I have a question regarding frequency and inductance. What is the relation between frequency of an applied voltage that is square wave, over an inductor, and the average current that would flow through it? Is there a way to calculate it using analitic equations? I am working on a motor application for university. I applied 5kHz pwm voltage over my motor windings and i couldnt stand the noise, because 5k is in the hearing range. So i applied higher frequency. I noticed that with higher frequency, the average current flowing through windings started to increase. I know we should not try to analyze impedance here as it is a square wave. Why does the current grow with increasing square wave frequency? I would apreciate all help.

  • \$\begingroup\$ You should analyze each pulse as DC with initial conditions left from the transition. You can assume the steady state (the initial conditions are the same for each period) \$\endgroup\$ – Eugene Sh. Mar 14 '16 at 18:14
  • \$\begingroup\$ Do you suggest that the current through coil arises faster than it falls and thus the average current is high? \$\endgroup\$ – Bremen Mar 14 '16 at 18:16
  • \$\begingroup\$ I am just suggesting the way to analyze the behavior. Similar to this, but for inductor. \$\endgroup\$ – Eugene Sh. Mar 14 '16 at 18:18
  • \$\begingroup\$ How are you measuring the inductor current? Do you know the SRF of your inductor? \$\endgroup\$ – The Photon Mar 14 '16 at 19:08
  • \$\begingroup\$ I see the aproximate current on the labolatory ac adapter. It has build in amper meter. This is the motor datasheet dropbox.com/s/kgr0o6kekp0m3cd/ST4118L3004-A.pdf?dl=0 \$\endgroup\$ – Bremen Mar 14 '16 at 19:12

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