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Author Topic: Stepper Motor Phase Shift and Speedup,,,,  (Read 1466 times)

Offline floodrod

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Stepper Motor Phase Shift and Speedup,,,,
« on: November 23, 2022, 02:54:04 AM »
Getting a little excited here, but also a little stumped... But I can show true and repeatable 90 degree phase shift with speedup on load.
 Two setups comparing...

SETUP 1:

Small DC motor driving a Nema23 stepper with a belt as a generator..  Generator outputs go to step down transformer (120 to 24v)  but reverse so it steps up.
Run motor- record RPM and input amps.  Now add resistor load (or direct short) to secondary....  , Input amperage goes down very noticeably and RPM increase substantially while pulling a load...   View on 2 channel scope..  1 channel connected to stepper output leads.  Channel 2 connected to transformer secondary..   We see the sines perfectly shifted 90 degrees as we want when loaded..  See Pics Below!

(Note- I can make the effect happen with several different configurations)

SETUP 2:

Exact same setup but with a regular pulse motor..  2 collecting coils going into the exact same transformer..  Now the effect is GONE!  Add load to the secondary, and phases are normal..  Putting load on secondary slows the rotor...  DOAH....

Why can I get this effect with a belt-driven stepper as a generator but not with the pulse motor?  This phase shift is exactly what I am looking for...  I really wish it worked on my pulse motor thats much easier to turn with very little input..

 

Offline floodrod

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Re: Stepper Motor Phase Shift and Speedup,,,,
« Reply #1 on: November 23, 2022, 03:00:34 AM »
Forgot to say-  on the stepper I am only using 1 pair of leads..  The other pair is not connected..  I will test that variable in a little while if the effect still happens when both generator coils in the stepper are in series.. 

Offline floodrod

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Re: Stepper Motor Phase Shift and Speedup,,,,
« Reply #2 on: November 23, 2022, 03:33:21 AM »
Tested wiring both sets of generator leads in series..  and YES the effect works like a charm, even better...

HERE is a Video of the effect-  https://www.youtube.com/watch?v=NUB2yY_PNFU


Offline floodrod

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Re: Stepper Motor Phase Shift and Speedup,,,,
« Reply #3 on: November 24, 2022, 12:35:06 AM »
Load tests have been done today.

Measuring amperage going through the 8 ohm resistor powered from the secondary..  RPM goes up and input goes down as you saw in the video..  Then it stays there..
When I increase input from the supply, RPM goes us (as expected)  but output amperage across the resistor goes DOWN as more input is put in..

When I remove the transformer, everything acts normal again..  Connecting a load bogs the motor to a crawl and input goes up as expected..

Trying to wrap my head around it all, and what to test next.

Offline citfta

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Re: Stepper Motor Phase Shift and Speedup,,,,
« Reply #4 on: November 24, 2022, 04:13:33 PM »
Hi floodrod.


As it looks like no one else is going to respond and I have a few minutes I will try to help you understand what you are seeing.  First thing is there is not enough information to make a definite conclusion to what you are seeing so some of what I am going to suggest is only based on what I see.  You don't show the frequency of the signal coming from the stepper motor.  But from what I see I believe it is probably much higher than 60 hz.  Also what I see on your scope is that the speed of the stepper motor is in fact slowing down under load NOT speeding up.  I believe the scope you are using should be able to show the frequency of the signal at the top of the screen but I couldn't read that from the video or you may not have that function turned on.  But looking at just the signal coming from the stepper motor if you watch it under load you will see that the distance on the scope where the signal crosses the zero line gets longer under load.  In other words under load it takes longer for the signal to cross the zero line than it does when not under load.  This means the frequency is lower which also means the stepper motor is in fact actually turning slower.  The louder sound under load may be causing you to think it is speeding up under load but the scope signal is showing the opposite.


Transformers are designed to operate most efficiently at certain frequencies.  When you get pretty far away from that frequency then the efficiency drops. I think what you are seeing is that at the speed you are driving the stepper motor you are beyond the range of efficient frequency for that transformer.  When you add the load that is slowing down the stepper motor and thus the frequency which is allowing the transformer to operate a little more efficiently so thus your output voltage goes up.  And when you increase your input as you said the output drops and that again is because the frequency has gone even farther from the best frequency for that transformer.  If you were to calculate the input power and compare it to the output power I think you will find that using the transformer that way is not efficient at all.  I hope this helps you understand what you are seeing.


Keep experimenting!  That is the very best way to learn!


Take care,
Carroll

Offline floodrod

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Re: Stepper Motor Phase Shift and Speedup,,,,
« Reply #5 on: November 24, 2022, 04:51:15 PM »
Hi floodrod.


As it looks like no one else is going to respond and I have a few minutes I will try to help you understand what you are seeing.  First thing is there is not enough information to make a definite conclusion to what you are seeing so some of what I am going to suggest is only based on what I see.  You don't show the frequency of the signal coming from the stepper motor.  But from what I see I believe it is probably much higher than 60 hz.  Also what I see on your scope is that the speed of the stepper motor is in fact slowing down under load NOT speeding up.  I believe the scope you are using should be able to show the frequency of the signal at the top of the screen but I couldn't read that from the video or you may not have that function turned on.  But looking at just the signal coming from the stepper motor if you watch it under load you will see that the distance on the scope where the signal crosses the zero line gets longer under load.  In other words under load it takes longer for the signal to cross the zero line than it does when not under load.  This means the frequency is lower which also means the stepper motor is in fact actually turning slower.  The louder sound under load may be causing you to think it is speeding up under load but the scope signal is showing the opposite.


Transformers are designed to operate most efficiently at certain frequencies.  When you get pretty far away from that frequency then the efficiency drops. I think what you are seeing is that at the speed you are driving the stepper motor you are beyond the range of efficient frequency for that transformer.  When you add the load that is slowing down the stepper motor and thus the frequency which is allowing the transformer to operate a little more efficiently so thus your output voltage goes up.  And when you increase your input as you said the output drops and that again is because the frequency has gone even farther from the best frequency for that transformer.  If you were to calculate the input power and compare it to the output power I think you will find that using the transformer that way is not efficient at all.  I hope this helps you understand what you are seeing.


Keep experimenting!  That is the very best way to learn!


Take care,
Carroll

The speed goes up when pulling a load.  And by a big margin at that.  Amps go down as speed increases.  No doubt about that.. 

Take away the transformer then speed goes down while pulling a load.


If you watch the video again= frequency on the scope is visible...  1.3 khz not loaded..  2.1 khz loaded

Offline Tarsier_79

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Re: Stepper Motor Phase Shift and Speedup,,,,
« Reply #6 on: November 24, 2022, 08:33:51 PM »
It looks like you have no feedback going back to the input, so it doesn't make sense to me. I would think any motor should act the same at the same speed. I guess you would need a smaller load on the pulse motor as they are not as powerful as a normal motor, but that might not be a big enough load on the transformer for the effect to occur?

What is the model of the drive motor you are using? and what voltage are you supplying it?

The transformer under load is around 4.7V P-P (3.32V P-P). Current is 0.415A across 8 Ohm, 1.38W. Not huge, but you wouldn't expect much from a stepper.

Try adding the same load directly to the stepper, (1.38W). I imagine you will need a lower value resistor, try a 0.3 Ohm (expecting 0.66V out from your stepper under load).

You could also try adding a physical load to the motor with the end of a screwdriver or similar.

Offline stivep

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Re: Stepper Motor Phase Shift and Speedup,,,,
« Reply #7 on: November 24, 2022, 09:12:41 PM »
SETUP 1:
1 channel connected to stepper output leads.  Channel 2 connected to transformer secondary..   We see the sines perfectly shifted 90 degrees as we want when loaded..  See
FNIRSI-1014D
SETUP 1: transformer is serving as of the step up transformer
-channel 2 connected to primary ( thin wire
-channel 1 connected to? where?
Fluke 26 III is measuring :
-"input current" - (that's the proper  wording)
 (used by you " input amp's" - wording is incorrect )

________________________________________________
Points of concern:

1.
https://youtu.be/lineu9C9kq4?t=73

2. FNIRSI-1014D Product Manual
https://www.rcscomponents.kiev.ua/datasheets/fnirsi-1014d%20product_manual.pdf
warning: when the two channels are used at the same time the ground clamps of the two probes must be connected together is strictly forbidden to connect to the ground
2a. https://youtu.be/jfF_vGSyqW4?t=88
-no collaboration for the probes.

3. The video is absolutely not clear in : what is connected were.?
4. the expected explanation, raising even more questions in mind of an observer.
- what do you need transformer for?
- why can't you make the same without transformer?
- what is the channel number 1 of the oscilloscope connected to?
- why in minute  1:37  channel number 1 shows 37  kilohertz?
- why in minute  1:40  channel number 1 shows 2.14kHz?
- Because channel number 2 connection is not shown, we can't determine whether you are measuring
   Voltage or current, but there is significant sinusoidal signal change when you are connecting the load.
  what is the value change?

_________________________________________

Things to do:

- The transformer is not air transformer, please connect generator there is built into
Your scope  FNIRSI-1014D.
-connect the primary ( that thick wire) to generator.
- Connect secondary ( that thin wire) to channel 1 of your oscilloscope.
- Change the frequency from 0 kHz to 50 kHz using sinusoidal signal,
   then repeat it again with square-shaped signal while looking
   for distortion of the shape in both cases


Transformers are designed to operate most efficiently at certain frequencies.
Carroll
Carroll was right. transformers with core have a limit of frequency operation.

conclusions:
the video and the material is in this form is completely not acceptable
for any kind of scientific or technical analysis by professionals.
I'm not trying to criticize you nor take sides, I just cannot make any logical conclusions.

Many of us are preoccupied with their daily activities and it took me
over two hours which not everybody is going to dedicate for such analysis.

the picture from below shows which part of the screen is responsible for channel number one and channel number two.
The yellow  color is input number one and blue color is input number two.
This will help you to better understand what's going on in the video.
HERE is a Video of the effect-  https://www.youtube.com/watch?v=NUB2yY_PNFU

keep experimenting
 Wesley
« Last Edit: November 25, 2022, 12:30:27 AM by stivep »

Offline floodrod

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Re: Stepper Motor Phase Shift and Speedup,,,,
« Reply #8 on: November 25, 2022, 02:27:42 AM »
...
 

Offline floodrod

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Re: Stepper Motor Phase Shift and Speedup,,,,
« Reply #9 on: November 25, 2022, 02:54:33 AM »

___

Offline floodrod

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Re: Stepper Motor Phase Shift and Speedup,,,,
« Reply #10 on: November 25, 2022, 03:23:15 AM »
Editing....

Offline Tarsier_79

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Re: Stepper Motor Phase Shift and Speedup,,,,
« Reply #11 on: November 25, 2022, 03:46:12 AM »
Quote
-channel 1 connected to? where?

I thought it was pretty clear where it was connected to.

Quote
warning: when the two channels are used at the same time the ground clamps of the two probes must be connected together is strictly forbidden to connect to the ground

If you understand how a transformer and an oscilloscope works, you would understand that it is connected properly.

Quote
-no collaboration for the probes.
Quote
the video and the material is in this form is completely not acceptable
for any kind of scientific or technical analysis by professionals.

Where are the professionals?
The video is fine. It explains perfectly how it is set up then shows the anomaly.

ADD: This is one of the most interesting videos I have seen on this site. Thank you Flood.

Offline floodrod

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Re: Stepper Motor Phase Shift and Speedup,,,,
« Reply #12 on: November 25, 2022, 05:02:30 AM »
Thanks TAR,

But I do appreciate Seip's comments as they made me retest and come to a new conclusion.  The stepper has nothing to do with it..  The transformers themselves are responsible for this..  The stepper just puts out much higher frequencies that any generator I can make.. (unless I use like 400 poles)..

In the past I did test these transformers for resonant frequency, and open circuit they resonate at 227 KHz (estimate)..  But after Seip's comments, I whipped the signal generator out and when loaded with a resistor on the secondary- the magic phase shift occurs at about 2 KHz. 

When I rectify the secondary and connect it to a 6V lead acid battery, the phase shift occurs somewhere around 4 KHz. (but it varies with amplitude input)..

Still it's in the right direction because I was able to see how the phase shift actually can take real physical work load off the source, the motor spins quicker loaded than unloaded with less input power.

I'm a newbie, I will fully admit that..  But today I learned an important lesson..  Resonance frequency and phase shift change depend on what load you use.  Open circuit frequencies mean little..

Not sure if these doors will lead anywhere- but I have ideas I need to test

Offline Tarsier_79

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Re: Stepper Motor Phase Shift and Speedup,,,,
« Reply #13 on: November 25, 2022, 05:38:44 AM »
That is great! You have isolated the exact cause of what you saw.

Transformers are usually pretty efficient. I am not sure what the effects of the phase shift you are getting are going to be on that. Although is probably more likely the transformer is putting a load on the system even though the output is open at that frequency, it will be interesting to see if that is not the case.

I am looking forward to seeing more. Good luck.

Online ramset

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Re: Stepper Motor Phase Shift and Speedup,,,,
« Reply #14 on: November 25, 2022, 11:42:59 AM »
  I was told A thermometer is a useful tool for speed up under load claims,
Transformers are designed for specific applications with design windows …
If used outside these applications it will not perform well( get hot etc) or transfer less than optimal flow !
Then as it approaches it’s design criteria… it will cool down and flow ( transform..)
More  efficiently !( things which are down stream would benefit from this ( speed etc)


  A design engineer explained this to me years back when asking about Thane Heinz and David Bowling
Speed up under load claims , he also told me this was a method used for speed control in some applications ( said he had an electric yard tractor which used this method? ( seemed wasteful to me
In a battery powered system??




Carroll pointed to this also  ( I believe)


Just passing along one possible cause which I was taught by member ION (Vortex 1 TPU researcher here)
Respectfully
Chet K