Runaway

Motor Phase Current Runaway Debug

Symptom

8000 RPM on 4 A until 299 ms. Then the phase current passes 45 A and FAULT bit 0 latches. The motor's registers are in the Circuit figure.

Measured trace of the starter on the public case: the peak phase current sits near 4 A until 299 ms, jumps, reaches 45.5 A at 308 ms when FAULT bit 0 latches, and the drive trips at 313 ms, when FAULT reads 3, after which the current dies away as the shaft coasts

Circuit

Block diagram: U1 STM32F4 drives the motor plant at 0x50062000 through its registers, the plant's inverter feeds motor leads A, B and C with a shunt on each lead reporting IA, IB and IC, current probe TP1 on the leads records the FOC trace, PA9 carries text to the host console; below, the table of plant registers with offset, access and units, and the speed mailbox in RAM

Pass condition

FAULT bit 0 never sets. Even with the current fine, a wrong reading trips FAULT bit 1 before a phase passes 20 A, or 25 A during a speed change. A healthy run holds the command within 500 RPM.

Notes

The drive's host sets the command and may stop and restart the shaft in the 600 ms run. TP1 is the FOC Trace, one row per millisecond.

Related challenges

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