Disconnecting external DC power with the spike suppression switch in the START PROTECTION position will result in which event?

• A. DC Bus Short
• B. Generator Failure
• C. Battery Drain
• D. Inverter Trip

Answer: (A)

When the spike suppression function is set to START PROTECTION, the spike suppression path is engaged in a way that ties into the DC bus to handle transient voltages during starting. If you disconnect the external DC power while that setting is active, you effectively leave the spike suppression network across the DC bus without the external source feeding it. The result is a direct, low-impedance connection between the positive and negative rails of the DC bus—a DC bus short. That sudden short draws a large current, which will trigger protective devices and create a fault condition on the bus itself.

The other options describe secondary consequences rather than the immediate fault. A generator failure would imply the generator itself has failed, which isn’t what happens when you remove external power in this configuration. Battery drain could occur if a load remained, but the decisive event is the abrupt short on the DC bus, which is why a DC bus short is the best answer. An inverter might trip as a consequence of the bus fault, but the primary event is the short circuit on the DC bus.