160 volt 3-8 amp power supply?

[DJ Delorie]

I'm pondering a power supply for some surplus servo motors a friend
picked up. Based on testing and investigating, I'm pretty sure the
motors run on 160 volts and spec at 2.5 amps continuous stall, 7.4 amps
peak, with 5.6 ohm windings.

I've got enough experience to tell me that this is a dangerous amount of
energy

I can put together the control circuitry (mcu, mosfet drivers, etc) but
this will be my first attempt at a 1Kw+ power supply. Suggestions?

My first thoughts are : isolation transformer, maybe a 1:2 boost
transformer with a switching supply? Either that or really big capacitors.

It would be reasonable to assume I'd need to include a 3-15 volt DC
supply in there too, with a common ground, for the logic side of the
drivers, and isolate the whole thing with opto or magnetic pulse isolators.

 

[Rich Grise]

DJ Delorie wrote:

I'm pondering a power supply for some surplus servo motors a friend
picked up. Based on testing and investigating, I'm pretty sure the
motors run on 160 volts and spec at 2.5 amps continuous stall, 7.4 amps
peak, with 5.6 ohm windings.

I've got enough experience to tell me that this is a dangerous amount of
energy

I can put together the control circuitry (mcu, mosfet drivers, etc) but
this will be my first attempt at a 1Kw+ power supply. Suggestions?

My first thoughts are : isolation transformer,

Yes, absolutely!

maybe a 1:2 boost
transformer with a switching supply?

If you've never designed a switcher before, don't start now! Either buy
one and be done with it, or:

Either that or really big
capacitors.

Depending on how picky your motors are about waveform. If you use current
drivers, then you shouldn't need very smooth DC at all. I used to repair
pinball machines, and they run all the lights and solenoids off of
half-wave rectified pulsating DC, and they use SCRs for switches. I don't
know how applicable that is here - I did do a motor driver with a current
sink once, which didn't care what the input voltage was, as long as it
was more than about 18V.

It would be reasonable to assume I'd need to include a 3-15 volt DC
supply in there too, with a common ground, for the logic side of the
drivers, and isolate the whole thing with opto or magnetic pulse
isolators.

The isolation transformer (see above) will keep the whole system isolated;
as far as isolation between the control circuitry and the mongo current,
just use your own discretion. ;-)

BTW, what's a "magnetic pulse isolator?"

Have Fun!
Rich

 

[Grant]

On Fri, 05 Nov 2010 10:13:48 -0400, DJ Delorie <dj@delorie.com> wrote:

I'm pondering a power supply for some surplus servo motors a friend
picked up. Based on testing and investigating, I'm pretty sure the
motors run on 160 volts and spec at 2.5 amps continuous stall, 7.4 amps
peak, with 5.6 ohm windings.

Seems you swapped the currents there? Unless they're smart motors

I've got enough experience to tell me that this is a dangerous amount of
energy

Nah, more of a 'don't touch' voltage. 160V -> that's close to rectified mains
peak over there? Maybe an isolated drive to bridge rectified mains?

I can put together the control circuitry (mcu, mosfet drivers, etc) but
this will be my first attempt at a 1Kw+ power supply. Suggestions?

You want to reverse the motors (full bridge)?

My first thoughts are : isolation transformer, maybe a 1:2 boost
transformer with a switching supply? Either that or really big capacitors.

It would be reasonable to assume I'd need to include a 3-15 volt DC
supply in there too, with a common ground, for the logic side of the
drivers, and isolate the whole thing with opto or magnetic pulse isolators.

Something like that, depends how fine a control you're after. There's an
H-bridge topology that has the direction switches around the motor, then a
separate current controlled switching MOSFET in the negative lead of the H.

But, you'll have to search for the thing, I forgot where I saw it. Common.

Then you get to decide whether that's the way to go, or separately control
the output voltage to the H bridge. For a one-off, I wouldn't try merging
speed control into the H bridge unless you find an IC that does it all and
shows you how in the application notes.

Grant.

 

[Grant]

On Fri, 05 Nov 2010 12:04:02 -0700, Rich Grise <richg@example.net.invalid> wrote:

....

I used to repair
pinball machines, and they run all the lights and solenoids off of
half-wave rectified pulsating DC, and they use SCRs for switches.

Fun stuff, particularly the older ones. I attended the Bally seminar when
the new 6800 based machines came out -- new rules like no contact file on
the gold plated sensor contacts...

I don't
know how applicable that is here - I did do a motor driver with a current
sink once, which didn't care what the input voltage was, as long as it
was more than about 18V.

Well, since OP talks of 160V, that's a big servo probably run with the old
style rectify mains then SCR for speed control.

It would be reasonable to assume I'd need to include a 3-15 volt DC
supply in there too, with a common ground, for the logic side of the
drivers, and isolate the whole thing with opto or magnetic pulse
isolators.

The isolation transformer (see above) will keep the whole system isolated;
as far as isolation between the control circuitry and the mongo current,
just use your own discretion. ;-)

BTW, what's a "magnetic pulse isolator?"

Possibly a pulse transformer to for the SCR gates, less common for MOSFET
gate drive.

Grant.

 

[DJ Delorie]

On 11/05/2010 03:04 PM, Rich Grise wrote:

BTW, what's a "magnetic pulse isolator?"

Like an opto-isolator, but they use magnetic coupling to isolate instead
of light. Much faster switching times.

example: http://www.avagotech.com/docs/AV02-0137EN

 

[DJ Delorie]

On 11/05/2010 05:07 PM, Grant wrote:

motors run on 160 volts and spec at 2.5 amps continuous stall, 7.4 amps
peak, with 5.6 ohm windings.

Seems you swapped the currents there? Unless they're smart motors

Based on a PDF for a similar motor (same company and base part number,
but not 3-phase). If you lock the rotor, it can withstand 2.5 amps
continuously. For short-duration pulses, it can withstand up to 7.4
amps. At least that's how I interpret the specs...

I'm still iffy about the actual drive voltage. I based it on hooking
the motor to my drill press and getting 27 VAC out of the windings at
1000 RPM, then estimating the voltage needed to get it powered at full
speed with usable torque. I also compared the measurable specs with the
PDF and the motor they matched was a 160v motor.

I can put together the control circuitry (mcu, mosfet drivers, etc) but
this will be my first attempt at a 1Kw+ power supply. Suggestions?

You want to reverse the motors (full bridge)?

That's kinda the whole point of servo motors. These are three-phase
BLDC motors, not R/C servos. So, three high/low pairs per motor.

Then you get to decide whether that's the way to go, or separately control
the output voltage to the H bridge. For a one-off, I wouldn't try merging
speed control into the H bridge unless you find an IC that does it all and
shows you how in the application notes.

The MCUs I'm going to use have tons of motor control app notes, *that*
part isn't the problem. I just don't want to let the magic smoke out
before it's time...

As for the bridge itself, there are plenty of smart chips and high-v
mosfets at digikey, I don't expect that part to be too complicated.

 

[Rich Grise]

DJ Delorie wrote:

On 11/05/2010 03:04 PM, Rich Grise wrote:
BTW, what's a "magnetic pulse isolator?"

Like an opto-isolator, but they use magnetic coupling to isolate instead
of light. Much faster switching times.

example: http://www.avagotech.com/docs/AV02-0137EN

Cool!

Thanks!
Rich

 

[Bob Masta]

On Fri, 05 Nov 2010 10:13:48 -0400, DJ Delorie
<dj@delorie.com> wrote:

I'm pondering a power supply for some surplus servo motors a friend
picked up. Based on testing and investigating, I'm pretty sure the
motors run on 160 volts and spec at 2.5 amps continuous stall, 7.4 amps
peak, with 5.6 ohm windings.

I've got enough experience to tell me that this is a dangerous amount of
energy

I can put together the control circuitry (mcu, mosfet drivers, etc) but
this will be my first attempt at a 1Kw+ power supply. Suggestions?

My first thoughts are : isolation transformer, maybe a 1:2 boost
transformer with a switching supply? Either that or really big capacitors.

It would be reasonable to assume I'd need to include a 3-15 volt DC
supply in there too, with a common ground, for the logic side of the
drivers, and isolate the whole thing with opto or magnetic pulse isolators.

I don't know about big servos, but I have an industrial 1/3
HP DC motor and controller, and the heart of the controller
schematic looks an awful lot like a typical lamp dimmer. No
isolation. YMMV.

Best regards,


Bob Masta

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On Fri, 05 Nov 2010 17:24:34 -0400, DJ Delorie <dj@delorie.com> wrote:

These are three-phase
BLDC motors, not R/C servos.

The point that they are three phase should have been in the original
post. Servo motors can mean a lot of things including AC, DC, stepper
or amplidyne systems.

Three phase from zero RPM?

My guess was no one was thinking RC servo.

 

[Fred Abse]

On Fri, 05 Nov 2010 17:24:34 -0400, DJ Delorie wrote:

On 11/05/2010 05:07 PM, Grant wrote:
motors run on 160 volts and spec at 2.5 amps continuous stall, 7.4 amps
peak, with 5.6 ohm windings.

Seems you swapped the currents there? Unless they're smart motors

Based on a PDF for a similar motor (same company and base part number,
but not 3-phase). If you lock the rotor, it can withstand 2.5 amps
continuously. For short-duration pulses, it can withstand up to 7.4
amps. At least that's how I interpret the specs...

I'm still iffy about the actual drive voltage. I based it on hooking
the motor to my drill press and getting 27 VAC out of the windings at
1000 RPM, then estimating the voltage needed to get it powered at full
speed with usable torque. I also compared the measurable specs with the
PDF and the motor they matched was a 160v motor.

I can put together the control circuitry (mcu, mosfet drivers, etc) but
this will be my first attempt at a 1Kw+ power supply. Suggestions?

You want to reverse the motors (full bridge)?

That's kinda the whole point of servo motors. These are three-phase
BLDC motors, not R/C servos. So, three high/low pairs per motor.

BLDC?

Then you get to decide whether that's the way to go, or separately control
the output voltage to the H bridge. For a one-off, I wouldn't try merging
speed control into the H bridge unless you find an IC that does it all and
shows you how in the application notes.

The MCUs I'm going to use have tons of motor control app notes, *that*
part isn't the problem. I just don't want to let the magic smoke out
before it's time...

As for the bridge itself, there are plenty of smart chips and high-v
mosfets at digikey, I don't expect that part to be too complicated.

Don't use mosfets, use IGBTs

Don't control voltage, control current (ie. torque).

Power supply doesn't need regulation, just rectify and use a substantial
reservoir capacitor.

Don't forget that decelerating (braking) motors makes them regenerate. The
inertial energy has to go somewhere, like back into the DC supply.

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

[Fred Abse]

On Sat, 06 Nov 2010 08:13:22 +1100, Grant wrote:

Fun stuff, particularly the older ones. I attended the Bally seminar when
the new 6800 based machines came out -- new rules like no contact file on
the gold plated sensor contacts...

They had to *tell* you that?

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

[Fred Abse]

On Sat, 06 Nov 2010 10:08:20 -0500, default wrote:

Three phase from zero RPM?

Probably permanent magnet rotor.

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

[Michael A. Terrell]

default wrote:

On Fri, 05 Nov 2010 17:24:34 -0400, DJ Delorie <dj@delorie.com> wrote:

These are three-phase
BLDC motors, not R/C servos.

The point that they are three phase should have been in the original
post. Servo motors can mean a lot of things including AC, DC, stepper
or amplidyne systems.

Three phase from zero RPM?

My guess was no one was thinking RC servo.

Have you ever seen a RC servo that runs on 160 volts?


--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

 

On Sat, 06 Nov 2010 14:04:42 -0400, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

default wrote:

On Fri, 05 Nov 2010 17:24:34 -0400, DJ Delorie <dj@delorie.com> wrote:

These are three-phase
BLDC motors, not R/C servos.

The point that they are three phase should have been in the original
post. Servo motors can mean a lot of things including AC, DC, stepper
or amplidyne systems.

Three phase from zero RPM?

My guess was no one was thinking RC servo.


Have you ever seen a RC servo that runs on 160 volts?

Not yet.

I wonder what voltage the larger military RC airplanes use?

 

On Sat, 06 Nov 2010 09:27:07 -0700, Fred Abse
<excretatauris@invalid.invalid> wrote:

On Sat, 06 Nov 2010 10:08:20 -0500, default wrote:

Three phase from zero RPM?

Probably permanent magnet rotor.

Servo has several definitions. I think of electrical signal to
movement with feedback, but encountered its use in speed control for
things like capstan and tape reel drives too, so I didn't immediately
assume he meant it has to work from zero rpm.

The audio fringe element has something called servo feedback where the
output from a speaker (actual movement or with a microphone) is
compared to the input signal and corrected.

 

[Michael A. Terrell]

default wrote:

On Sat, 06 Nov 2010 14:04:42 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


default wrote:

On Fri, 05 Nov 2010 17:24:34 -0400, DJ Delorie <dj@delorie.com> wrote:

These are three-phase
BLDC motors, not R/C servos.

The point that they are three phase should have been in the original
post. Servo motors can mean a lot of things including AC, DC, stepper
or amplidyne systems.

Three phase from zero RPM?

My guess was no one was thinking RC servo.


Have you ever seen a RC servo that runs on 160 volts?

Not yet.

I wonder what voltage the larger military RC airplanes use?

The drones?


--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

 

[Jamie]

Fred Abse wrote:

On Fri, 05 Nov 2010 17:24:34 -0400, DJ Delorie wrote:


On 11/05/2010 05:07 PM, Grant wrote:

motors run on 160 volts and spec at 2.5 amps continuous stall, 7.4 amps
peak, with 5.6 ohm windings.

Seems you swapped the currents there? Unless they're smart motors

Based on a PDF for a similar motor (same company and base part number,
but not 3-phase). If you lock the rotor, it can withstand 2.5 amps
continuously. For short-duration pulses, it can withstand up to 7.4
amps. At least that's how I interpret the specs...

I'm still iffy about the actual drive voltage. I based it on hooking
the motor to my drill press and getting 27 VAC out of the windings at
1000 RPM, then estimating the voltage needed to get it powered at full
speed with usable torque. I also compared the measurable specs with the
PDF and the motor they matched was a 160v motor.


I can put together the control circuitry (mcu, mosfet drivers, etc) but
this will be my first attempt at a 1Kw+ power supply. Suggestions?

You want to reverse the motors (full bridge)?

That's kinda the whole point of servo motors. These are three-phase
BLDC motors, not R/C servos. So, three high/low pairs per motor.


BLDC?


Then you get to decide whether that's the way to go, or separately control
the output voltage to the H bridge. For a one-off, I wouldn't try merging
speed control into the H bridge unless you find an IC that does it all and
shows you how in the application notes.

The MCUs I'm going to use have tons of motor control app notes, *that*
part isn't the problem. I just don't want to let the magic smoke out
before it's time...

As for the bridge itself, there are plenty of smart chips and high-v
mosfets at digikey, I don't expect that part to be too complicated.


Don't use mosfets, use IGBTs

Don't control voltage, control current (ie. torque).

Power supply doesn't need regulation, just rectify and use a substantial
reservoir capacitor.

Don't forget that decelerating (braking) motors makes them regenerate. The
inertial energy has to go somewhere, like back into the DC supply.

Talking about brakes...

Today, while setting basic parms in a Baldor VS1MD drive, I found a
unique problem when using the DC brake in STOP mode. When you open the
run circuit, the DC brake operation engages like it should how ever,
while it's doing it's 6 sec applied brake of 100% current to the motor
for quick stops, in case the load is moving out of control speed and if
you vary the PID feed back reference from 0..10 or 10..0 volts, which
comes from a POT, the drive putts itself back into run mode with run
mode LED on and not flashing like it does when DC braking is being
applied. The interesting point here is, the RUN circuit is in the OFF
state as far as the external terminals are concerned and this drive is
now in a normal on state doing what it does with things are normally
does, but with the RUN REVERSE terminal (P8) not even on.. And the only
way to clear the problem is a drive repower..

This clearly looks like a firmware problem while DC braking is in
operation. Some bit must of gotten toggled on during that operation when
it saw a feed back reference error of that extreme.. Cycling the RUN
terminals does not clear the problem..

Oh well, so much for QC with the firmware..

 

[Rich Grise]

Michael A. Terrell wrote:

default wrote:
On Sat, 06 Nov 2010 14:04:42 -0400, "Michael A. Terrell"
default wrote:
On Fri, 05 Nov 2010 17:24:34 -0400, DJ Delorie <dj@delorie.com> wrote:

These are three-phase
BLDC motors, not R/C servos.

The point that they are three phase should have been in the original
post. Servo motors can mean a lot of things including AC, DC, stepper
or amplidyne systems.

Three phase from zero RPM?

My guess was no one was thinking RC servo.

Have you ever seen a RC servo that runs on 160 volts?

Not yet.

I wonder what voltage the larger military RC airplanes use?

The drones?

Probably any of these:
http://www.fas.org/irp/program/collect/uav.htm

From the size of them, it looks like a lot of them would use the standard
120V, 400~ 3-phase and 28VDC.

But I wouldn't be surprised to find that the really small ones use something
similar to the Futaba hobby RC stuff.

So, essentially, I'm guessing. ;-)

Cheers!
Rich

 

[DJ Delorie]

I need to remember to read news more often...

On 11/06/2010 11:08 AM, default wrote:

The point that they are three phase should have been in the original
post. Servo motors can mean a lot of things including AC, DC, stepper
or amplidyne systems.

That changes the power supply design? I can manage the control side of
this, it's the 1000 Watt power supply I'm worried about, or if I'm way
off in my power estimates.

Three phase from zero RPM?

Well, these have 1000-step quadrature encoders on them, I suppose with
enough finesse you could control the position down to a dead stop. The
guy who picked them was thinking CNC.

My guess was no one was thinking RC servo.

 

[DJ Delorie]

On 11/06/2010 12:09 PM, Fred Abse wrote:

BLDC?

Brushless DC. Wired like a three-phase AC motor, but designed to be
driven by a phase-controlled DC signal with a feedback loop from some
sort of shaft-position-sensor. Magnets in the rotor, coils fixed in the
stator.