In our test setup we run a motor in open loop and read angle/velocity data from AD2S1210.
When the rotor is not rotating and no PWM is applied to the motor phases, the velocity read from AD2s1210 is zero and the angle is constant as expected. But when we start to apply PWM to the motor phases (the rotor is still not rotating) the velocity data is zero but angle data is incrementing slowly. When we monitor the sine/cosine inputs, the amplitudes seem to be stable. No error signal is asserted by AD2S1210. What might be the problem? Our PWM is 400VDC at 5kHz.