## Stepper motor maximum flux linkage

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Not sure if the method I am using to extract the maximum flux linkage between the rotor and stator of a stepper motor is correct.

The flux linkage between stator and rotor can be described by a sinusoidal function with magnitude equal to the maximum flux linkage. The flux linkage between phase A and the rotor is:

p is the number of rotor teeth of the stepper motor and theta is the rotor angle. ΨM is the constant of the motor I am trying to calculate - the maximum flux linkage.

The voltage induced to a phase of the motor then can be calculated as the rate of change of the flux linkages. E.g. for the phase A of the motor:

I am using a second motor to turn the stepper motor at a fixed speed and I attach my oscilloscope probes at one of the stepper motor phases.

The oscilloscope shows a sinusoidal voltage signal. By measuring the period I am able to determine the rotational speed.

After that by measuring the signal's peak I determine the maximum flux linkage by using the equation: ΨΜ=(signal's peak in volts)/(rotational speed)/(number of stepper motor rotor teeth-p)

This subject is out of my domain, I am not 100% sure of this calculation. Any help would be greatly appreciated.

TO THE FINDER... THE ISLE OF KOHOLINT, IS BUT AN ILLUSION... HUMAN, MONSTER, SEA, SKY... A SCENE ON THE LID OF A SLEEPER'S EYE... AWAKE THE DREAMER, AND KOHOLINT WILL VANISH MUCH LIKE A BUBBLE ON A NEEDLE... CAST-AWAY, YOU SHOULD KNOW THE TRUTH!

I am using a second motor to turn the stepper motor at a fixed speed ...how do you know the speed is perfectly steady?   Or  are you going from your 'oscope?

Seems like you are on the right track...search for Leenhouts (stepper author) for lots of good stepper info.

What are you going to do with the flux linage anyhow?

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

I am using it to simulate the motor in Matlab-Simulink.

The second motor I am using is a hand drill so the speed won't be 100% steady but it's the best I can do for now.

Still I think I should be able to extract a good approximation of this constant even by having a slightly oscillatory speed.

If the speed is very unstable it shows in the waveform - the frequency of the waveform changes accordingly to the rotational speed.

Thank you, I will look for his work!

I found this book where a procedure is followed to extract that maximum flux linkage constant.

Unfortunately it is not very clear to me what the method is and it is not described in detail.

The method is in page 25:

http://publications.lib.chalmers.se/records/fulltext/255699/255699.pdf

By using the method I wrote in the previous post and using the waveform and speed that was used in the book I am not coming up with the same number for the flux linkage the author does!

I feel I am missing something and that is the reason I posted here.

TO THE FINDER... THE ISLE OF KOHOLINT, IS BUT AN ILLUSION... HUMAN, MONSTER, SEA, SKY... A SCENE ON THE LID OF A SLEEPER'S EYE... AWAKE THE DREAMER, AND KOHOLINT WILL VANISH MUCH LIKE A BUBBLE ON A NEEDLE... CAST-AWAY, YOU SHOULD KNOW THE TRUTH!