| 摘要 |
PROBLEM TO BE SOLVED: To reduce a capacity required for a smoothing capacitor, on the DC side of an inverter which is employed in electric automobile or the like. SOLUTION: Voltage variations across a smoothing capacitor 10 caused by deterioration thereof is detected, based on the voltage measurement of a voltage sensor 12. Voltage variation accompanying deterioration has a period corresponding to the PWM carrier frequency, and a voltage variation monitoring section 30 is provided with a band-pass filter 32, in order to extract a voltage variation component having that frequency. When an extracted voltage variation exceeds a specified abnormality decision reference level, a decision is made that the smoothing capacitor 10 is abnormal, and a vehicle is stopped. Deterioration can be detected before a vehicle is damaged by comparing a deterioration decision reference level which is set lower than the abnormality decision reference level with the voltage variation. |
