Patent ID: 7898264

Claim:
A motor insulation deterioration detection device for detecting insulation deterioration in a plurality of motors connected to a motor driving apparatus comprising a converter unit having a rectifying circuit for rectifying AC power, a smoothing capacitor for smoothing an output of said rectifying circuit, and a plurality of inverters for inverting DC power output from said converter unit into AC power and for driving said plurality of motors, respectively, said detection device comprising: a single first switch which is turned on to connect one end of said smoothing capacitor to ground when detecting insulation deterioration; a single voltage detector which detects a voltage across said smoothing capacitor; a plurality of second switches which are turned on to connect the other end of said smoothing capacitor to windings of said plurality of motors, respectively, when detecting insulation deterioration; a plurality of current detectors which detect a discharge current of said smoothing capacitor that flows via insulation resistances of said plurality of motors, respectively, when said first switch and said plurality of second switches are turned on; and a plurality of insulation resistance calculators which calculate the insulation resistances of said plurality of motors, respectively, from the voltage detected by said voltage detector and the currents detected by said plurality of current detectors, wherein said single first switch and said single voltage detector are provided in said converter unit, and said plurality of second switches, said plurality of current detectors, and said plurality of insulation resistance calculators are respectively provided in said plurality of inverter units, wherein said detection device further comprises communication means for transmitting the voltage value detected by said single voltage detector and a signal notifying the timing when said single first switch is switched ON from said converter unit to said plurality of inverter units, wherein connection by said second switches, current detection by the current detectors, and calculation of the insulation resistances by the insulation resistance calculators are performed in the respective inverter units simultaneously with the same timing.