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Default The devil made me do it

Spent about 6 hours finding and wiring a reversing relay for my 8 Amp, 58/105 DC
volt, shunt wound GE motor. Worked like an absolute charm but I decided to see if it
could stand being reversed without stopping. The smoke came out!

The field's still getting the full 58 volts but the armature voltage (sadly) is now
only
working between about 19 and 36 volts. (no longer up to 105 V)

Probably asking the impossible but can anyone offer any suggestions as to the
probable cause of failure. And might it be possible to strip out the speed control
circuit (if it is screwed) and run the motor at its full rated speed using current
directly from the full wave rectifier?

Had planned to to run this motor on a small lathe.

Thanks T

(Spam address)

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Default The devil made me do it

On Tue, 11 Sep 2007 13:48:55 -0400, Ted Samuels
wrote:

Spent about 6 hours finding and wiring a reversing relay for my 8 Amp, 58/105 DC
volt, shunt wound GE motor. Worked like an absolute charm but I decided to see if it
could stand being reversed without stopping. The smoke came out!

The field's still getting the full 58 volts but the armature voltage (sadly) is now
only
working between about 19 and 36 volts. (no longer up to 105 V)

Probably asking the impossible but can anyone offer any suggestions as to the
probable cause of failure. And might it be possible to strip out the speed control
circuit (if it is screwed) and run the motor at its full rated speed using current
directly from the full wave rectifier?

Had planned to to run this motor on a small lathe.

Thanks T

(Spam address)



You _cannot_ plug reverse a DC motor. When the motor is running it acts as a
generator in opposition to the supply voltage. The current through the
armature is due to the difference between the supply voltage and the generated
voltage, all divided by the armature resistance.

When you reversed the supply, that reverse voltage due to the rotation of the
motor was added to the supply instead of being subtracted from it

So you probably went from about one volt, or less, driving the current through
the armature to 115 volts... Exit magic smoke stage left.

If you need to reverse the motor rapidly, you need to think in terms of a
forward-stop-reverse switch. the stop position can have a biggish resistor
shorting the armature. The resistance can be sized to allow about twice the
rated current at the rated voltage. The motor should be stopped before
reversing. Alternatively, It is possible to buy PTC based soft starters that
might be used to limit the armature current with this sort of treatment, but
those might slow down the stopping and starting process. YMMV

If the speed control circuit is designed smart enough, it can cope with
reversing the motor by absorbing the braking power itself and controlling the
armature current so that you change speed at the fastest rate that the motor
can handle (e.g. running at maximum torque decelerating and accelerating). But
it sounds like your circuit isn't doing that :-(


HTH

Mark Rand
RTFM
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Default The devil made me do it

Mark Rand wrote:
On Tue, 11 Sep 2007 13:48:55 -0400, Ted Samuels wrote:

Spent about 6 hours finding and wiring a reversing relay for my 8 Amp, 58/105 DC
volt, shunt wound GE motor. Worked like an absolute charm but I decided to see
if it could stand being reversed without stopping. The smoke came out!

The field's still getting the full 58 volts but the armature voltage (sadly)
is now only working between about 19 and 36 volts. (no longer up to 105 V)

Probably asking the impossible but can anyone offer any suggestions as to the
probable cause of failure. And might it be possible to strip out the speed
control circuit (if it is screwed) and run the motor at its full rated speed
using current directly from the full wave rectifier?

Had planned to to run this motor on a small lathe.

Thanks T

(Spam address)



You _cannot_ plug reverse a DC motor. When the motor is running it acts as a
generator in opposition to the supply voltage. The current through the armature is
due to the difference between the supply voltage and the generated voltage, all
divided by the armature resistance.

When you reversed the supply, that reverse voltage due to the rotation of the
motor was added to the supply instead of being subtracted from it

So you probably went from about one volt, or less, driving the current through the
armature to 115 volts... Exit magic smoke stage left.

If you need to reverse the motor rapidly, you need to think in terms of a
forward-stop-reverse switch. the stop position can have a biggish resistor
shorting the armature. The resistance can be sized to allow about twice the rated
current at the rated voltage. The motor should be stopped before reversing.
Alternatively, It is possible to buy PTC based soft starters that might be used to
limit the armature current with this sort of treatment, but those might slow down
the stopping and starting process. YMMV

If the speed control circuit is designed smart enough, it can cope with reversing
the motor by absorbing the braking power itself and controlling the armature
current so that you change speed at the fastest rate that the motor can handle
(e.g. running at maximum torque decelerating and accelerating). But it sounds like
your circuit isn't doing that :-(


HTH

Mark Rand RTFM


Thanks Mark

RTFM! Sure, good advise, if I had one. The motor and control were something that was
in a lot that I bid on a dozen years ago and to give you an idea of it's age, there
was a
penned in note mentioning a repair done in 71.

I was hoping to get a steer in the direction of what's most likely damaged . In any case
I gave myself a good lesson on reversing.

Thanks again
T


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Default The devil made me do it

Mark Rand wrote:

On Tue, 11 Sep 2007 13:48:55 -0400, Ted Samuels
wrote:

Spent about 6 hours finding and wiring a reversing relay for my 8 Amp, 58/105 DC
volt, shunt wound GE motor. Worked like an absolute charm but I decided to see if it
could stand being reversed without stopping. The smoke came out!

The field's still getting the full 58 volts but the armature voltage (sadly) is now
only
working between about 19 and 36 volts. (no longer up to 105 V)

Probably asking the impossible but can anyone offer any suggestions as to the
probable cause of failure. And might it be possible to strip out the speed control
circuit (if it is screwed) and run the motor at its full rated speed using current
directly from the full wave rectifier?

Had planned to to run this motor on a small lathe.

Thanks T

(Spam address)


You _cannot_ plug reverse a DC motor. When the motor is running it acts as a
generator in opposition to the supply voltage. The current through the
armature is due to the difference between the supply voltage and the generated
voltage, all divided by the armature resistance.

When you reversed the supply, that reverse voltage due to the rotation of the
motor was added to the supply instead of being subtracted from it

So you probably went from about one volt, or less, driving the current through
the armature to 115 volts... Exit magic smoke stage left.

If you need to reverse the motor rapidly, you need to think in terms of a
forward-stop-reverse switch. the stop position can have a biggish resistor
shorting the armature. The resistance can be sized to allow about twice the
rated current at the rated voltage. The motor should be stopped before
reversing. Alternatively, It is possible to buy PTC based soft starters that
might be used to limit the armature current with this sort of treatment, but
those might slow down the stopping and starting process. YMMV

If the speed control circuit is designed smart enough, it can cope with
reversing the motor by absorbing the braking power itself and controlling the
armature current so that you change speed at the fastest rate that the motor
can handle (e.g. running at maximum torque decelerating and accelerating). But
it sounds like your circuit isn't doing that :-(

HTH

Mark Rand
RTFM


The spindle VFD's on the DC motor driven lathes will decelerate stop and
reverse in a minimum amount of time if they are set up right. You can
go directly from forward to reverse with no problem. If the
deceleration times are not set up right you start blowing fuses.

John
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Default The devil made me do it

if there is electronics, it's most assuredly damaged - power the motor
separately from the electronics and see if it works, if yes, then you at
least know where to look - a modern DC motor control is not too expensive
though and there are a lot on ebay, otherwise look at Minarik.com they make
nice ones



I was hoping to get a steer in the direction of what's most likely damaged
. In any case
I gave myself a good lesson on reversing.

Thanks again
T





--
Posted via a free Usenet account from http://www.teranews.com



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Default The devil made me do it

William Noble wrote:
if there is electronics, it's most assuredly damaged - power the motor separately
from the electronics and see if it works, if yes, then you at least know where to
look - a modern DC motor control is not too expensive though and there are a lot
on ebay, otherwise look at Minarik.com they make nice ones


I was hoping to get a steer in the direction of what's most likely damaged . In
any case I gave myself a good lesson on reversing.

Thanks again T


Thanks William (Bill)

Yes, I expect my adventure will cost me the price of a new controller. Kind of a shame.
It was a nice setup. I suppose I could still use it to provide the field current and
a variac with a rectifier for the current to the armature. I enjoy tinkering.

The lathe is already powered so there is no urgency. I just thought the reverse and
variable speed of the DC motor would have been a nice touch.

Thanks for the good advise.
T
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Default The devil made me do it

FWIW I've had no problems "plug reversing" (actually it was a classic DPDT
switch wired as reversing switch) PM DC motors, Both fractional gear motors
I've used for powerfeeds and a good sized 90VDC I've used for spindle
motors,
but my speed control was not electronic, but a big assed Variac and diodes
from hell. I did it all the time on the power feeds running at about half
speed and ocassionaly on the spindle motor usually running pretty slow when
threading, (made threading metric to a shoulder a snap. -) A big caviet
here is that doing this to PM DC motors WILL demag them over time... shrug
....


I suspect that the issue here is that reversed voltage blew the SCR's,
TRIACS or DIODES in the speed control.

Yes you should be able to drive the armature directly from some from of
rectifier, but remember if you use a full wave bridge, yer gonna be hitting
that thing with around 150VDC.. (the 120 is an RMS value, 120 x 1.4 is about
170 peek)

You might consider just a half wave... I know those, 50/100's are "growlers"
any way so....

Also if you are still going to "hot reverse" this motor you better get 400V
Diodes since you'll be adding your generated voltage to the 170 when you hit
the reverse switch.

--.- Dave


"Mark Rand" wrote in message
...
On Tue, 11 Sep 2007 13:48:55 -0400, Ted Samuels
wrote:

Spent about 6 hours finding and wiring a reversing relay for my 8 Amp,
58/105 DC
volt, shunt wound GE motor. Worked like an absolute charm but I decided to
see if it
could stand being reversed without stopping. The smoke came out!

The field's still getting the full 58 volts but the armature voltage
(sadly) is now
only
working between about 19 and 36 volts. (no longer up to 105 V)

Probably asking the impossible but can anyone offer any suggestions as to
the
probable cause of failure. And might it be possible to strip out the speed
control
circuit (if it is screwed) and run the motor at its full rated speed using
current
directly from the full wave rectifier?

Had planned to to run this motor on a small lathe.

Thanks T

(Spam address)



You _cannot_ plug reverse a DC motor. When the motor is running it acts as
a
generator in opposition to the supply voltage. The current through the
armature is due to the difference between the supply voltage and the
generated
voltage, all divided by the armature resistance.

When you reversed the supply, that reverse voltage due to the rotation of
the
motor was added to the supply instead of being subtracted from it

So you probably went from about one volt, or less, driving the current
through
the armature to 115 volts... Exit magic smoke stage left.

If you need to reverse the motor rapidly, you need to think in terms of a
forward-stop-reverse switch. the stop position can have a biggish resistor
shorting the armature. The resistance can be sized to allow about twice
the
rated current at the rated voltage. The motor should be stopped before
reversing. Alternatively, It is possible to buy PTC based soft starters
that
might be used to limit the armature current with this sort of treatment,
but
those might slow down the stopping and starting process. YMMV

If the speed control circuit is designed smart enough, it can cope with
reversing the motor by absorbing the braking power itself and controlling
the
armature current so that you change speed at the fastest rate that the
motor
can handle (e.g. running at maximum torque decelerating and accelerating).
But
it sounds like your circuit isn't doing that :-(


HTH

Mark Rand
RTFM



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Default The devil made me do it

On Sep 11, 1:48 pm, Ted Samuels wrote:
Spent about 6 hours finding and wiring a reversing relay for my 8 Amp, 58/105 DC
volt, shunt wound GE motor. Worked like an absolute charm but I decided to see if it
could stand being reversed without stopping. The smoke came out!

The field's still getting the full 58 volts but the armature voltage (sadly) is now
only
working between about 19 and 36 volts. (no longer up to 105 V)

Probably asking the impossible but can anyone offer any suggestions as to the
probable cause of failure. And might it be possible to strip out the speed control
circuit (if it is screwed) and run the motor at its full rated speed using current
directly from the full wave rectifier?

Had planned to to run this motor on a small lathe.

Thanks T

(Spam address)


All I know from my own experience is plug stop reversed motors fail
far far sooner than ones that come to a full stop before reversing, At
least this is the case on saw chain and mower blade grinders.

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Posts: 790
Default The devil made me do it

if you want to fix the electronics, start by providing some information -
like what is it, is there any visible damage, and a photo. As others
pointed out, it's most likely diodes and SCRs and transistors that are
damaged, the older drives are easy to fix, just find all the bad parts and
replace them - newer ones have surface mounted parts and custom VLSI and are
much harder to work on. SCRs cost a dollar or two each, you can look up by
part number what the specs are and buy a modern number.

so, have you actually tested the motor? a car battery provides enough
voltage to run a 100 V motor, just energize both the field and armature and
see if it turns
"Ted Samuels" wrote in message
...
William Noble wrote:
if there is electronics, it's most assuredly damaged - power the motor
separately
from the electronics and see if it works, if yes, then you at least know
where to
look - a modern DC motor control is not too expensive though and there
are a lot
on ebay, otherwise look at Minarik.com they make nice ones


I was hoping to get a steer in the direction of what's most likely
damaged . In
any case I gave myself a good lesson on reversing.

Thanks again T


Thanks William (Bill)

Yes, I expect my adventure will cost me the price of a new controller.
Kind of a shame.
It was a nice setup. I suppose I could still use it to provide the field
current and
a variac with a rectifier for the current to the armature. I enjoy
tinkering.

The lathe is already powered so there is no urgency. I just thought the
reverse and
variable speed of the DC motor would have been a nice touch.

Thanks for the good advise.
T




--
Posted via a free Usenet account from http://www.teranews.com

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Default The devil made me do it

Dave August wrote:
FWIW I've had no problems "plug reversing" (actually it was a classic DPDT
switch wired as reversing switch) PM DC motors, Both fractional gear motors
I've used for powerfeeds and a good sized 90VDC I've used for spindle
motors,
but my speed control was not electronic, but a big assed Variac and diodes
from hell. I did it all the time on the power feeds running at about half
speed and ocassionaly on the spindle motor usually running pretty slow when
threading, (made threading metric to a shoulder a snap. -) A big caviet
here is that doing this to PM DC motors WILL demag them over time... shrug
...


I suspect that the issue here is that reversed voltage blew the SCR's,
TRIACS or DIODES in the speed control.

Yes you should be able to drive the armature directly from some from of
rectifier, but remember if you use a full wave bridge, yer gonna be hitting
that thing with around 150VDC.. (the 120 is an RMS value, 120 x 1.4 is about
170 peek)

You might consider just a half wave... I know those, 50/100's are "growlers"
any way so....

Also if you are still going to "hot reverse" this motor you better get 400V
Diodes since you'll be adding your generated voltage to the 170 when you hit
the reverse switch.

--.- Dave


Yes! Thanks Dave!

I'm going to cut my losses on this and go for a set up like yours. I have a half dozen
90 volt pm dc drives and three 10 amp variacs and possibly one more if I could ever
find it. Got to find some "diodes from hell" and I'll be all set.

I don't understand the math involved in calculating ("if you use a full wave bridge, yer
gonna be hitting that thing with around 150VDC.. (the 120 is an RMS value, 120 x
1.4 is about
170 peek) )" but I think you are saying that if I pit 120 ACV across the Variac
and out through a full wave rectifier, at full rotation of the variac the output DC
voltage will be 150 DCV and peek at 170 V

This being the case,, I could limit the rotation of to variac and utilize the 20
volt tap on these variacs.

Better run, have to respond to a couple of other guys that were good enough to lend a
hand.

Thanks
T






"Mark Rand" wrote in message
...
On Tue, 11 Sep 2007 13:48:55 -0400, Ted Samuels
wrote:

Spent about 6 hours finding and wiring a reversing relay for my 8 Amp,
58/105 DC
volt, shunt wound GE motor. Worked like an absolute charm but I decided to
see if it
could stand being reversed without stopping. The smoke came out!

The field's still getting the full 58 volts but the armature voltage
(sadly) is now
only
working between about 19 and 36 volts. (no longer up to 105 V)

Probably asking the impossible but can anyone offer any suggestions as to
the
probable cause of failure. And might it be possible to strip out the speed
control
circuit (if it is screwed) and run the motor at its full rated speed using
current
directly from the full wave rectifier?

Had planned to to run this motor on a small lathe.

Thanks T

(Spam address)


You _cannot_ plug reverse a DC motor. When the motor is running it acts as
a
generator in opposition to the supply voltage. The current through the
armature is due to the difference between the supply voltage and the
generated
voltage, all divided by the armature resistance.

When you reversed the supply, that reverse voltage due to the rotation of
the
motor was added to the supply instead of being subtracted from it

So you probably went from about one volt, or less, driving the current
through
the armature to 115 volts... Exit magic smoke stage left.

If you need to reverse the motor rapidly, you need to think in terms of a
forward-stop-reverse switch. the stop position can have a biggish resistor
shorting the armature. The resistance can be sized to allow about twice
the
rated current at the rated voltage. The motor should be stopped before
reversing. Alternatively, It is possible to buy PTC based soft starters
that
might be used to limit the armature current with this sort of treatment,
but
those might slow down the stopping and starting process. YMMV

If the speed control circuit is designed smart enough, it can cope with
reversing the motor by absorbing the braking power itself and controlling
the
armature current so that you change speed at the fastest rate that the
motor
can handle (e.g. running at maximum torque decelerating and accelerating).
But
it sounds like your circuit isn't doing that :-(


HTH

Mark Rand
RTFM





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Default The devil made me do it

beecrofter wrote:
On Sep 11, 1:48 pm, Ted Samuels wrote:
Spent about 6 hours finding and wiring a reversing relay for my 8 Amp, 58/105 DC
volt, shunt wound GE motor. Worked like an absolute charm but I decided to see if it
could stand being reversed without stopping. The smoke came out!

The field's still getting the full 58 volts but the armature voltage (sadly) is now
only
working between about 19 and 36 volts. (no longer up to 105 V)

Probably asking the impossible but can anyone offer any suggestions as to the
probable cause of failure. And might it be possible to strip out the speed control
circuit (if it is screwed) and run the motor at its full rated speed using current
directly from the full wave rectifier?

Had planned to to run this motor on a small lathe.

Thanks T

(Spam address)


All I know from my own experience is plug stop reversed motors fail
far far sooner than ones that come to a full stop before reversing, At
least this is the case on saw chain and mower blade grinders.


I never should have done it. I had the damn thing working perfectly.
I slowed the motor to a crawl and hit my newly minted reversing
relay switch. I half way knew something would go wrong but like I said
" the devil mad me do it."

Well now I know for sure what would happen. Better find out
before I went to the bother of replacing the existing motor.

Got to find some good in what I did. Perhaps it will save some one
else from the same fate.

Besides, I am retired and I like messing around.

Thanks
T

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Default The devil made me do it

As I mentioned earlier, I think I'll cut my losses and scrap the controller. BTW
the controller will still drive the motor in forward and reverse but the armature
is only getting about 19 volts at minimum speed and 36 volts at a slightly higher
RPM. Perhaps 150 RPM. In addition to that the "ON" breakers are now chattering
and I have to hold the "ON" switch for a second or so to get it to latch.

Better scoot now. Thanks Bill


William Noble wrote:
if you want to fix the electronics, start by providing some information -
like what is it, is there any visible damage, and a photo. As others
pointed out, it's most likely diodes and SCRs and transistors that are
damaged, the older drives are easy to fix, just find all the bad parts and
replace them - newer ones have surface mounted parts and custom VLSI and are
much harder to work on. SCRs cost a dollar or two each, you can look up by
part number what the specs are and buy a modern number.

so, have you actually tested the motor? a car battery provides enough
voltage to run a 100 V motor, just energize both the field and armature and
see if it turns
"Ted Samuels" wrote in message
...
William Noble wrote:
if there is electronics, it's most assuredly damaged - power the motor
separately
from the electronics and see if it works, if yes, then you at least know
where to
look - a modern DC motor control is not too expensive though and there
are a lot
on ebay, otherwise look at Minarik.com they make nice ones


I was hoping to get a steer in the direction of what's most likely
damaged . In
any case I gave myself a good lesson on reversing.

Thanks again T

Thanks William (Bill)

Yes, I expect my adventure will cost me the price of a new controller.
Kind of a shame.
It was a nice setup. I suppose I could still use it to provide the field
current and
a variac with a rectifier for the current to the armature. I enjoy
tinkering.

The lathe is already powered so there is no urgency. I just thought the
reverse and
variable speed of the DC motor would have been a nice touch.

Thanks for the good advise.
T




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Default The devil made me do it

ted - why don't you try and fix the controller? it sounds like it has a bad
diode or two in a full wave bridge, or a smoked SCR -
1. do you have a schematic? if yes, several of us could suggest probable
parts to check/change
2. if no schematic, can you tell an SCR from a resistor? if yes, just
change the SCRs and diodes, you have about a 60% chance of getting it
working that way, if no, maybe a photo onto binaries? Can you solder? if
no, better not mess with it, but if yes, then you can probably fix it



"Ted Samuels" wrote in message
...
beecrofter wrote:

Well now I know for sure what would happen. Better find out
before I went to the bother of replacing the existing motor.

Got to find some good in what I did. Perhaps it will save some one
else from the same fate.

Besides, I am retired and I like messing around.

Thanks
T




--
Posted via a free Usenet account from http://www.teranews.com

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Default The devil made me do it

William Noble wrote:
ted - why don't you try and fix the controller?


I'll see if I can read the part numbers from the devices in the heat sink and look
them up on google if I can.

Left to see what was in the controller.

Yes there are a pair of 2N5165, pressed into the sink, they are about 1/2" dia with
two terminals each
and two 1/2" dia A448 single terminal (diodes??) pressed into a second sink.

it sounds like it has a bad
diode or two in a full wave bridge, or a smoked SCR -
1. do you have a schematic? if yes, several of us could suggest probable
parts to check/change

I can only wish! (I looked up the only number printed on the case and it turned out
to be the part no of the fuse

2. if no schematic, can you tell an SCR from a resistor? if yes, just
change the SCRs and diodes, you have about a 60% chance of getting it
working that way, if no, maybe a photo onto binaries? Can you solder? if
no, better not mess with it, but if yes, then you can probably fix it


Yes I am a bit familiar with diodes resistors and caps but I would be hard pressed to
identify an SCR. I assume it would pass for a diode with an extra connection for a
gate (if thats the right name, IE to control the flow through the SCR)

Question is do they have to be removed to be tested or do you have to pull them to test?

Better run got fish to fry

T



"Ted Samuels" wrote in message
...
beecrofter wrote:

Well now I know for sure what would happen. Better find out
before I went to the bother of replacing the existing motor.

Got to find some good in what I did. Perhaps it will save some one
else from the same fate.

Besides, I am retired and I like messing around.

Thanks
T




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Default The devil made me do it

Ted Samuels wrote:
William Noble wrote:
ted - why don't you try and fix the controller?


I'll see if I can read the part numbers from the devices in the heat
sink and look them up on google if I can.

Left to see what was in the controller.

Yes there are a pair of 2N5165, pressed into the sink, they are about
1/2" dia with two terminals each
and two 1/2" dia A448 single terminal (diodes??) pressed into a second
sink.


A448 should read A44B Eyes are getting old!







it sounds like it has a bad
diode or two in a full wave bridge, or a smoked SCR -
1. do you have a schematic? if yes, several of us could suggest
probable parts to check/change

I can only wish! (I looked up the only number printed on the case and it
turned out to be the part no of the fuse

2. if no schematic, can you tell an SCR from a resistor? if yes,
just change the SCRs and diodes, you have about a 60% chance of
getting it working that way, if no, maybe a photo onto binaries? Can
you solder? if no, better not mess with it, but if yes, then you can
probably fix it


Yes I am a bit familiar with diodes resistors and caps but I would be
hard pressed to identify an SCR. I assume it would pass for a diode with
an extra connection for a gate (if thats the right name, IE to control
the flow through the SCR)

Question is do they have to be removed to be tested or do you have to
pull them to test?

Better run got fish to fry

T



"Ted Samuels" wrote in message
...
beecrofter wrote:

Well now I know for sure what would happen. Better find out
before I went to the bother of replacing the existing motor.

Got to find some good in what I did. Perhaps it will save some one
else from the same fate.

Besides, I am retired and I like messing around.

Thanks
T






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2N5165 is an SCR (google is your friend) - I will bet you that one of them
is destroyed. the summary description is:

Silicon controlled rectifier. Reverse blocking triode thyristor. Peak
repetitive forward or reverse blocking voltage 200 V. in 2-pin 310-02
package. Operational temperature range from -40°C to 100°C.

an SCR in a more modern package will be cheaper, but usually these parts are
quite inexpensive. See if you can find a source and get a price - easiest
to just change both if they are just a couple of $$. The other two things
are diodes - you can use any stud mounted diode with a reasonable PIV (say
200 to 400v) and a current of at least the max current you will draw through
the controller.

What is connected to the leads on the SCRs? the drive to one SCR may be
damaged also

"Ted Samuels" wrote in message
...
Ted Samuels wrote:
William Noble wrote:
ted - why don't you try and fix the controller?


I'll see if I can read the part numbers from the devices in the heat sink
and look them up on google if I can.

Left to see what was in the controller.

Yes there are a pair of 2N5165, pressed into the sink, they are about
1/2" dia with two terminals each
and two 1/2" dia A448 single terminal (diodes??) pressed into a second
sink.


A448 should read A44B Eyes are getting old!







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William Noble wrote:
2N5165 is an SCR (google is your friend) - I will bet you that one of them
is destroyed. the summary description is:

Silicon controlled rectifier. Reverse blocking triode thyristor. Peak
repetitive forward or reverse blocking voltage 200 V. in 2-pin 310-02
package. Operational temperature range from -40°C to 100°C.

an SCR in a more modern package will be cheaper, but usually these parts are
quite inexpensive. See if you can find a source and get a price - easiest
to just change both if they are just a couple of $$. The other two things
are diodes - you can use any stud mounted diode with a reasonable PIV (say
200 to 400v) and a current of at least the max current you will draw through
the controller.

What is connected to the leads on the SCRs? the drive to one SCR may be
damaged also

Yes there are a pair of 2N5165, pressed into the sink, they are about
1/2" dia with two terminals each
and two 1/2" dia A448 single terminal (diodes??) pressed into a second
sink.

A448 should read A44B Eyes are getting old!



Is there any way to test the operation of the SRC without removal ?
I read up on how to test and I think I could manage to do the test

Thanks for the offer to source but I have found them , to be special
ordered through a local guy at $9.95 ea and $5.78 ea for the diodes.

The dealer's a good guy,, (says he will special order any time.(without
having to go across town and make a deposit)

Better run
T
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Ted Samuels wrote:
William Noble wrote:
2N5165 is an SCR (google is your friend) - I will bet you that one of them is
destroyed. the summary description is:

Silicon controlled rectifier. Reverse blocking triode thyristor. Peak repetitive
forward or reverse blocking voltage 200 V. in 2-pin 310-02 package. Operational
temperature range from -40°C to 100°C.

an SCR in a more modern package will be cheaper, but usually these parts are
quite inexpensive. See if you can find a source and get a price - easiest to
just change both if they are just a couple of $$. The other two things are
diodes - you can use any stud mounted diode with a reasonable PIV (say 200 to
400v) and a current of at least the max current you will draw through the
controller.

What is connected to the leads on the SCRs? the drive to one SCR may be damaged
also

Yes there are a pair of 2N5165, pressed into the sink, they are about 1/2"
dia with two terminals each and two 1/2" dia A448 single terminal
(diodes??) pressed into a second sink.
A448 should read A44B Eyes are getting old!



Is there any way to test the operation of the SRC without removal ? I read up on
how to test and I think I could manage to do the test

Thanks for the offer to source but I have found them , to be special ordered
through a local guy at $9.95 ea and $5.78 ea for the diodes.

The dealer's a good guy,, (says he will special order any time.(without having to
go across town and make a deposit)

Better run T

I de-soldered the four components and tested them all. I followed the test guide for
the SCRs and wasn't totally sure they were shot until I tested an SCR from an old
power supply. It behaved exactly as my instructions said it should. The two SCRs in
the controller acted nothing like the good one. So I am confident that I am on the
right track.

Had a little fun pressing the components out of the heat sinks, but I have a set of
12 LC Vise Grips which have the reach to get in between the heat sinks and with the
aid of a small pin taped to one jaw and a socket on the top end of the component the
all pressed out slick as you could wish for. The internet instruction suggested I
pry them out with a flat tip screw driver.

When pigs fly!!!

Will be 3 to 4 weeks to get the SCRs.

Gotta run

T

Change the . to a 1 to contact me direct.

















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Default The devil made me do it

now that you know the SCRs are bad (were the diodes also bad?) I'd suggest
you replace them with parts having a different form factor that is more
common - stud mounted diodes are common (I have some used ones for sale
soemwhere on my web page, but they are cheap), and most low power SCRs
nowadays mount via a single screw through a flange - your electronics supply
place can help you select modern parts that are electrically equivalent to
your old dead ones.

Check whatever was connected to the gate of the SCRs - it may have been hurt
also - typically SCRs fail short circuit, then blow an internal wire and go
open circuit (if they don't just explode their case)


T
I de-soldered the four components and tested them all. I followed the test
guide for
the SCRs and wasn't totally sure they were shot until I tested an SCR from
an old
power supply. It behaved exactly as my instructions said it should. The
two SCRs in
the controller acted nothing like the good one. So I am confident that I
am on the
right track.

Had a little fun pressing the components out of the heat sinks, but I have
a set of
12 LC Vise Grips which have the reach to get in between the heat sinks and
with the
aid of a small pin taped to one jaw and a socket on the top end of the
component the
all pressed out slick as you could wish for. The internet instruction
suggested I
pry them out with a flat tip screw driver.

When pigs fly!!!

Will be 3 to 4 weeks to get the SCRs.

Gotta run




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Default The devil made me do it

William Noble wrote:
now that you know the SCRs are bad (were the diodes also bad?) I'd suggest
you replace them with parts having a different form factor that is more
common - stud mounted diodes are common (I have some used ones for sale
soemwhere on my web page, but they are cheap), and most low power SCRs
nowadays mount via a single screw through a flange - your electronics supply
place can help you select modern parts that are electrically equivalent to
your old dead ones.


The diodes were dead short in on direction and both about 200 K ohms in the opposite.
That seemed OK to me but all the other diodes I had were in the 900 K ohm range so I
went ahead and ordered replacements


Check whatever was connected to the gate of the SCRs - it may have been hurt
also - typically SCRs fail short circuit, then blow an internal wire and go
open circuit (if they don't just explode their case)


Well I'll just have to see if replacing th four components does the trick or not.

Got quite a surprise today. Tried running one of my 60 volt DC motors (I thought they
were 90 volt motors) with a variac and my setup tripped the breaker in my power bar.
Checked and rechecked the circuits from the variac through the bridge and motor and
everything seemed logical. tried it again and again it tripped (not very smart
really). Then I happened to notice in small print on the very front of the variac
"360 cycles per minute" 6 HZ

Live and learn!

Thanks again
T


T
I de-soldered the four components and tested them all. I followed the test
guide for
the SCRs and wasn't totally sure they were shot until I tested an SCR from
an old
power supply. It behaved exactly as my instructions said it should. The
two SCRs in
the controller acted nothing like the good one. So I am confident that I
am on the
right track.

Had a little fun pressing the components out of the heat sinks, but I have
a set of
12 LC Vise Grips which have the reach to get in between the heat sinks and
with the
aid of a small pin taped to one jaw and a socket on the top end of the
component the
all pressed out slick as you could wish for. The internet instruction
suggested I
pry them out with a flat tip screw driver.

When pigs fly!!!

Will be 3 to 4 weeks to get the SCRs.

Gotta run






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Default The devil made me do it

According to William Noble :
now that you know the SCRs are bad (were the diodes also bad?) I'd suggest
you replace them with parts having a different form factor that is more
common - stud mounted diodes are common (I have some used ones for sale
soemwhere on my web page, but they are cheap), and most low power SCRs
nowadays mount via a single screw through a flange - your electronics supply
place can help you select modern parts that are electrically equivalent to
your old dead ones.


But also check space around the heat sink, to make sure that
there is room for the stud and nut in place of the press-fit. You may
have to stick with the press-fit to keep the form factor reasonable.

Check whatever was connected to the gate of the SCRs - it may have been hurt
also - typically SCRs fail short circuit, then blow an internal wire and go
open circuit (if they don't just explode their case)


Right -- make sure of everything which was connected to it.

Enjoy,
DoN.

--
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Default The devil made me do it

According to Ted Samuels :

[ ... ]

Got quite a surprise today. Tried running one of my 60 volt DC motors (I
thought they
were 90 volt motors) with a variac and my setup tripped the breaker in my power bar.
Checked and rechecked the circuits from the variac through the bridge and motor and
everything seemed logical. tried it again and again it tripped (not very smart
really). Then I happened to notice in small print on the very front of the variac
"360 cycles per minute" 6 HZ


I've never seen one of those, and I would think that one for
such a low frequency would have enough iron so it would have no troubles
with 60 Hz. Are you sure that wasn't "360 cycles per second"? That
would be close to the 400 Hz ones which I have used -- and *those* just
plain won't work with 60 Hz at normal voltage. :-)

also -- was it a genuine Variac (made by General Radio), or
another brand of variable autotransformer? The 400 Hz ones above were
genuine Variacs.

Enjoy,
DoN.
--
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(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---
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Default The devil made me do it

DoN. Nichols wrote:
According to Ted Samuels :

[ ... ]

Got quite a surprise today. Tried running one of my 60 volt DC motors (I
thought they
were 90 volt motors) with a variac and my setup tripped the breaker in my power bar.
Checked and rechecked the circuits from the variac through the bridge and motor and
everything seemed logical. tried it again and again it tripped (not very smart
really). Then I happened to notice in small print on the very front of the variac
"360 cycles per minute" 6 HZ


Oh yes. Google 6 HZ and you'll get more hits then you would ever imagine. Believe
me I had to do a double take when I read the "per minute".

I think the deal is that that there just are not enough turns to produce enough
CEMF, so at 60 hz and 110 volts the windings that are there, did not short circuit,
but really there was just to much amperage for the breaker.

T talking as if he knew something about the subject.



I've never seen one of those, and I would think that one for
such a low frequency would have enough iron so it would have no troubles
with 60 Hz. Are you sure that wasn't "360 cycles per second"? That
would be close to the 400 Hz ones which I have used -- and *those* just
plain won't work with 60 Hz at normal voltage. :-)

also -- was it a genuine Variac (made by General Radio), or
another brand of variable autotransformer? The 400 Hz ones above were
genuine Variacs.


I have no doubt. The variac is a genuine Variac.

Enjoy,
DoN.

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top posted again to annoy everyone.

1. 6 hz is almost DC - I am quite positive that the variac is not 6 hz - if
so, it would weigh an amazing amount - something else is wrong.
2. a 400 hz variac powered at 60 hz won't blow a breaker immediately, but it
will overheat rapidly (a vew seconds to smoke starts)

I would speculate that you wired it incorrectly - did you try looking up the
specific variac on the superior electric (I think that's right) web site?
can you explain exactly how you wired it? does it trip the breaker if you
disconnect the bridge?




"Ted Samuels" wrote in message
...
DoN. Nichols wrote:
According to Ted Samuels :

[ ... ]

Got quite a surprise today. Tried running one of my 60 volt DC motors (I
thought they were 90 volt motors) with a variac and my setup tripped the
breaker in my power bar. Checked and rechecked the circuits from the
variac through the bridge and motor and everything seemed logical. tried
it again and again it tripped (not very smart really). Then I happened
to notice in small print on the very front of the variac "360 cycles per
minute" 6 HZ


Oh yes. Google 6 HZ and you'll get more hits then you would ever
imagine. Believe me I had to do a double take when I read the "per
minute".

I think the deal is that that there just are not enough turns to produce
enough CEMF, so at 60 hz and 110 volts the windings that are there, did
not short circuit, but really there was just to much amperage for the
breaker.

T talking as if he knew something about the subject.



I've never seen one of those, and I would think that one for
such a low frequency would have enough iron so it would have no troubles
with 60 Hz. Are you sure that wasn't "360 cycles per second"? That
would be close to the 400 Hz ones which I have used -- and *those* just
plain won't work with 60 Hz at normal voltage. :-)

also -- was it a genuine Variac (made by General Radio), or
another brand of variable autotransformer? The 400 Hz ones above were
genuine Variacs.


I have no doubt. The variac is a genuine Variac.

Enjoy,
DoN.




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Ted Samuels wrote:
DoN. Nichols wrote:
According to Ted Samuels :

[ ... ]

Got quite a surprise today. Tried running one of my 60 volt DC motors (I
thought they were 90 volt motors) with a variac and my setup tripped the
breaker in my power bar. Checked and rechecked the circuits from the variac
through the bridge and motor and everything seemed logical. tried it again and
again it tripped (not very smart really). Then I happened to notice in small
print on the very front of the variac "360 cycles per minute" 6 HZ


Oh yes. Google 6 HZ and you'll get more hits then you would ever imagine.
Believe me I had to do a double take when I read the "per minute".

I think the deal is that that there just are not enough turns to produce enough
CEMF, so at 60 hz and 110 volts the windings that are there, did not short
circuit, but really there was just to much amperage for the breaker.

T talking as if he knew something about the subject.



I've never seen one of those, and I would think that one for such a low
frequency would have enough iron so it would have no troubles with 60 Hz. Are
you sure that wasn't "360 cycles per second"? That would be close to the 400 Hz
ones which I have used -- and *those* just plain won't work with 60 Hz at
normal voltage. :-)

also -- was it a genuine Variac (made by General Radio), or another brand of
variable autotransformer? The 400 Hz ones above were genuine Variacs.


I have no doubt. The variac is a genuine Variac.

Enjoy, DoN.


Got to correct a couple of statements I made:

1st. While this unit carries the registered "Variac (R)" name, it was made by Technipower
of Davis instruments and calibration

2nd. I initially read 350 cycles per minute but when I was on the computer I
automatically assumed that I must have read 360 CPM , (Makes more sense to me.)
On a re read I find that it actually says "350 Cycles Min."

God I hate making mistakes.

T


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William Noble wrote:
top posted again to annoy everyone.

1. 6 hz is almost DC - I am quite positive that the variac is not 6 hz - if so, it
would weigh an amazing amount - something else is wrong.


I was wrong about the 6HZ but not by much. I assumed that I was in error when I read
350 CPM and wrote 360 CPM but it was in fact 350 CPM (5.83 HZ)

2. a 400 hz variac powered at 60 hz won't blow a breaker immediately, but it will
overheat rapidly (a vew seconds to smoke starts)

I would speculate that you wired it incorrectly - did you try looking up the
specific variac on the superior electric (I think that's right) web site? can you
explain exactly how you wired it? does it trip the breaker if you disconnect the
bridge?


As I mentioned to Don : this unit carries the registered Variac(R) trademark but was
not made by superior, it was made by Technipower
of Davis instruments and calibration, type M 10, CDC part number 23253800.

Not at all in doubt about wiring as I removed that Variac and replaced it with
another and it's working just fine. The only question I have is that the motor I am
running is rated as 60 volts at 11.2 amps and the Variac is rated as 120 Volt at 6.0
amps.

I would assume I'm OK with a 672 watt load through a 720 watt transformer but maybe
there is something I am missing.

I ran continuously (no load) for 15 min and found no heating of the Variac the
bridge rectifier or the motor.

T
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Ted Samuels wrote:


As I mentioned to Don : this unit carries the registered Variac(R)
trademark but was not made by superior, it was made by Technipower


The tradename for Superior's variable transformers was Powerstat. GenRad
(the successor to General Radio) sold the "Variac" licence to
Technipower, who then sold the license to Power Designs Inc. That firm
subsequently went belly up.


Kevin Gallimore

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well, I agree something is odd about the first variac, but without either
looking at it, or a bunch of photos or something I can't tell you what. I
can tell you that I had a variac with brass holders for carbon brushes (it
had two), and one carbon brush had broken or worn off so the brass holder
contacted the windings - this caused a significant increas in current and
heating (because some windings were shorted by the brass) - there may be an
effect like this. the 350Cycles per minute nomenclature suggests that it is
a duty cycle spec not an input power spec but that's speculation on my part.
I can tell you for sure that you will NOT see a transformer rated at 350CPM
for input power frequency, so either it isnt' a transformer, or the spec is
for some other attribute other than input power.


"Ted Samuels" wrote in message
...
William Noble wrote:
top posted again to annoy everyone.

1. 6 hz is almost DC - I am quite positive that the variac is not 6 hz -
if so, it
would weigh an amazing amount - something else is wrong.


I was wrong about the 6HZ but not by much. I assumed that I was in error
when I read
350 CPM and wrote 360 CPM but it was in fact 350 CPM (5.83 HZ)

2. a 400 hz variac powered at 60 hz won't blow a breaker immediately, but
it will
overheat rapidly (a vew seconds to smoke starts)

I would speculate that you wired it incorrectly - did you try looking up
the specific variac on the superior electric (I think that's right) web
site? can you
explain exactly how you wired it? does it trip the breaker if you
disconnect the
bridge?


As I mentioned to Don : this unit carries the registered Variac(R)
trademark but was not made by superior, it was made by Technipower
of Davis instruments and calibration, type M 10, CDC part number
23253800.

Not at all in doubt about wiring as I removed that Variac and replaced it
with another and it's working just fine. The only question I have is that
the motor I am running is rated as 60 volts at 11.2 amps and the Variac is
rated as 120 Volt at 6.0 amps.

I would assume I'm OK with a 672 watt load through a 720 watt transformer
but maybe there is something I am missing.

I ran continuously (no load) for 15 min and found no heating of the
Variac the bridge rectifier or the motor.

T




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William Noble wrote:
well, I agree something is odd about the first variac, but without either
looking at it, or a bunch of photos or something I can't tell you what. I
can tell you that I had a variac with brass holders for carbon brushes (it
had two), and one carbon brush had broken or worn off so the brass holder
contacted the windings - this caused a significant increas in current and
heating (because some windings were shorted by the brass) - there may be an
effect like this. the 350Cycles per minute nomenclature suggests that it is
a duty cycle spec not an input power spec but that's speculation on my part.
I can tell you for sure that you will NOT see a transformer rated at 350CPM
for input power frequency, so either it isnt' a transformer, or the spec is
for some other attribute other than input power.

??????

Well the brush looks fine so I do not know what to say. If I had an ammeter shunt I
might dare see what current is flowing across the Variac windings.

Send me your address privately and I'll send you a close up front, side and top view
of it.

Simply replace the "." in my posted address and replace it with a "1"

T
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Default The devil made me do it

Ted Samuels wrote:

William Noble wrote:
well, I agree something is odd about the first variac, but without either
looking at it, or a bunch of photos or something I can't tell you what. I
can tell you that I had a variac with brass holders for carbon brushes (it
had two), and one carbon brush had broken or worn off so the brass holder
contacted the windings - this caused a significant increas in current and
heating (because some windings were shorted by the brass) - there may be an
effect like this. the 350Cycles per minute nomenclature suggests that it is
a duty cycle spec not an input power spec but that's speculation on my part.
I can tell you for sure that you will NOT see a transformer rated at 350CPM
for input power frequency, so either it isnt' a transformer, or the spec is
for some other attribute other than input power.

??????

Well the brush looks fine so I do not know what to say. If I had an ammeter shunt I
might dare see what current is flowing across the Variac windings.

Send me your address privately and I'll send you a close up front, side and top view
of it.

Simply replace the "." in my posted address and replace it with a "1"

T


Look at the windings. I have seen them so oxidized that the brush
couldn't make contact.


--
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prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida


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Michael A. Terrell wrote:
Ted Samuels wrote:
William Noble wrote:
well, I agree something is odd about the first variac, but without either
looking at it, or a bunch of photos or something I can't tell you what. I
can tell you that I had a variac with brass holders for carbon brushes (it
had two), and one carbon brush had broken or worn off so the brass holder
contacted the windings - this caused a significant increas in current and
heating (because some windings were shorted by the brass) - there may be an
effect like this. the 350Cycles per minute nomenclature suggests that it is
a duty cycle spec not an input power spec but that's speculation on my part.
I can tell you for sure that you will NOT see a transformer rated at 350CPM
for input power frequency, so either it isnt' a transformer, or the spec is
for some other attribute other than input power.

??????

Well the brush looks fine so I do not know what to say. If I had an ammeter shunt I
might dare see what current is flowing across the Variac windings.

Send me your address privately and I'll send you a close up front, side and top view
of it.

Simply replace the "." in my posted address and replace it with a "1"

T


Look at the windings. I have seen them so oxidized that the brush
couldn't make contact.


I think I figured out the problem. The actual wording on the front of the Variac is
"350 CYCLES Min" I took it to mean "350 CYCLES Minute" but what it probably means is
350 CYCLES Minimum.

In either case it's just not suitable for 60 Hz.

T
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Ted Samuels wrote:

I think I figured out the problem. The actual wording on the front of the Variac is
"350 CYCLES Min" I took it to mean "350 CYCLES Minute" but what it probably means is
350 CYCLES Minimum.

In either case it's just not suitable for 60 Hz.



No, that is a 400 Hz Variac, and definitely not usable on 60 Hz, but
it makes a nice volume control for a PA system with 70 or 100 volt line
transformers.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
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According to Ted Samuels :
Michael A. Terrell wrote:
Ted Samuels wrote:


[ ... ]

Look at the windings. I have seen them so oxidized that the brush
couldn't make contact.


That would have simply made the thing unable to deliver current
to the load -- no chance for that making it pop fuses or circuit
breakers.


I think I figured out the problem. The actual wording on the front of the Variac is
"350 CYCLES Min" I took it to mean "350 CYCLES Minute" but what it probably
means is
350 CYCLES Minimum.


O.K. Then it is most likely a 400 Hz one, which is what I
thought. There, there is not sufficient iron, so 60 Hz saturates it and
draws a ton of current.

In either case it's just not suitable for 60 Hz.


Agreed. Nice to have around aircraft power systems, however.

Enjoy,
DoN.

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Default The devil made me do it

DoN. Nichols wrote:
According to Ted Samuels :
Michael A. Terrell wrote:
Ted Samuels wrote:


[ ... ]

Look at the windings. I have seen them so oxidized that the brush
couldn't make contact.


That would have simply made the thing unable to deliver current
to the load -- no chance for that making it pop fuses or circuit
breakers.

I think I figured out the problem. The actual wording on the front of the Variac is
"350 CYCLES Min" I took it to mean "350 CYCLES Minute" but what it probably
means is
350 CYCLES Minimum.


O.K. Then it is most likely a 400 Hz one, which is what I
thought. There, there is not sufficient iron, so 60 Hz saturates it and
draws a ton of current.

In either case it's just not suitable for 60 Hz.


Agreed. Nice to have around aircraft power systems, however.


I bought three of them all ganged on a common shaft in the late 90s .
Took a quick look and assumed I was getting 3, 10 amp Variacs for $8.

A fool and his money are soon parted. In any case I am told that 400Hz
Variacs go for about $10 ea so nothing's lost yet, except my expectations.

T
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