I found a DC power supply among the stuff that I had. This is a Syncor
PP-1659A/G military power supply called "battery charger". It is a multitap
transformer and a rectifier. Goes up to 150 volts and up to 20 amps.

I fixed up whatever physical damage it had (missing banana plug) and
now it seems to work well, except that on some settings it does not
seem to have good contact. Probably needs some multitap contacts
cleaned.

Anyway, I can set it to, say, 76 volts DC and just user it? Do I need
to put in any capacitors, since this is a pretty bare rectifier?

i

use it for what? the application will determine the required purity of the
DC

"Ignoramus14096" wrote in message
...
I found a DC power supply among the stuff that I had. This is a Syncor
PP-1659A/G military power supply called "battery charger". It is a
multitap
transformer and a rectifier. Goes up to 150 volts and up to 20 amps.

I fixed up whatever physical damage it had (missing banana plug) and
now it seems to work well, except that on some settings it does not
seem to have good contact. Probably needs some multitap contacts
cleaned.

Anyway, I can set it to, say, 76 volts DC and just user it? Do I need
to put in any capacitors, since this is a pretty bare rectifier?

i

On 2010-06-08, Bill Noble wrote:
use it for what? the application will determine the required purity of the
DC

for running servo motors via amplifiers.

i

"Ignoramus14096" wrote in message
...
I found a DC power supply among the stuff that I had. This is a Syncor
PP-1659A/G military power supply called "battery charger". It is a
multitap
transformer and a rectifier. Goes up to 150 volts and up to 20 amps.

I fixed up whatever physical damage it had (missing banana plug) and
now it seems to work well, except that on some settings it does not
seem to have good contact. Probably needs some multitap contacts
cleaned.

Anyway, I can set it to, say, 76 volts DC and just user it? Do I need
to put in any capacitors, since this is a pretty bare rectifier?

i

Ignoramus14096 wrote:

On 2010-06-08, Bill Noble wrote:
use it for what? the application will determine the required purity of the
DC

for running servo motors via amplifiers.


Only if you want to fry them. The amplifiers need a well filtered
power source. Regulated is even better. What you have is not much more
than a battery charger.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

ok, to run servos you don't need all that much filtering, but how much
depends on the specific amplifier topology - you can try it unfiltered, and
so long as you stay below the limits of the transistors, you will do no
harm - if the system seems sluggish or unstable, add filtering - the caps do
more than just remove ripple, they also provide a surge current capability

"Ignoramus14096" wrote in message
...
On 2010-06-08, Bill Noble wrote:
use it for what? the application will determine the required purity of
the
DC

for running servo motors via amplifiers.

i

"Ignoramus14096" wrote in message
...
I found a DC power supply among the stuff that I had. This is a Syncor
PP-1659A/G military power supply called "battery charger". It is a
multitap
transformer and a rectifier. Goes up to 150 volts and up to 20 amps.

I fixed up whatever physical damage it had (missing banana plug) and
now it seems to work well, except that on some settings it does not
seem to have good contact. Probably needs some multitap contacts
cleaned.

Anyway, I can set it to, say, 76 volts DC and just user it? Do I need
to put in any capacitors, since this is a pretty bare rectifier?

i

"Ignoramus14096" wrote in message
...
I found a DC power supply among the stuff that I had. This is a Syncor
PP-1659A/G military power supply called "battery charger". It is a
multitap
transformer and a rectifier. Goes up to 150 volts and up to 20 amps.

I fixed up whatever physical damage it had (missing banana plug) and
now it seems to work well, except that on some settings it does not
seem to have good contact. Probably needs some multitap contacts
cleaned.

Anyway, I can set it to, say, 76 volts DC and just user it? Do I need
to put in any capacitors, since this is a pretty bare rectifier?

i

Iggy, electrolytic caps are really cheap. just add some. This web site has
an explanation of how big a unit to get.
http://www.kpsec.freeuk.com/powersup.htm

"Ignoramus14096" wrote in message
...
On 2010-06-08, Bill Noble wrote:
use it for what? the application will determine the required purity of
the
DC

for running servo motors via amplifiers.

i

snip

Are you using the existing amplifiers? If so, do they have a power supply
already?

On my EMC2 conversion I was able to use the existing amplifiers, servos,
encoders, power supply, I just changed the control, saved some money. Looks
like you have some hopefully good encoders on the way, especially if they
fit where the old encoders were.


RogerN

On 2010-06-08, RogerN wrote:

"Ignoramus14096" wrote in message
...
On 2010-06-08, Bill Noble wrote:
use it for what? the application will determine the required purity of
the
DC

for running servo motors via amplifiers.

i

snip

Are you using the existing amplifiers? If so, do they have a power supply
already?

I do not yet know. I have existing amplifiers, and also three AMC
amplifiers that I bought inexpensively.

I am not sure how I wuold figure out the wiring for existing
amplifiers, but there is a chance that I can do so.

The hope that I have in gutting the existing stuff, is that I can also
switch to single phase and end up with a system that I understand.

On my EMC2 conversion I was able to use the existing amplifiers, servos,
encoders, power supply, I just changed the control, saved some money. Looks
like you have some hopefully good encoders on the way, especially if they
fit where the old encoders were.

I hope so.

i

On 2010-06-08, Karl Townsend wrote:

"Ignoramus14096" wrote in message
...
I found a DC power supply among the stuff that I had. This is a Syncor
PP-1659A/G military power supply called "battery charger". It is a
multitap
transformer and a rectifier. Goes up to 150 volts and up to 20 amps.

I fixed up whatever physical damage it had (missing banana plug) and
now it seems to work well, except that on some settings it does not
seem to have good contact. Probably needs some multitap contacts
cleaned.

Anyway, I can set it to, say, 76 volts DC and just user it? Do I need
to put in any capacitors, since this is a pretty bare rectifier?

i

Iggy, electrolytic caps are really cheap. just add some. This web site has
an explanation of how big a unit to get.
http://www.kpsec.freeuk.com/powersup.htm




I got two 10,000 uF capacitors from digikey, 100v max, 18000 hours
life. When charging the caps niitially, would the diodes be stressed?

i

On Tue, 08 Jun 2010 08:27:46 -0500, Ignoramus8975
wrote:

On 2010-06-08, Karl Townsend wrote:

"Ignoramus14096" wrote in message
...
I found a DC power supply among the stuff that I had. This is a Syncor
PP-1659A/G military power supply called "battery charger". It is a
multitap
transformer and a rectifier. Goes up to 150 volts and up to 20 amps.

I fixed up whatever physical damage it had (missing banana plug) and
now it seems to work well, except that on some settings it does not
seem to have good contact. Probably needs some multitap contacts
cleaned.

Anyway, I can set it to, say, 76 volts DC and just user it? Do I need
to put in any capacitors, since this is a pretty bare rectifier?

i

Iggy, electrolytic caps are really cheap. just add some. This web site has
an explanation of how big a unit to get.
http://www.kpsec.freeuk.com/powersup.htm




I got two 10,000 uF capacitors from digikey, 100v max, 18000 hours
life. When charging the caps niitially, would the diodes be stressed?

Oversize the diodes; large rectifier bridges are dirt cheap. I've buit
many supplies for AMC and Copley servo amps with just a transformer,
rectifier bridge and cap and never had a problem. Oh, and don't forget
a bleed resistor for the cap.

--
Ned Simmons

On 06/07/2010 10:09 PM, Ignoramus14096 wrote:
I found a DC power supply among the stuff that I had. This is a Syncor
PP-1659A/G military power supply called "battery charger". It is a multitap
transformer and a rectifier. Goes up to 150 volts and up to 20 amps.

I fixed up whatever physical damage it had (missing banana plug) and
now it seems to work well, except that on some settings it does not
seem to have good contact. Probably needs some multitap contacts
cleaned.

Anyway, I can set it to, say, 76 volts DC and just user it? Do I need
to put in any capacitors, since this is a pretty bare rectifier?

It may work great, but if you didn't remove any resistors from it you
may find that it has poor regulation under a varying load. Most battery
chargers need some sort of current limiting; you can do this in the
transformer by designing in a healthy amount of leakage inductance
(microwave oven power transformers usually have a slug of transformer
material wedged or spot-welded into the core between primary and
secondary for this purpose). So you may find that the transformer it
inherently incapable of good regulation.

And poor regulation to your servo amplifiers could cause all sorts of
weird problems.

I'd try it, but I wouldn't be surprised if it wasn't good enough.

And yes, put some filter caps in there.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

On 2010-06-08, Tim Wescott wrote:
It may work great, but if you didn't remove any resistors from it you
may find that it has poor regulation under a varying load. Most battery
chargers need some sort of current limiting; you can do this in the
transformer by designing in a healthy amount of leakage inductance
(microwave oven power transformers usually have a slug of transformer
material wedged or spot-welded into the core between primary and
secondary for this purpose). So you may find that the transformer it
inherently incapable of good regulation.

And poor regulation to your servo amplifiers could cause all sorts of
weird problems.

I'd try it, but I wouldn't be surprised if it wasn't good enough.

And yes, put some filter caps in there.


Tim, how can I test it? Can I, say, make it produce, say, 15 amps of
current, and I would watch the voltmeter to see if it sags a lot?

i

On 06/08/2010 08:26 AM, Ignoramus8975 wrote:
On 2010-06-08, Tim wrote:
It may work great, but if you didn't remove any resistors from it you
may find that it has poor regulation under a varying load. Most battery
chargers need some sort of current limiting; you can do this in the
transformer by designing in a healthy amount of leakage inductance
(microwave oven power transformers usually have a slug of transformer
material wedged or spot-welded into the core between primary and
secondary for this purpose). So you may find that the transformer it
inherently incapable of good regulation.

And poor regulation to your servo amplifiers could cause all sorts of
weird problems.

I'd try it, but I wouldn't be surprised if it wasn't good enough.

And yes, put some filter caps in there.


Tim, how can I test it? Can I, say, make it produce, say, 15 amps of
current, and I would watch the voltmeter to see if it sags a lot?

Yes. That's the test for voltage sag. Testing it without the filter
caps will measure the sag from the transformer. With filter caps you
have an effect that can either be described as "ripple causing sag" or
"ripple that looks like sag" depending on your point of view, but which
is, in either case, a ripple whose high-voltage point doesn't change
much but whose low-voltage point sags more and more with increasing current.

You'll be measuring a pulsating DC voltage; some (really cheap) digital
voltmeters will jump around a lot measuring that, others will be steady
(analog voltmeters will be rock steady). If you voltmeter jumps around
a lot then try another one, or post again and I'll show you a low-pass
filter that'll steady it out.

The servo amplifiers will be able to tolerate some sag -- they're
designed to work with power supplies that have considerable ripple, and
to them ripple and sag are the same thing. But they'll also have some
input voltage limit below which they're just not going to work right,
and that input voltage is going to be reached when you're asking for the
most torque from your motors.

Basically, you want the lowest instantaneous voltage out of the supply
to be above whatever the amplifiers needs, without letting the highest
instantaneous voltage out of the supply exceed whatever the amplifiers
can stand. You can compensate for some amount of sag by putting in
honking big filter caps -- that'll reduce the ripple, which gives you
more room for sag. The best part is that the more current limiting you
have in the transformer, the more you can just load in the filter caps
without worrying about the power factor of the current, because the
transformer will be taking care of that.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

I got two 10,000 uF capacitors from digikey, 100v max, 18000 hours
life. When charging the caps niitially, would the diodes be stressed?

Oversize the diodes; large rectifier bridges are dirt cheap. I've buit
many supplies for AMC and Copley servo amps with just a transformer,
rectifier bridge and cap and never had a problem. Oh, and don't forget
a bleed resistor for the cap.

Ah, come on. You're spoiling Iggy's fun. I got zapped by an electrolytic cap
once. Gets your attention, and then you learn all about bleed resistors and
never forget them.

Karl

On Tue, 08 Jun 2010 10:06:46 -0400, Ned Simmons wrote:

On Tue, 08 Jun 2010 08:27:46 -0500, Ignoramus8975
wrote:

On 2010-06-08, Karl Townsend wrote:

"Ignoramus14096" wrote in message
...
I found a DC power supply among the stuff that I had. This is a Syncor
PP-1659A/G military power supply called "battery charger". It is a
multitap
transformer and a rectifier. Goes up to 150 volts and up to 20 amps.

I fixed up whatever physical damage it had (missing banana plug) and
now it seems to work well, except that on some settings it does not
seem to have good contact. Probably needs some multitap contacts
cleaned.

Anyway, I can set it to, say, 76 volts DC and just user it? Do I need
to put in any capacitors, since this is a pretty bare rectifier?

i

Iggy, electrolytic caps are really cheap. just add some. This web site has
an explanation of how big a unit to get.
http://www.kpsec.freeuk.com/powersup.htm




I got two 10,000 uF capacitors from digikey, 100v max, 18000 hours
life. When charging the caps niitially, would the diodes be stressed?

Oversize the diodes; large rectifier bridges are dirt cheap. I've buit
many supplies for AMC and Copley servo amps with just a transformer,
rectifier bridge and cap and never had a problem. Oh, and don't forget
a bleed resistor for the cap.

The OmniTurn CNC controls have a big toroid transformer, a moderate
sized bridge rectifier and a decent sized single cap to run the servos.

Works just fine with both AMC and Copely amps. Also the Glentec amps are
the current amps supplied. Very versitile amp.

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On 2010-06-08, Karl Townsend wrote:

I got two 10,000 uF capacitors from digikey, 100v max, 18000 hours
life. When charging the caps niitially, would the diodes be stressed?

Oversize the diodes; large rectifier bridges are dirt cheap. I've buit
many supplies for AMC and Copley servo amps with just a transformer,
rectifier bridge and cap and never had a problem. Oh, and don't forget
a bleed resistor for the cap.

Ah, come on. You're spoiling Iggy's fun. I got zapped by an electrolytic cap
once. Gets your attention, and then you learn all about bleed resistors and
never forget them.


I actually already know (though I was not zapped). I learned many
things the hard way, but not this one.

i

On 06/08/2010 07:06 AM, Ned Simmons wrote:
On Tue, 08 Jun 2010 08:27:46 -0500, Ignoramus8975
wrote:

On 2010-06-08, Karl wrote:

id wrote in message
...
I found a DC power supply among the stuff that I had. This is a Syncor
PP-1659A/G military power supply called "battery charger". It is a
multitap
transformer and a rectifier. Goes up to 150 volts and up to 20 amps.

I fixed up whatever physical damage it had (missing banana plug) and
now it seems to work well, except that on some settings it does not
seem to have good contact. Probably needs some multitap contacts
cleaned.

Anyway, I can set it to, say, 76 volts DC and just user it? Do I need
to put in any capacitors, since this is a pretty bare rectifier?

i

Iggy, electrolytic caps are really cheap. just add some. This web site has
an explanation of how big a unit to get.
http://www.kpsec.freeuk.com/powersup.htm




I got two 10,000 uF capacitors from digikey, 100v max, 18000 hours
life. When charging the caps niitially, would the diodes be stressed?

Oversize the diodes; large rectifier bridges are dirt cheap. I've buit
many supplies for AMC and Copley servo amps with just a transformer,
rectifier bridge and cap and never had a problem. Oh, and don't forget
a bleed resistor for the cap.

If the transformer really does have poor voltage regulation as theorized
in other parts of this thread, then the oversized rectifiers would be
unnecessary.

Bleed resistors take much of the excitement out of life.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

On 2010-06-08, Ned Simmons wrote:
On Tue, 08 Jun 2010 08:27:46 -0500, Ignoramus8975
wrote:

On 2010-06-08, Karl Townsend wrote:

"Ignoramus14096" wrote in message
...
I found a DC power supply among the stuff that I had. This is a Syncor
PP-1659A/G military power supply called "battery charger". It is a
multitap
transformer and a rectifier. Goes up to 150 volts and up to 20 amps.

I fixed up whatever physical damage it had (missing banana plug) and
now it seems to work well, except that on some settings it does not
seem to have good contact. Probably needs some multitap contacts
cleaned.

Anyway, I can set it to, say, 76 volts DC and just user it? Do I need
to put in any capacitors, since this is a pretty bare rectifier?

i

Iggy, electrolytic caps are really cheap. just add some. This web site has
an explanation of how big a unit to get.
http://www.kpsec.freeuk.com/powersup.htm




I got two 10,000 uF capacitors from digikey, 100v max, 18000 hours
life. When charging the caps niitially, would the diodes be stressed?

Oversize the diodes; large rectifier bridges are dirt cheap. I've buit
many supplies for AMC and Copley servo amps with just a transformer,
rectifier bridge and cap and never had a problem. Oh, and don't forget
a bleed resistor for the cap.


After a bit of thinking, I began to realize that the whole setup is
limited by the transformer, and so, putting lathe caps on output would
not be likely to ruin the existing diodes. I will try turning it off
and on a few times. If the diodes fail I will oversize them.

On 2010-06-08, Tim Wescott wrote:
On 06/08/2010 08:26 AM, Ignoramus8975 wrote:
On 2010-06-08, Tim wrote:
It may work great, but if you didn't remove any resistors from it you
may find that it has poor regulation under a varying load. Most battery
chargers need some sort of current limiting; you can do this in the
transformer by designing in a healthy amount of leakage inductance
(microwave oven power transformers usually have a slug of transformer
material wedged or spot-welded into the core between primary and
secondary for this purpose). So you may find that the transformer it
inherently incapable of good regulation.

And poor regulation to your servo amplifiers could cause all sorts of
weird problems.

I'd try it, but I wouldn't be surprised if it wasn't good enough.

And yes, put some filter caps in there.


Tim, how can I test it? Can I, say, make it produce, say, 15 amps of
current, and I would watch the voltmeter to see if it sags a lot?

Yes. That's the test for voltage sag. Testing it without the filter
caps will measure the sag from the transformer. With filter caps you
have an effect that can either be described as "ripple causing sag" or
"ripple that looks like sag" depending on your point of view, but which
is, in either case, a ripple whose high-voltage point doesn't change
much but whose low-voltage point sags more and more with increasing current.

You'll be measuring a pulsating DC voltage; some (really cheap) digital
voltmeters will jump around a lot measuring that, others will be steady
(analog voltmeters will be rock steady). If you voltmeter jumps around
a lot then try another one, or post again and I'll show you a low-pass
filter that'll steady it out.

The servo amplifiers will be able to tolerate some sag -- they're
designed to work with power supplies that have considerable ripple, and
to them ripple and sag are the same thing. But they'll also have some
input voltage limit below which they're just not going to work right,
and that input voltage is going to be reached when you're asking for the
most torque from your motors.

Basically, you want the lowest instantaneous voltage out of the supply
to be above whatever the amplifiers needs, without letting the highest
instantaneous voltage out of the supply exceed whatever the amplifiers
can stand. You can compensate for some amount of sag by putting in
honking big filter caps -- that'll reduce the ripple, which gives you
more room for sag. The best part is that the more current limiting you
have in the transformer, the more you can just load in the filter caps
without worrying about the power factor of the current, because the
transformer will be taking care of that.


Tim, OK, that makes sense to me. Now, what is the easiest way to
consume 15 amps of DC at 80 volts for a few seconds? I may try some
big wirewound resistors that I have

i

On Tue, 8 Jun 2010 11:17:31 -0500, "Karl Townsend"
wrote:
SNIP

............................... Oh, and don't forget
a bleed resistor for the cap.

Ah, come on. You're spoiling Iggy's fun. I got zapped by an electrolytic cap
once. Gets your attention, and then you learn all about bleed resistors and
never forget them.

Karl

Hey Karl,

Ha ha ha. I can't tell you how many fairly decent "injuries" loaded
caps have caused. Not from the voltage you catch, but from the
mechanic reaching into a controller cabinet, getting a "zap" and then
REALLY banging or scraping or even slicing an elbow or their head or
something else when they "jerk" that body part out and hit the cabinet
or a bracket or a screw or some other hard/sharp part of the
controller cabinet !!! Stitches required a number of times.

Lot of caps are used as timers on elevators, so don't have the bleeder
resistor, and when the power is pulled the normal discharge path is
opened, so they stay charged. I think maybe the fact that the power
is supposedly "off" is what causes the violent reaction....makes you
think, in that less than a split-second, that maybe you hadn't turned
everything off, and that maybe you got into the 575 volts or
something.

Brian Lawson,
Bothwell, Ontario.

ps....of course, it's never happened to me. Yeah!! Riiiigghhhtttt !!

On 06/08/2010 10:05 AM, Brian Lawson wrote:
On Tue, 8 Jun 2010 11:17:31 -0500, "Karl Townsend"
wrote:
SNIP

............................... Oh, and don't forget
a bleed resistor for the cap.

Ah, come on. You're spoiling Iggy's fun. I got zapped by an electrolytic cap
once. Gets your attention, and then you learn all about bleed resistors and
never forget them.

Karl

Hey Karl,

Ha ha ha. I can't tell you how many fairly decent "injuries" loaded
caps have caused. Not from the voltage you catch, but from the
mechanic reaching into a controller cabinet, getting a "zap" and then
REALLY banging or scraping or even slicing an elbow or their head or
something else when they "jerk" that body part out and hit the cabinet
or a bracket or a screw or some other hard/sharp part of the
controller cabinet !!! Stitches required a number of times.

Lot of caps are used as timers on elevators, so don't have the bleeder
resistor, and when the power is pulled the normal discharge path is
opened, so they stay charged. I think maybe the fact that the power
is supposedly "off" is what causes the violent reaction....makes you
think, in that less than a split-second, that maybe you hadn't turned
everything off, and that maybe you got into the 575 volts or
something.

Brian Lawson,
Bothwell, Ontario.

ps....of course, it's never happened to me. Yeah!! Riiiigghhhtttt !!

So, you didn't go around with the "discharge stick" and make everything
safe?

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

On Tue, 08 Jun 2010 08:51:50 -0700, Tim Wescott
wrote:


The servo amplifiers will be able to tolerate some sag -- they're
designed to work with power supplies that have considerable ripple, and
to them ripple and sag are the same thing. But they'll also have some
input voltage limit below which they're just not going to work right,
and that input voltage is going to be reached when you're asking for the
most torque from your motors.

Which brings up another function of the caps, which is to absorb
energy returned from the motor when it's decelerating a load. It's
possible to fault the amp by exceeding its input voltage limit if the
caps aren't large enough. A case like lowering a suspended load is
worse than decelerating a mill axis, but it's something to keep in
mind.

--
Ned Simmons

On 2010-06-08, Tim Wescott wrote:
Ah, come on. You're spoiling Iggy's fun. I got zapped by an electrolytic cap
once. Gets your attention, and then you learn all about bleed resistors and
never forget them.
Ha ha ha. I can't tell you how many fairly decent "injuries" loaded
caps have caused. Not from the voltage you catch, but from the
mechanic reaching into a controller cabinet, getting a "zap" and then
REALLY banging or scraping or even slicing an elbow or their head or
something else when they "jerk" that body part out and hit the cabinet
or a bracket or a screw or some other hard/sharp part of the
controller cabinet !!! Stitches required a number of times.

Lot of caps are used as timers on elevators, so don't have the bleeder
resistor, and when the power is pulled the normal discharge path is
opened, so they stay charged. I think maybe the fact that the power
is supposedly "off" is what causes the violent reaction....makes you
think, in that less than a split-second, that maybe you hadn't turned
everything off, and that maybe you got into the 575 volts or
something.

So, you didn't go around with the "discharge stick" and make everything
safe?



I never was stung by a charged cap. However, once I did short a cap
with a screwdriver, just in case, as I was sure it was discharged.
It was very LOUD!

i

On 2010-06-08, Ned Simmons wrote:
On Tue, 08 Jun 2010 08:51:50 -0700, Tim Wescott
wrote:


The servo amplifiers will be able to tolerate some sag -- they're
designed to work with power supplies that have considerable ripple, and
to them ripple and sag are the same thing. But they'll also have some
input voltage limit below which they're just not going to work right,
and that input voltage is going to be reached when you're asking for the
most torque from your motors.

Which brings up another function of the caps, which is to absorb
energy returned from the motor when it's decelerating a load. It's
possible to fault the amp by exceeding its input voltage limit if the
caps aren't large enough. A case like lowering a suspended load is
worse than decelerating a mill axis, but it's something to keep in
mind.


I may get the caps tomorrow, in which case I will give the device a
try. I have some caps (not exactly suitable, 50v) that I can try today
for experimenting.

i

Too large a filter cap -- excessive surge current -- blown rectifier, or worse. Iggy, these things
are well covered in Eng. design handbooks.

Bob Swinney
"Ignoramus8975" wrote in message
...
On 2010-06-08, Ned Simmons wrote:
On Tue, 08 Jun 2010 08:27:46 -0500, Ignoramus8975
wrote:

On 2010-06-08, Karl Townsend wrote:

"Ignoramus14096" wrote in message
...
I found a DC power supply among the stuff that I had. This is a Syncor
PP-1659A/G military power supply called "battery charger". It is a
multitap
transformer and a rectifier. Goes up to 150 volts and up to 20 amps.

I fixed up whatever physical damage it had (missing banana plug) and
now it seems to work well, except that on some settings it does not
seem to have good contact. Probably needs some multitap contacts
cleaned.

Anyway, I can set it to, say, 76 volts DC and just user it? Do I need
to put in any capacitors, since this is a pretty bare rectifier?

i

Iggy, electrolytic caps are really cheap. just add some. This web site has
an explanation of how big a unit to get.
http://www.kpsec.freeuk.com/powersup.htm




I got two 10,000 uF capacitors from digikey, 100v max, 18000 hours
life. When charging the caps niitially, would the diodes be stressed?

Oversize the diodes; large rectifier bridges are dirt cheap. I've buit
many supplies for AMC and Copley servo amps with just a transformer,
rectifier bridge and cap and never had a problem. Oh, and don't forget
a bleed resistor for the cap.


After a bit of thinking, I began to realize that the whole setup is
limited by the transformer, and so, putting lathe caps on output would
not be likely to ruin the existing diodes. I will try turning it off
and on a few times. If the diodes fail I will oversize them.

On 2010-06-08, Robert Swinney wrote:
Too large a filter cap -- excessive surge current -- blown rectifier, or worse. Iggy, these things
are well covered in Eng. design handbooks.


Bob, would not the transformer limit current?

i

"Ignoramus8975" wrote in message
...
On 2010-06-08, Ned Simmons wrote:
On Tue, 08 Jun 2010 08:27:46 -0500, Ignoramus8975
wrote:

On 2010-06-08, Karl Townsend wrote:

"Ignoramus14096" wrote in message
...
I found a DC power supply among the stuff that I had. This is a Syncor
PP-1659A/G military power supply called "battery charger". It is a
multitap
transformer and a rectifier. Goes up to 150 volts and up to 20 amps.

I fixed up whatever physical damage it had (missing banana plug) and
now it seems to work well, except that on some settings it does not
seem to have good contact. Probably needs some multitap contacts
cleaned.

Anyway, I can set it to, say, 76 volts DC and just user it? Do I need
to put in any capacitors, since this is a pretty bare rectifier?

i

Iggy, electrolytic caps are really cheap. just add some. This web site has
an explanation of how big a unit to get.
http://www.kpsec.freeuk.com/powersup.htm




I got two 10,000 uF capacitors from digikey, 100v max, 18000 hours
life. When charging the caps niitially, would the diodes be stressed?

Oversize the diodes; large rectifier bridges are dirt cheap. I've buit
many supplies for AMC and Copley servo amps with just a transformer,
rectifier bridge and cap and never had a problem. Oh, and don't forget
a bleed resistor for the cap.


After a bit of thinking, I began to realize that the whole setup is
limited by the transformer, and so, putting lathe caps on output would
not be likely to ruin the existing diodes. I will try turning it off
and on a few times. If the diodes fail I will oversize them.

Ignoramus8975 wrote:

On 2010-06-08, Ned Simmons wrote:
On Tue, 08 Jun 2010 08:51:50 -0700, Tim Wescott
wrote:


The servo amplifiers will be able to tolerate some sag -- they're
designed to work with power supplies that have considerable ripple, and
to them ripple and sag are the same thing. But they'll also have some
input voltage limit below which they're just not going to work right,
and that input voltage is going to be reached when you're asking for the
most torque from your motors.

Which brings up another function of the caps, which is to absorb
energy returned from the motor when it's decelerating a load. It's
possible to fault the amp by exceeding its input voltage limit if the
caps aren't large enough. A case like lowering a suspended load is
worse than decelerating a mill axis, but it's something to keep in
mind.


I may get the caps tomorrow, in which case I will give the device a
try. I have some caps (not exactly suitable, 50v) that I can try today
for experimenting.


50/1.414 = 35.36 RMS at the transformer plus the diode drops. Start
at a lower voltage, if you're not trying to turn those capacitors into
confetti and the cans into projectiles.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

Ignoramus8975 wrote:

On 2010-06-08, Robert Swinney wrote:
Too large a filter cap -- excessive surge current -- blown rectifier, or worse. Iggy, these things
are well covered in Eng. design handbooks.


Bob, would not the transformer limit current?


Not for a single motor. A transformer's ability to limit current is
based on the DC resistance of the windings.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

On 2010-06-08, Michael A. Terrell wrote:

Ignoramus8975 wrote:

On 2010-06-08, Robert Swinney wrote:
Too large a filter cap -- excessive surge current -- blown rectifier, or worse. Iggy, these things
are well covered in Eng. design handbooks.


Bob, would not the transformer limit current?


Not for a single motor. A transformer's ability to limit current is
based on the DC resistance of the windings.



OK, what motor?

i

On 06/08/2010 02:56 PM, Michael A. Terrell wrote:

Ignoramus8975 wrote:

On 2010-06-08, Robert wrote:
Too large a filter cap -- excessive surge current -- blown rectifier, or worse. Iggy, these things
are well covered in Eng. design handbooks.


Bob, would not the transformer limit current?


Not for a single motor. A transformer's ability to limit current is
based on the DC resistance of the windings.

Or leakage inductance.


--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

Ignoramus8975 wrote:

On 2010-06-08, Michael A. Terrell wrote:

Ignoramus8975 wrote:

On 2010-06-08, Robert Swinney wrote:
Too large a filter cap -- excessive surge current -- blown rectifier, or worse. Iggy, these things
are well covered in Eng. design handbooks.


Bob, would not the transformer limit current?


Not for a single motor. A transformer's ability to limit current is
based on the DC resistance of the windings.



OK, what motor?


The motor you are trying to test? Its current loading is below what
the transformer can supply, so the transformer can not limit current.
That's why the circuit breakers in your home are rated for 10,000 A
interrupting capacity.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

Mike sez:

" . . .if you're not trying to turn those capacitors into
confetti and the cans into projectiles."

Caps can be dangerous alright. I remember an incident from a military class on HV (radar) power
supplies. The class clown got knocked on his ass by touching the wrong part of the (experiment)
power supply. As he was picking himself up off the floor and when he cleared the edge of the
workbench, a cap blew and he got slapped between the eyes with part of the cap's aluminum case.
Down he went, again.

Bob Swinney

On Tue, 08 Jun 2010 10:26:12 -0500, Ignoramus8975
wrote the following:

On 2010-06-08, Tim Wescott wrote:
It may work great, but if you didn't remove any resistors from it you
may find that it has poor regulation under a varying load. Most battery
chargers need some sort of current limiting; you can do this in the
transformer by designing in a healthy amount of leakage inductance
(microwave oven power transformers usually have a slug of transformer
material wedged or spot-welded into the core between primary and
secondary for this purpose). So you may find that the transformer it
inherently incapable of good regulation.

And poor regulation to your servo amplifiers could cause all sorts of
weird problems.

I'd try it, but I wouldn't be surprised if it wasn't good enough.

And yes, put some filter caps in there.


Tim, how can I test it? Can I, say, make it produce, say, 15 amps of
current, and I would watch the voltmeter to see if it sags a lot?

Well, if you touch the leads to your tongue...
..
..
..
..
CAUTION: KIDS, DON'T TRY THIS AT HOME!



--
Never tell people how to do things. Tell them what
to do and they will surprise you with their ingenuity.
-- George S. Patton

Ignoramus8975 writes:

Tim, how can I test it? Can I, say, make it produce, say, 15 amps of
current, and I would watch the voltmeter to see if it sags a lot?

Look, if you're using digital encoders and controllers, the DC input does
not have to be regulated, and a gutsy toroid plus fullwave bridge and a
modest capacitance is fine. The digital servo controller is itself a
regulator by nature. The input DC can sag and ripple as long as you have
enough volts there to meet the speed demand and current for the torque
demand. The controller's digital feedback loop responds much faster than
any sag or hum frequencies.

Robert Swinney wrote:

Mike sez:

" . . .if you're not trying to turn those capacitors into
confetti and the cans into projectiles."

Caps can be dangerous alright. I remember an incident from a military class on HV (radar) power
supplies. The class clown got knocked on his ass by touching the wrong part of the (experiment)
power supply. As he was picking himself up off the floor and when he cleared the edge of the
workbench, a cap blew and he got slapped between the eyes with part of the cap's aluminum case.
Down he went, again.


Some of those large computer grade electrolytics could cause a
concussion, or even kill you if you're careless enough. I had a hell of
a time teaching some people to test low voltage linear power supplies
with a variac. They insisted on setting it at 120 VAc, then flipping
the power switch. If one of the nine electrolytics was installed
backwards, you didn't have time to turn it off before they vented.
Luckily, they had a 1/8" plate bolted down to keep them in place.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.