
PSUs at a few kV, where they're real killers if you're not careful.

In rec.crafts.metalworking Andy Dingley wrote:
On Wed, 14 Dec 2005 12:01:49 GMT, Ignoramus19198
wrote:

Well, remember that the capacitors are connected across the windings
of the motors.

Unless you have some wiring removed for maintenance. Then you stick your
paw across the isolated capacitor and zap!

Or if the wire is bolted on counter clockwise so wants to fall off
by itself.


Capacitors should not only have bleed resistors, they should have
individual bleed resistors mounted directly on their terminals, through
their own solder tags, placed below the main terminal. If the studs are
long enough, they should even be nutted down separately so they never
have to be removed.

In rec.crafts.metalworking Ignoramus19198 wrote:
On Wed, 14 Dec 2005 17:04:09 +0000, Andy Dingley wrote:
On Wed, 14 Dec 2005 12:43:47 GMT, Ignoramus19198
wrote:

Hm, if I have wiring removed, then they do not get charged.

There's also a problem known as "dielectric absorption", where a charged
capacitor that's discharged then left disconnected will generate a
charge of its own accord. This has delivered enough of a shock to make a
nun swear (if not more).

But they are never disconnected from motor windings. I made sure of that.

Sure you are, so why not cut off the ground prongs on all your equipment.
Ater all, it will never fail, so there's no need for ground anways.


They are basically directly connected to motor windings, they are
wired into at the contactor/starter outputs along with the motor
leads.

When the motors are running, there is induced voltage between 1-3 and
2-3, so the caps help with keeping it more stable across the range of
3 phase power demand (and possibly prevent phase shift).

When the motors are not running, the caps quickly discharge through
the windings. Any resistor that I would install would have resistance
orders of magnitude less than the windings.

You're running your capacitors on AC at a fairly low voltage, so they're
pretty safe, whatever you do. My experience is more with HT DC laser
PSUs at a few kV, where they're real killers if you're not careful.

Well, 240V AC could charge them at peak voltage of what, about 380
volts? In other words, if the cap is disconnected (which would not
happen in my system), when the charge is at the max, it could be
charged up to 380 volts or there about. That's quite serious at 92 uF
and 184 uF in two paralleled ones.

i

In rec.crafts.metalworking Ignoramus19198 wrote:
On Wed, 14 Dec 2005 07:13:08 +0000 (UTC), Cydrome Leader wrote:
In rec.crafts.metalworking Ignoramus29580 wrote:

http://igor.chudov.com/projects/17.5-Phase-Converter/

I need to do a few extra things, like adding a pushbutton (which I do
not have yet, I bought it on ebay yesterday), some crimpable butt
splices and ring terminals, and preferably adding a second motor
starter instead of a definite purpose contactor. The starter would add
overload protection, which the 10 HP motor has but 7.5 HP motor does
not yet.

i


The leads torqued onto the capacitor terminals backwards is nice.

What do you mean by backwards?

The ground stud having a plastic cable clamp mixed in with leads is
good too.

Good point, although the screw still conducts.

It doesn't matter if the screw conducts if there's a fault current and the
plastic melts off and you lose solid connection to that bolt.



A large capacitor bank should have bleed resistors as
well, it's for your safety.

Well, remember that the capacitors are connected across the windings
of the motors. I did think about it, I think that they discharge very
quickly through the windings. I will double check that though.

This is the wrong mentality to be working on nonsense electrical projects
like this.


i

"Ignoramus19198" wrote in message
.. .

| The leads torqued onto the capacitor terminals backwards is nice.
|
| What do you mean by backwards?

Normally wires are wrapped around the terminal or fastener shank
clockwise. What happens is that the tightening action pulls the wire into
the joint, whereas to wrap it the other way will cause the wire to "squirt
out." In your case you probably didn't see it because you have washers on
both sides of the wire.
BTW, with devices that have any kind of vibration, crimped lugs with
proper insulation grip are the best way to do. The only time you'll see
wire wrapped around a terminal in "legal" applications is for residential
wiring, which is not likely to vibrate. Tying the wires together will also
decrease the stress on the connections, which in your case will get really
ugly when a wire breaks off.
I have a terminal crimper from a seller in Seattle that has really good
crimper sets to suit your need for a good price, considering what you get
for your money. http://stores.ebay.com/EE-INDUSTRIES NFI, just a satisfied
user (They were bought for me for providing automotive services.)

According to Ignoramus8558 :
On Fri, 16 Dec 2005 03:06:45 GMT, carl mciver wrote:

[ ... ]

I have a terminal crimper from a seller in Seattle that has really good
crimper sets to suit your need for a good price, considering what you get
for your money. http://stores.ebay.com/EE-INDUSTRIES NFI, just a satisfied
user (They were bought for me for providing automotive services.)


Thanks. I have a cheapo crimper that actually does a decent job
crimping (meaning that I cannot pull put the wire out). I will redo
those leads in crimped ring terminal form. I also need to crimp on a
few 6 gauge ring terminals, as well. When I do that, I will post new
photos.

One thing to consider is that a crimped terminal should be onto
*stranded* wire, not solid -- at least the ring terminals such as you
already have on the capacitor terminals in some places.

I have seen crimp terminals designed for solid wires -- but
these were not power-handling crimps.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
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--- Black Holes are where God is dividing by zero ---

According to Ignoramus20852 :
On Fri, 16 Dec 2005 20:05:46 +0000, DoN. Nichols wrote:

[ ... ]

One thing to consider is that a crimped terminal should be onto
*stranded* wire, not solid -- at least the ring terminals such as you
already have on the capacitor terminals in some places.

Absolutely, yes, I only use stranded wire for crimping.

Good.

I have seen crimp terminals designed for solid wires -- but
these were not power-handling crimps.

I have been drifting farther and farther away from using solid wire. I
pretty much use it only on breadboard or inside conduits, these
days. The stuff you see on the caps is a remnant of old days and will
be replaced soon.

O.K.

For 6 gauge wire, I will try to use my hydraulic crimper.

Do you have the right dies for #6 wire? IIRC, that would be the
ones with the blue dot (and blue insulation on the terminals). I know
for sure that the yellow is #10 (10-12) ga. Next in the color series is
red, which would be #8, then blue for #6, then yellow again for #4, red
for #2, and that covers the range of your crimper.

Thanks for the tips.

You're welcome,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

According to Ignoramus20852 :
On Fri, 16 Dec 2005 21:18:27 +0000, DoN. Nichols wrote:
According to Ignoramus20852 :
For 6 gauge wire, I will try to use my hydraulic crimper.

Do you have the right dies for #6 wire? IIRC, that would be the
ones with the blue dot (and blue insulation on the terminals). I know
for sure that the yellow is #10 (10-12) ga. Next in the color series is
red, which would be #8, then blue for #6, then yellow again for #4, red
for #2, and that covers the range of your crimper.

The die that I have says that it is for #6.

O.K. And it should have a red dot on each half. Perhaps a
1/10th inch shallow drill hole filled with the paint. (The blue version
is so dark that it is sometimes hard to see.)

I hope that it works, we'll see. I bought some #6 ring terminals, I
hope that they fit the crimper.

Most of them will, though the ones by AMP are the best, of
course.

DoN, do you think that there is value of soldering after a proper
crimp (that does not pull out despite string tugging)?

*No*! If it pulls out, it was not crimped hard enough, or was
the wrong size of wire for the terminal and dies.

One major threat if you flow solder into it is that it will wick
on through and into the insulation a little bit, turning your
multi-strand flexible wire into a solid wire -- much more likely to fail
during vibration.

For soldered connections in aerospace applications, where
vibration is a given, there are anti-wicking tweezers to prevent this
from happening while you solder the wire to a terminal.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

According to Ignoramus20852 :
DoN, sorry, forgot to say Thank You.

You're welcome,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In rec.crafts.metalworking Ignoramus8558 wrote:
On Fri, 16 Dec 2005 02:23:32 +0000 (UTC), Cydrome Leader wrote:
In rec.crafts.metalworking Ignoramus19198 wrote:
On Wed, 14 Dec 2005 07:13:08 +0000 (UTC), Cydrome Leader wrote:
In rec.crafts.metalworking Ignoramus29580 wrote:

http://igor.chudov.com/projects/17.5-Phase-Converter/

I need to do a few extra things, like adding a pushbutton (which I do
not have yet, I bought it on ebay yesterday), some crimpable butt
splices and ring terminals, and preferably adding a second motor
starter instead of a definite purpose contactor. The starter would add
overload protection, which the 10 HP motor has but 7.5 HP motor does
not yet.

i


The leads torqued onto the capacitor terminals backwards is nice.

What do you mean by backwards?

The ground stud having a plastic cable clamp mixed in with leads is
good too.

Good point, although the screw still conducts.

It doesn't matter if the screw conducts if there's a fault current and the
plastic melts off and you lose solid connection to that bolt.

Okay, I buy it. What value (ohms and watts) would you suggest?

Tell me the size of the caps in uF and the voltage you measure across them
and I'll come up with some values for you.

In rec.crafts.metalworking Ignoramus22094 wrote:

Okay, I buy it. What value (ohms and watts) would you suggest?

Tell me the size of the caps in uF and the voltage you measure across them
and I'll come up with some values for you.

240 VAC, each cap is 94 uF.


1/2 watt 150KOhm will drop the residual voltage to about 15% of 240 in 30
seconds. That's two RC time constants of 150kOhm x 94uF. That gives us a
peak of about 240*1.4 * 0.15 (50 volts) after 28 or so seconds, assuming
the caps were charged just before the peak of the 240 volt cycle.

since power is (I^2)/R, we get 240 * 240 or 57600/150000 which is 0.384
watts.

You may need to adjust these for variations in line voltage and capacitor
tolerance. The 30 seconds to a "safe" voltage I made is arbitrary. 30
seconds seems like a safe amount of time to shut of a project, unplug it
and start playing with the insides.

Just for fun, utility company power factor caps are designed to discharge
to 50 volts or less after 5 minutes of disconnect.

In rec.crafts.metalworking Ignoramus21405 wrote:
On Tue, 27 Dec 2005 01:53:33 +0000 (UTC), Cydrome Leader wrote:
In rec.crafts.metalworking Ignoramus22094 wrote:

Okay, I buy it. What value (ohms and watts) would you suggest?

Tell me the size of the caps in uF and the voltage you measure across them
and I'll come up with some values for you.

240 VAC, each cap is 94 uF.


1/2 watt 150KOhm will drop the residual voltage to about 15% of 240 in 30
seconds. That's two RC time constants of 150kOhm x 94uF. That gives us a
peak of about 240*1.4 * 0.15 (50 volts) after 28 or so seconds, assuming
the caps were charged just before the peak of the 240 volt cycle.

since power is (I^2)/R, we get 240 * 240 or 57600/150000 which is 0.384
watts.

You may need to adjust these for variations in line voltage and capacitor
tolerance. The 30 seconds to a "safe" voltage I made is arbitrary. 30
seconds seems like a safe amount of time to shut of a project, unplug it
and start playing with the insides.

Just for fun, utility company power factor caps are designed to discharge
to 50 volts or less after 5 minutes of disconnect.

Thank you CL. I will follow your advice, maybe will use 100 k instead
of 200, but I will do it.

Although I didn't mention it, this is the value of resistor per capacitor.
While it's true about 400uF at a few hundred volts probably won't kill
you, it is on par with the voltage and energy of a medium sized on-camera
camera flash. It's quite unpleasant to touch. The main concern is you
jump/jerk/fall into something more dangerous.

In rec.crafts.metalworking Ignoramus6309 wrote:
On Thu, 29 Dec 2005 08:52:54 +0000 (UTC), Cydrome Leader wrote:
In rec.crafts.metalworking Ignoramus21405 wrote:
On Tue, 27 Dec 2005 01:53:33 +0000 (UTC), Cydrome Leader wrote:
In rec.crafts.metalworking Ignoramus22094 wrote:

Okay, I buy it. What value (ohms and watts) would you suggest?

Tell me the size of the caps in uF and the voltage you measure across them
and I'll come up with some values for you.

240 VAC, each cap is 94 uF.


1/2 watt 150KOhm will drop the residual voltage to about 15% of 240 in 30
seconds. That's two RC time constants of 150kOhm x 94uF. That gives us a
peak of about 240*1.4 * 0.15 (50 volts) after 28 or so seconds, assuming
the caps were charged just before the peak of the 240 volt cycle.

since power is (I^2)/R, we get 240 * 240 or 57600/150000 which is 0.384
watts.

You may need to adjust these for variations in line voltage and capacitor
tolerance. The 30 seconds to a "safe" voltage I made is arbitrary. 30
seconds seems like a safe amount of time to shut of a project, unplug it
and start playing with the insides.

Just for fun, utility company power factor caps are designed to discharge
to 50 volts or less after 5 minutes of disconnect.

Thank you CL. I will follow your advice, maybe will use 100 k instead
of 200, but I will do it.

Although I didn't mention it, this is the value of resistor per capacitor.

Yes, that's how I understood it. One resistor per capacitor, very
close to terminals.

In my case, it is more of a feel good, neatness issue, but worth doing
"just in case".

You don't conduct electricity?

While it's true about 400uF at a few hundred volts probably won't kill
you, it is on par with the voltage and energy of a medium sized on-camera
camera flash. It's quite unpleasant to touch. The main concern is you
jump/jerk/fall into something more dangerous.

I tried shorting one of those caps with a screwdriver. The sound was
like a crack of a .22.

i