| 摘要 |
A ground detection apparatus for electric automobile having a high-voltage DC power supply ( 31 ) which is electrically insulated from a body and a three-phase AC motor ( 33 ) which is driven by a DC voltage from the high-voltage DC power supply. A ground detection signal consisting of a square waveform is supplied to the DC power supply circuit through a detection resistor and a coupling capacitor, a voltage amplitude of a ground detection point serving as a connection point between the detection resistor ( 3 ) and the coupling capacitor ( 4 ) is detected, the detected voltage amplitude is converted into an insulation resistance on the basis of the relationship between a preset voltage amplitude and a preset insulation resistance, and levels of insulation resistance deterioration of the high-voltage DC power supply are detected by comparing the converted insulation resistance with a preset ground decision threshold value.
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