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Correct waveform for powerSTEP01 phase current

Question asked by mouser on Jan 31, 2018
Latest reply on Feb 9, 2018 by mouser



I'm using IHMOA03 to control NEMA23 format stepper motor running in half-step current controlled clock step mode. I put the scope on the sense resistor R1 to monitor the phase current and it is not what I expected.


The motor is a six wire connection with the centre taps left unconnected: series full coil connection.


The pulse rate is circa 1kHz and vertical scale is 0.2V/div ( R1 is 0R1 ) .  The wave is smoothed because R/L corresponds to about 625Hz ( 1 ohm / 1.6mH )  that's fine but I was expecting a symmetric waveform not this abrupt cut off. 


Each winding should go through a cycle 0 70 100 70 0 -70 -100 -70 0 % ; ie a symmetrical cycle. Why am I not seeing this?


Slower speeds show the step nature but there is still this asymmetric switching. What is this about?