Why your VSD trips on a hot afternoon — four things to check
Ambient temperature, blocked filters, DC bus ripple and cable length. A field checklist before you condemn the drive.
Most “faulty drive” call-outs we attend in the afternoon are thermal, not electronic. A cabinet that sits at 38 °C at 3 p.m. is running the drive above its derating curve, and the trip is the drive protecting itself.
Work through it in order: cabinet ambient and fan filters, then the motor cable length against the drive rating, then supply imbalance across the three phases, then the DC bus capacitor age if the unit is past eight years.
If the trip only ever happens under load and only late in the shift, it is almost never the control card.
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