Current sampling of dc motor for closed loop control.

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seyyah

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I'm tring to control a brushed dc motor which is 24V, 200W in a closed loop manner. I've confused in the inner current loop section. The current is not steady as shown in the attachment. What should I do here? Get the average or peak value or something else? Thanks.
 

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Average current is probably what you want to control, but slows down the loop which has to consider the average filter delay. Peak current control gives fastest response and direct overcurrent protection, but needs slope compensation to achieve stability and also a correction for Ipk/Iavg ratio.

A higher pwm frequency reduces the Irms related winding losses.
 
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    seyyah

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Hi,
You can use either. Average current mode control will control it at the average value whereas peak current mode control will control it at the peak value.
 
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    seyyah

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Average current calculation will be better in speed control of DC machines, but then again it is totally dependent over the requirements of the project.
 

Hi,

I_peak is already explained
I_avg tells you about the motor torque
I_RMS is good if you want to calculate winding loss. (heating)

Klaus
 

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