[Ether]

Originally Posted by zbrozek

I've spent the evening fussing with a CIM and a black Jaguar (firmware version 107) on my bench.

Would you please confirm that I am interpreting your test conditions and scope traces correctly? Thank you:

It's not actually very well balanced (magnetically or mechanically). This manifests as significant torque ripple even with constant terminal voltage. Trace - yellow is terminal voltage, red is current.

The above is with power supply connected directly to CIM (no Jag in circuit), supplying approx 2.7 volts (yellow trace) directly to the CIM leads, resulting in approx 2.4 +/- 0.6 amps at 150Hz (red). No load on the motor shaft (nothing connected, not even a dyno set to zero).

Check out the trace. Red is actual motor current (as measured with a Tektronix A622). Blue is motor-applied voltage. Yellow is INA193 output.

The above is with power supply approx 13.7 volts to Jag. Jag is connected to CIM. Jag is set for approx 17.5% output duty cycle (blue trace) at approx 15KHz.

Red trace is actual motor current measured in the motor lead (not in the power supply line). Approx 5.4 +/- 1.1 amps.

What is the load on the CIM output shaft?

At no-load it looks like this.

No load on the motor shaft (nothing connected, not even a dyno set to zero).

I'm not an expert on brushed motors, maybe someone else can explain how the near-square bus current waveform results in a triangular motor current waveform.

During the "off" portion of the duty cycle, the motor leads are shorted, and the current continues to flow through the motor due to the motor inductance.