Which risk increases when variable-frequency drive (VFD)-controlled motor's braking resistor's isolating breaker fails open when regenerative braking is enabled?

💡 Explanation

A failed open braking resistor breaker prevents dissipation of regenerative energy via dynamic braking; this causes a DC bus *overvoltage* because mechanical energy converts to electrical energy faster than the inverter’s capacitors can handle it. Therefore, overvoltage tripping increases, rather than frequency instability under normal operation.

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