AnsweredAssumed Answered

3 shunt current measurement

Question asked by yermolayev.ivan on Nov 16, 2015
Latest reply on Jan 10, 2016 by wolff.roger
Hi everyone,

I'm using the following evaluation boards:
    - STM32303C-EVAL
    - STEVAL-IHM023V3

I'm trying to make FOC algorithm for ACIM. The whole FW is written by myself excluding the standard peripheral lib from ST. At the moment the motor is controlled with the U/f algorithm.   
PWM timer is configured to 200 us. ADC is configured for measuring the currents, when the bottom IGBTs are ON. The trigger of the ADC interrupt comes once per PWM cycle in the middle of the current pulse, when the current flows through the shunt. 

I've soldered up the 150 pF capacitors on the STM32303C-EVAL board, so that the RC time constant is 150 ns. 
The measured current is sent via UART and built in Excel. 

The result of measurement you can see in the attached picture.   

As you see the current indeed has a sine form, but it also has some low frequency noise, that I can't filter. In my opinion this kind of current signal isn't good enough for FOC. 

Can you advice me something, how can I improve it? 

Thank you in advance,