Part Number: TIDA-010265
I am running a 2-pole induction motor using TI’s IM Field-Oriented Control (FOC). I am commanding a speed corresponding to 50 Hz, and the feedback shown by the FOC algorithm is also around 50 Hz.
However, when I observe the phase-to-phase voltage waveform on an oscilloscope, the fundamental frequency appears to be around 40-42 Hz, not 50 Hz. The measured motor speed using a tachometer is about 2450–2460 RPM, which corresponds to approximately 40-42 Hz electrical frequency.
From classical induction motor theory and V/f (scalar) control, my understanding is that when 50 Hz is applied, the stator phase to phase voltage frequency observed on the scope should also be 50 Hz, and slip should primarily appear in the rotor speed.
To cross-check this, I ran the same motor using V/f control (DMC Level-2) with a 50 Hz command. In this case, the phase-to-phase voltage frequency observed on the oscilloscope was 50 Hz, the estimator feedback was around 45–46 Hz, and the measured motor speed was approximately 2970 RPM, which aligns with expected slip behavior.
Could you please clarify whether this behavior is expected in IM FOC operation, or if it indicates an issue in configuration or control?
Specifically, in IM FOC, should the phase-to-phase stator voltage frequency observed on the oscilloscope match the commanded frequency (50 Hz), or is it normal for the observed voltage frequency to differ from the commanded value and instead track the measured rotor speed?
