Patent ID: 8159230

Claim:
An insulation measurement method in an insulation measurement apparatus of a flying capacitor type, the insulation measurement method comprising: a first power supply charge voltage measurement step of applying a voltage of a power supply to a flying capacitor for a first charge time period; a first grounding resistor measuring voltage measurement step of applying the voltage of the power supply to the flying capacitor via an insulation resistor on one electrode side of the power supply; a second power supply charge voltage measurement step of applying the voltage of the power supply to the flying capacitor for a second charge time period; a second grounding resistor measuring voltage measurement step of applying the voltage of the power supply to the flying capacitor via an insulation resistor on the other electrode side of the power supply; and an insulation resistor conversion step of obtaining a value of the insulation resistor based on measurement results of the first and second charge voltage measurement steps and the first and second grounding resistor measuring voltage measurement steps and an insulation resistor conversion expression, wherein in a first measuring process conducted in a state that a voltage measurement device for measuring the voltage of the power supply is normal, the charge time period of each of the first and second power supply charge voltage measurement steps and the first and second grounding resistor measuring voltage measurement steps is set to be a time period insufficient for fully charging the flying capacitor, and wherein in a second measuring process conducted in a state that the voltage measurement device for measuring the voltage of the power supply is not normal, the charge time period of each of the first and second grounding resistor measuring voltage measurement steps is set to be a time period insufficient for fully charging the flying capacitor and each of the first charge time period and the second charge time period is set to be a time period for fully charging the flying capacitor, and a measurement result of the voltage of the power supply measured in the first power supply charge voltage measurement step or the second power supply charge voltage measurement step is notified to a predetermined device to be originally notified from the voltage measurement device, instead of the voltage measurement device.