Patent ID: 8106667

Claim:
An insulation measurement apparatus, comprising: a path comprising: a first resistor; a capacitor in a state electrically floated from a ground potential; and a second resistor, wherein the first resistor, the capacitor, and the second resistor are coupled in series sequentially from a positive electrode side of a power supply to a negative electrode side of the power supply; a first switching element provided in a path from the positive electrode side of the power supply to the capacitor; a second switching element provided in a path from the capacitor to the negative electrode side of the power supply; a detection section configured to: detect a charge voltage set to the capacitor; and determine an insulation state of the power supply; and a voltage setting section configured to execute: a power supply voltage measurement mode for charging the capacitor by a voltage of the power supply for a predetermined voltage applying time period to measure the voltage of the power supply, and an insulation voltage measurement mode for charging a terminal of a positive electrode side or a negative electrode side of the capacitor via an insulation resistor between the positive electrode or the negative electrode of the power supply and the ground potential for a predetermined voltage applying time period to measure a voltage of the insulation resistor by controlling the first and second switching elements, wherein a charge resistance value at a time of charging the capacitor by the voltage of the power supply in the power supply voltage measurement mode is set to be a sum of a value of the first resistor and a value of the second resistor, wherein a charge resistance value at a time of charging the terminal of the positive electrode side or the negative electrode side of the capacitor via the insulation resistor between the positive electrode or the negative electrode of the power supply and the ground potential in the insulation voltage measurement mode is set to be a sum of the value of the first resistor or the value of the second resistor and the insulation resistor, wherein each of the value of the first resistor and the value of the second resistor is set to be same as an insulation resistance value of a threshold value of a value representing the insulation state, and wherein a voltage applied to the capacitor and the voltage applying time period thereof when the detection section determines that the insulation state coincides with the threshold value are respectively same as a voltage applied to the capacitor and the voltage applying time period thereof at a time of charging by the voltage of the power supply.