Short circuits

Argon has pretty sophisticated circuit protection functionality. The device has sub-microsecond response short circuit sensing circuit that can detect phase-to-phase and phase-to-ground shorts. To counter harsh environment EMI and prevent false fault triggering, there is variable length digital delay filter for short circuit protection┬á – and this parameter is also user adjustable.

SC scoping

Short circuit scoping. Yellow trace is IGBT phase current 67 A/div and blue is power stage shutdown signal from DSP.

The oscillograph above displays a phase-to-ground short circuit when shorted by a piece of wire right at output terminals. Drive was driving an AC motor at supply voltage of > 200 VDC while wire is shorted to ground. The yellow output current graph shows current of 170 Amperes and pulse length of about 2 ┬Ás before shutdown was issued. I believe the blue digital trace is fluctuating because board’s ground plane is struggling to carry the enormous current.

The test has been repeated dozens of times with varying protection delay times and supply voltages, and no harm to hardware was ever induced. I’m satisfied.

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