Old discussion on SED, tracking original post...

[Klaus Kragelund]

Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I found more or less nothing on google. Then I tried the archived SED at google groups, and found a nice thread where John Woodgate has done some work:

https://groups.google.com/g/sci.electronics.design/c/4Aa6TU8E3po/m/oUuAz3pQXksJ

The thread starts with Winfield Hill quoting measurements John did. So tried to see if I could find the original post, but have been unable to find any.

The thread is from 1998. Is there any way to look up all posts by Woodgate, so I can track it? (maybe it is posted not on SED)

Regards

Klaus

 

[Klaus Vestergaard Kragelund]

On 25-06-2023 01:31, Klaus Kragelund wrote:

Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I found more or less nothing on google. Then I tried the archived SED at google groups, and found a nice thread where John Woodgate has done some work:

https://groups.google.com/g/sci.electronics.design/c/4Aa6TU8E3po/m/oUuAz3pQXksJ

The thread starts with Winfield Hill quoting measurements John did. So tried to see if I could find the original post, but have been unable to find any.

The thread is from 1998. Is there any way to look up all posts by Woodgate, so I can track it? (maybe it is posted not on SED)

I found that google groups can in fact filter on author, but did not
find the original post anyway.

Might be hard, since for some reason on google groups, all the posts in
that thread is from 0900 at the same day.

 

[legg]

On Sat, 24 Jun 2023 16:31:22 -0700 (PDT), Klaus Kragelund
<klaus.kragelund@gmail.com> wrote:

Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I found more or less nothing on google. Then I tried the archived SED at google groups, and found a nice thread where John Woodgate has done some work:

https://groups.google.com/g/sci.electronics.design/c/4Aa6TU8E3po/m/oUuAz3pQXksJ

The thread starts with Winfield Hill quoting measurements John did. So tried to see if I could find the original post, but have been unable to find any.

The thread is from 1998. Is there any way to look up all posts by Woodgate, so I can track it? (maybe it is posted not on SED)

Regards

Klaus

There were no \'Google Groups\' in \'98.

Don\'t know what news handler employed \'34BB81EA...\' type
message identification.

The mirrors that lifted threads from usenet are not always
consistent with date and time stamps.

For loss in silicon steel, check with steel vendors.

https://thomas-skinner.com/transformer-laminations/
https://www.amccores.com/pressed-laminations
https://www.jfe-steel.co.jp/en/products/electrical/index.php

RL

 

[Gerhard Hoffmann]

Am 25.06.23 um 18:24 schrieb legg:

On Sat, 24 Jun 2023 16:31:22 -0700 (PDT), Klaus Kragelund
klaus.kragelund@gmail.com> wrote:

Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I found more or less nothing on google. Then I tried the archived SED at google groups, and found a nice thread where John Woodgate has done some work:

https://groups.google.com/g/sci.electronics.design/c/4Aa6TU8E3po/m/oUuAz3pQXksJ

The thread starts with Winfield Hill quoting measurements John did. So tried to see if I could find the original post, but have been unable to find any.

The thread is from 1998. Is there any way to look up all posts by Woodgate, so I can track it? (maybe it is posted not on SED)

Regards

Klaus

There were no \'Google Groups\' in \'98.

Don\'t know what news handler employed \'34BB81EA...\' type
message identification.

The mirrors that lifted threads from usenet are not always
consistent with date and time stamps.

For loss in silicon steel, check with steel vendors.

https://thomas-skinner.com/transformer-laminations/
https://www.amccores.com/pressed-laminations
https://www.jfe-steel.co.jp/en/products/electrical/index.php

RL

J.Woodgate is often on the LTspice list.

Cheers Gerhard

 

[Phil Hobbs]

legg <legg@nospam.magma.ca> wrote:

On Sat, 24 Jun 2023 16:31:22 -0700 (PDT), Klaus Kragelund
klaus.kragelund@gmail.com> wrote:

Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I found more or less nothing on google. Then I tried the archived SED at
google groups, and found a nice thread where John Woodgate has done some work:

https://groups.google.com/g/sci.electronics.design/c/4Aa6TU8E3po/m/oUuAz3pQXksJ

The thread starts with Winfield Hill quoting measurements John did. So
tried to see if I could find the original post, but have been unable to find any.

The thread is from 1998. Is there any way to look up all posts by
Woodgate, so I can track it? (maybe it is posted not on SED)

Regards

Klaus

There were no \'Google Groups\' in \'98.

Don\'t know what news handler employed \'34BB81EA...\' type
message identification.

The mirrors that lifted threads from usenet are not always
consistent with date and time stamps.

For loss in silicon steel, check with steel vendors.

https://thomas-skinner.com/transformer-laminations/
https://www.amccores.com/pressed-laminations
https://www.jfe-steel.co.jp/en/products/electrical/index.php

Google bought the Deja News archive.

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

 

[John Larkin]

On Sun, 25 Jun 2023 18:32:25 +0200, Gerhard Hoffmann <dk4xp@arcor.de>
wrote:

Am 25.06.23 um 18:24 schrieb legg:
On Sat, 24 Jun 2023 16:31:22 -0700 (PDT), Klaus Kragelund
klaus.kragelund@gmail.com> wrote:

Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I found more or less nothing on google. Then I tried the archived SED at google groups, and found a nice thread where John Woodgate has done some work:

https://groups.google.com/g/sci.electronics.design/c/4Aa6TU8E3po/m/oUuAz3pQXksJ

The thread starts with Winfield Hill quoting measurements John did. So tried to see if I could find the original post, but have been unable to find any.

The thread is from 1998. Is there any way to look up all posts by Woodgate, so I can track it? (maybe it is posted not on SED)

Regards

Klaus

There were no \'Google Groups\' in \'98.

Don\'t know what news handler employed \'34BB81EA...\' type
message identification.

The mirrors that lifted threads from usenet are not always
consistent with date and time stamps.

For loss in silicon steel, check with steel vendors.

https://thomas-skinner.com/transformer-laminations/
https://www.amccores.com/pressed-laminations
https://www.jfe-steel.co.jp/en/products/electrical/index.php

RL

J.Woodgate is often on the LTspice list.

Cheers Gerhard

I saw an article by him recently, in EE Times or some such.

 

[legg]

On Sun, 25 Jun 2023 01:56:54 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:

On 25-06-2023 01:31, Klaus Kragelund wrote:
Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I found more or less nothing on google. Then I tried the archived SED at google groups, and found a nice thread where John Woodgate has done some work:

https://groups.google.com/g/sci.electronics.design/c/4Aa6TU8E3po/m/oUuAz3pQXksJ

The thread starts with Winfield Hill quoting measurements John did. So tried to see if I could find the original post, but have been unable to find any.

The thread is from 1998. Is there any way to look up all posts by Woodgate, so I can track it? (maybe it is posted not on SED)


I found that google groups can in fact filter on author, but did not
find the original post anyway.

Might be hard, since for some reason on google groups, all the posts in
that thread is from 0900 at the same day.

The post you\'re referring to had no info on hysteritic core
losses in stepper motors. Mr Woodgate\'s interests have been
in the audio field.

Comments about pre-biasing speakers reflect physical
practicality. Large subwoofers that are excursion-limited,
when pointed at the ground or at the sky can be prebiased
in order to compensate for the static displacement of the cone/
diaphram due to gravity.

Hysterisis loss in that application are a small fraction of
copper loss - and they don\'t tend to use the same type of
steel or magnetic structure as in steppers.

RL

 

[John Larkin]

On Sat, 24 Jun 2023 16:31:22 -0700 (PDT), Klaus Kragelund
<klaus.kragelund@gmail.com> wrote:

Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I would expect them to be small compared to copper loss, and energy
that creates the mechanical output.

Are you full stepping, half, or microstepping? DC or PWM?

 

[Klaus Vestergaard Kragelund]

On 26-06-2023 04:28, John Larkin wrote:

On Sat, 24 Jun 2023 16:31:22 -0700 (PDT), Klaus Kragelund
klaus.kragelund@gmail.com> wrote:

Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I would expect them to be small compared to copper loss, and energy
that creates the mechanical output.

Are you full stepping, half, or microstepping? DC or PWM?

Microstepping, 256 steps.
Just measured the hysteresis loop today. Quite bad, but most motor
laminates are lossy. I have contacted the manufactor to get the data for
the laminate and the turns quantity, then it\'s simple to check with a
calculation.

It\'s also possible to measure the loss with an impedance analyzer, but
that process is hard.

 

[John Larkin]

On Tue, 27 Jun 2023 00:20:21 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:

On 26-06-2023 04:28, John Larkin wrote:
On Sat, 24 Jun 2023 16:31:22 -0700 (PDT), Klaus Kragelund
klaus.kragelund@gmail.com> wrote:

Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I would expect them to be small compared to copper loss, and energy
that creates the mechanical output.

Are you full stepping, half, or microstepping? DC or PWM?


Microstepping, 256 steps.
Just measured the hysteresis loop today. Quite bad, but most motor
laminates are lossy. I have contacted the manufactor to get the data for
the laminate and the turns quantity, then it\'s simple to check with a
calculation.

It\'s also possible to measure the loss with an impedance analyzer, but
that process is hard.

You can apply sin/cos weighted high-frequency PWM drives to the
stepper windings, and let them fiter it. Or use some external
inductors so the motor lams don\'t see the PWM and have corresponding
losses.

When the motor is not moving, one can reduce the drives and save some
power, with maybe a tiny angular error at the transition.

 

[Klaus Vestergaard Kragelund]

On 26-06-2023 03:09, legg wrote:

On Sun, 25 Jun 2023 01:56:54 +0200, Klaus Vestergaard Kragelund
klauskvik@hotmail.com> wrote:

On 25-06-2023 01:31, Klaus Kragelund wrote:
Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I found more or less nothing on google. Then I tried the archived SED at google groups, and found a nice thread where John Woodgate has done some work:

https://groups.google.com/g/sci.electronics.design/c/4Aa6TU8E3po/m/oUuAz3pQXksJ

The thread starts with Winfield Hill quoting measurements John did. So tried to see if I could find the original post, but have been unable to find any.

The thread is from 1998. Is there any way to look up all posts by Woodgate, so I can track it? (maybe it is posted not on SED)


I found that google groups can in fact filter on author, but did not
find the original post anyway.

Might be hard, since for some reason on google groups, all the posts in
that thread is from 0900 at the same day.

The post you\'re referring to had no info on hysteritic core
losses in stepper motors. Mr Woodgate\'s interests have been
in the audio field.

Comments about pre-biasing speakers reflect physical
practicality. Large subwoofers that are excursion-limited,
when pointed at the ground or at the sky can be prebiased
in order to compensate for the static displacement of the cone/
diaphram due to gravity.

Hysterisis loss in that application are a small fraction of
copper loss - and they don\'t tend to use the same type of
steel or magnetic structure as in steppers.

Yes, I know it was for another application. But the general idea, how to
measure the properties is the same.

 

[Klaus Vestergaard Kragelund]

On 27-06-2023 03:30, John Larkin wrote:

On Tue, 27 Jun 2023 00:20:21 +0200, Klaus Vestergaard Kragelund
klauskvik@hotmail.com> wrote:

On 26-06-2023 04:28, John Larkin wrote:
On Sat, 24 Jun 2023 16:31:22 -0700 (PDT), Klaus Kragelund
klaus.kragelund@gmail.com> wrote:

Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I would expect them to be small compared to copper loss, and energy
that creates the mechanical output.

Are you full stepping, half, or microstepping? DC or PWM?


Microstepping, 256 steps.
Just measured the hysteresis loop today. Quite bad, but most motor
laminates are lossy. I have contacted the manufactor to get the data for
the laminate and the turns quantity, then it\'s simple to check with a
calculation.

It\'s also possible to measure the loss with an impedance analyzer, but
that process is hard.

You can apply sin/cos weighted high-frequency PWM drives to the
stepper windings, and let them fiter it. Or use some external
inductors so the motor lams don\'t see the PWM and have corresponding
losses.

Yes, I have seen that done on GaN motor drives, but in that case it was
done to reduce the dV/dt that would otherwise damage the insulation of
the enameled wire

When the motor is not moving, one can reduce the drives and save some
power, with maybe a tiny angular error at the transition.

In this application, there is a linear thread attached, so during
standstill the motor is powerless

 

[legg]

On Tue, 27 Jun 2023 00:20:21 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:

On 26-06-2023 04:28, John Larkin wrote:
On Sat, 24 Jun 2023 16:31:22 -0700 (PDT), Klaus Kragelund
klaus.kragelund@gmail.com> wrote:

Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I would expect them to be small compared to copper loss, and energy
that creates the mechanical output.

Are you full stepping, half, or microstepping? DC or PWM?


Microstepping, 256 steps.
Just measured the hysteresis loop today. Quite bad, but most motor
laminates are lossy. I have contacted the manufactor to get the data for
the laminate and the turns quantity, then it\'s simple to check with a
calculation.

It\'s also possible to measure the loss with an impedance analyzer, but
that process is hard.

The frequency\'s got to be pretty low, though; isn\'t it just the step
rate? Otherwise it\'s DC.

RL

 

[Klaus Vestergaard Kragelund]

On 27-06-2023 17:00, legg wrote:

On Tue, 27 Jun 2023 00:20:21 +0200, Klaus Vestergaard Kragelund
klauskvik@hotmail.com> wrote:

On 26-06-2023 04:28, John Larkin wrote:
On Sat, 24 Jun 2023 16:31:22 -0700 (PDT), Klaus Kragelund
klaus.kragelund@gmail.com> wrote:

Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I would expect them to be small compared to copper loss, and energy
that creates the mechanical output.

Are you full stepping, half, or microstepping? DC or PWM?


Microstepping, 256 steps.
Just measured the hysteresis loop today. Quite bad, but most motor
laminates are lossy. I have contacted the manufactor to get the data for
the laminate and the turns quantity, then it\'s simple to check with a
calculation.

It\'s also possible to measure the loss with an impedance analyzer, but
that process is hard.

The frequency\'s got to be pretty low, though; isn\'t it just the step
rate? Otherwise it\'s DC.

The frequency is 25kHz. The stepper driver drives the current into the
coil as a hysteretic buck converter, where the current demand signal to
the buck converter is set by the sine lookup table incremented by the
Step input.

A plot is seen here:

https://www.electronicsdesign.dk/tmp/StepperSIgnals.pdf

 

[legg]

On Tue, 27 Jun 2023 20:41:24 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:

On 27-06-2023 17:00, legg wrote:
On Tue, 27 Jun 2023 00:20:21 +0200, Klaus Vestergaard Kragelund
klauskvik@hotmail.com> wrote:

On 26-06-2023 04:28, John Larkin wrote:
On Sat, 24 Jun 2023 16:31:22 -0700 (PDT), Klaus Kragelund
klaus.kragelund@gmail.com> wrote:

Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I would expect them to be small compared to copper loss, and energy
that creates the mechanical output.

Are you full stepping, half, or microstepping? DC or PWM?


Microstepping, 256 steps.
Just measured the hysteresis loop today. Quite bad, but most motor
laminates are lossy. I have contacted the manufactor to get the data for
the laminate and the turns quantity, then it\'s simple to check with a
calculation.

It\'s also possible to measure the loss with an impedance analyzer, but
that process is hard.

The frequency\'s got to be pretty low, though; isn\'t it just the step
rate? Otherwise it\'s DC.

The frequency is 25kHz. The stepper driver drives the current into the
coil as a hysteretic buck converter, where the current demand signal to
the buck converter is set by the sine lookup table incremented by the
Step input.

A plot is seen here:

https://www.electronicsdesign.dk/tmp/StepperSIgnals.pdf

If the pwm is continuous, then hysterisis loss will be hard
to calculate, as it varies the farther you are out from 0 and
is non-loop (ie a spiral) so long as the average is changing.

Under steady state, around zero, loss is related to the area
of the loop. Published Steinmetz coefficients only apply in
that region.

RL

 

[Klaus Vestergaard Kragelund]

On 28-06-2023 00:16, legg wrote:

On Tue, 27 Jun 2023 20:41:24 +0200, Klaus Vestergaard Kragelund
klauskvik@hotmail.com> wrote:

On 27-06-2023 17:00, legg wrote:
On Tue, 27 Jun 2023 00:20:21 +0200, Klaus Vestergaard Kragelund
klauskvik@hotmail.com> wrote:

On 26-06-2023 04:28, John Larkin wrote:
On Sat, 24 Jun 2023 16:31:22 -0700 (PDT), Klaus Kragelund
klaus.kragelund@gmail.com> wrote:

Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I would expect them to be small compared to copper loss, and energy
that creates the mechanical output.

Are you full stepping, half, or microstepping? DC or PWM?


Microstepping, 256 steps.
Just measured the hysteresis loop today. Quite bad, but most motor
laminates are lossy. I have contacted the manufactor to get the data for
the laminate and the turns quantity, then it\'s simple to check with a
calculation.

It\'s also possible to measure the loss with an impedance analyzer, but
that process is hard.

The frequency\'s got to be pretty low, though; isn\'t it just the step
rate? Otherwise it\'s DC.

The frequency is 25kHz. The stepper driver drives the current into the
coil as a hysteretic buck converter, where the current demand signal to
the buck converter is set by the sine lookup table incremented by the
Step input.

A plot is seen here:

https://www.electronicsdesign.dk/tmp/StepperSIgnals.pdf


If the pwm is continuous, then hysterisis loss will be hard
to calculate, as it varies the farther you are out from 0 and
is non-loop (ie a spiral) so long as the average is changing.

Yes, it will vary some depending on how far it is driving up on the BH
curve.

Under steady state, around zero, loss is related to the area
of the loop. Published Steinmetz coefficients only apply in
that region.

Measurement of the curve is seen here, compared to a ferrite drum core
inductor.

https://www.electronicsdesign.dk/tmp/Stepper_hyst_curve.pdf

 

[legg]

On Wed, 28 Jun 2023 01:46:07 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:

On 28-06-2023 00:16, legg wrote:
On Tue, 27 Jun 2023 20:41:24 +0200, Klaus Vestergaard Kragelund
klauskvik@hotmail.com> wrote:

On 27-06-2023 17:00, legg wrote:
On Tue, 27 Jun 2023 00:20:21 +0200, Klaus Vestergaard Kragelund
klauskvik@hotmail.com> wrote:

On 26-06-2023 04:28, John Larkin wrote:
On Sat, 24 Jun 2023 16:31:22 -0700 (PDT), Klaus Kragelund
klaus.kragelund@gmail.com> wrote:

Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I would expect them to be small compared to copper loss, and energy
that creates the mechanical output.

Are you full stepping, half, or microstepping? DC or PWM?


Microstepping, 256 steps.
Just measured the hysteresis loop today. Quite bad, but most motor
laminates are lossy. I have contacted the manufactor to get the data for
the laminate and the turns quantity, then it\'s simple to check with a
calculation.

It\'s also possible to measure the loss with an impedance analyzer, but
that process is hard.

The frequency\'s got to be pretty low, though; isn\'t it just the step
rate? Otherwise it\'s DC.

The frequency is 25kHz. The stepper driver drives the current into the
coil as a hysteretic buck converter, where the current demand signal to
the buck converter is set by the sine lookup table incremented by the
Step input.

A plot is seen here:

https://www.electronicsdesign.dk/tmp/StepperSIgnals.pdf


If the pwm is continuous, then hysterisis loss will be hard
to calculate, as it varies the farther you are out from 0 and
is non-loop (ie a spiral) so long as the average is changing.

Yes, it will vary some depending on how far it is driving up on the BH
curve.


Under steady state, around zero, loss is related to the area
of the loop. Published Steinmetz coefficients only apply in
that region.

Measurement of the curve is seen here, compared to a ferrite drum core
inductor.

https://www.electronicsdesign.dk/tmp/Stepper_hyst_curve.pdf

If you say so.

At best, this comparison shows the limitations in your present
measurement and data processing technique.

There are two orders of magnitude difference in the units
employed for \'comparison\'.

RL

 

[Klaus Kragelund]

On Wednesday, 28 June 2023 at 16:24:46 UTC+2, legg wrote:

On Wed, 28 Jun 2023 01:46:07 +0200, Klaus Vestergaard Kragelund
klau...@hotmail.com> wrote:

On 28-06-2023 00:16, legg wrote:
On Tue, 27 Jun 2023 20:41:24 +0200, Klaus Vestergaard Kragelund
klau...@hotmail.com> wrote:

On 27-06-2023 17:00, legg wrote:
On Tue, 27 Jun 2023 00:20:21 +0200, Klaus Vestergaard Kragelund
klau...@hotmail.com> wrote:

On 26-06-2023 04:28, John Larkin wrote:
On Sat, 24 Jun 2023 16:31:22 -0700 (PDT), Klaus Kragelund
klaus.k...@gmail.com> wrote:

Hi

I am looking into losses of a stepper motor, specifically hysteresis loss.

I would expect them to be small compared to copper loss, and energy
that creates the mechanical output.

Are you full stepping, half, or microstepping? DC or PWM?


Microstepping, 256 steps.
Just measured the hysteresis loop today. Quite bad, but most motor
laminates are lossy. I have contacted the manufactor to get the data for
the laminate and the turns quantity, then it\'s simple to check with a
calculation.

It\'s also possible to measure the loss with an impedance analyzer, but
that process is hard.

The frequency\'s got to be pretty low, though; isn\'t it just the step
rate? Otherwise it\'s DC.

The frequency is 25kHz. The stepper driver drives the current into the
coil as a hysteretic buck converter, where the current demand signal to
the buck converter is set by the sine lookup table incremented by the
Step input.

A plot is seen here:

https://www.electronicsdesign.dk/tmp/StepperSIgnals.pdf


If the pwm is continuous, then hysterisis loss will be hard
to calculate, as it varies the farther you are out from 0 and
is non-loop (ie a spiral) so long as the average is changing.

Yes, it will vary some depending on how far it is driving up on the BH
curve.


Under steady state, around zero, loss is related to the area
of the loop. Published Steinmetz coefficients only apply in
that region.

Measurement of the curve is seen here, compared to a ferrite drum core
inductor.

https://www.electronicsdesign.dk/tmp/Stepper_hyst_curve.pdf

If you say so.

At best, this comparison shows the limitations in your present
measurement and data processing technique.

Yeah, crappy 12bit picoscope. In fact, I have pretty expensive Siglent and Tek scopes, but the Picoscope SW has good math functions, so I find myself using that for more complex work. If I had time, I should build a real integrator.

There are two orders of magnitude difference in the units
employed for \'comparison\'.

Yes. Two different components. 6mH winding vs 100uH drum.

The real comparison is looking at the hysteresis area, much lower for the ferrite, which is should be, since ferrite is way better than laminated iron.

 

[legg]

On Wed, 28 Jun 2023 15:18:37 -0700 (PDT), Klaus Kragelund
<klaus.kragelund@gmail.com> wrote:

<snip>

The frequency\'s got to be pretty low, though; isn\'t it just the step
rate? Otherwise it\'s DC.

The frequency is 25kHz. The stepper driver drives the current into the
coil as a hysteretic buck converter, where the current demand signal to
the buck converter is set by the sine lookup table incremented by the
Step input.

A plot is seen here:

https://www.electronicsdesign.dk/tmp/StepperSIgnals.pdf


If the pwm is continuous, then hysterisis loss will be hard
to calculate, as it varies the farther you are out from 0 and
is non-loop (ie a spiral) so long as the average is changing.

Yes, it will vary some depending on how far it is driving up on the BH
curve.


Under steady state, around zero, loss is related to the area
of the loop. Published Steinmetz coefficients only apply in
that region.

Measurement of the curve is seen here, compared to a ferrite drum core
inductor.

https://www.electronicsdesign.dk/tmp/Stepper_hyst_curve.pdf

If you say so.

At best, this comparison shows the limitations in your present
measurement and data processing technique.


Yeah, crappy 12bit picoscope. In fact, I have pretty expensive Siglent and Tek scopes, but the Picoscope SW has good math functions, so I find myself using that for more complex work. If I had time, I should build a real integrator.

There are two orders of magnitude difference in the units
employed for \'comparison\'.

Yes. Two different components. 6mH winding vs 100uH drum.

The real comparison is looking at the hysteresis area, much lower for the ferrite, which is should be, since ferrite is way better than laminated iron.

Even so, ferrite will exhibit a loop, not something that crosses over
itself a couple of times in the sweep.

At 20Vpk, reversing at 20KHz, I don\'t see a 6mH choke exhibiting much
loss, no matter what the material. With steppers, it\'s usually the
copper that dominates, because it costs more by weight/volume.

Sinusoidal exitation is only intended to reduce mechanical noise -
HF pwm to reduce losses in generation of the sinusoidal form or
moderate the static torque / power loss.

RL

 

[Klaus Vestergaard Kragelund]

On 29-06-2023 14:04, legg wrote:

On Wed, 28 Jun 2023 15:18:37 -0700 (PDT), Klaus Kragelund
klaus.kragelund@gmail.com> wrote:

snip
The frequency\'s got to be pretty low, though; isn\'t it just the step
rate? Otherwise it\'s DC.

The frequency is 25kHz. The stepper driver drives the current into the
coil as a hysteretic buck converter, where the current demand signal to
the buck converter is set by the sine lookup table incremented by the
Step input.

A plot is seen here:

https://www.electronicsdesign.dk/tmp/StepperSIgnals.pdf


If the pwm is continuous, then hysterisis loss will be hard
to calculate, as it varies the farther you are out from 0 and
is non-loop (ie a spiral) so long as the average is changing.

Yes, it will vary some depending on how far it is driving up on the BH
curve.


Under steady state, around zero, loss is related to the area
of the loop. Published Steinmetz coefficients only apply in
that region.

Measurement of the curve is seen here, compared to a ferrite drum core
inductor.

https://www.electronicsdesign.dk/tmp/Stepper_hyst_curve.pdf

If you say so.

At best, this comparison shows the limitations in your present
measurement and data processing technique.


Yeah, crappy 12bit picoscope. In fact, I have pretty expensive Siglent and Tek scopes, but the Picoscope SW has good math functions, so I find myself using that for more complex work. If I had time, I should build a real integrator.

There are two orders of magnitude difference in the units
employed for \'comparison\'.

Yes. Two different components. 6mH winding vs 100uH drum.

The real comparison is looking at the hysteresis area, much lower for the ferrite, which is should be, since ferrite is way better than laminated iron.

Even so, ferrite will exhibit a loop, not something that crosses over
itself a couple of times in the sweep.

At 20Vpk, reversing at 20KHz, I don\'t see a 6mH choke exhibiting much
loss, no matter what the material. With steppers, it\'s usually the
copper that dominates, because it costs more by weight/volume.

Yes, I think you are right. I will try to get the data, to calculate the
loss.

Sinusoidal exitation is only intended to reduce mechanical noise -
HF pwm to reduce losses in generation of the sinusoidal form or
moderate the static torque / power loss.

Also intended to provide high step reolution..