Daikin Industries, Ltd.

Yasutaka Taguchi

Morimitsu Sekimoto

Tomoisa Taniguchi

Junya Mitsui

Akira Moriguchi

An electric power conversion device includes: a converter circuit which includes a boost chopper; a capacitor which is connected between output terminals of the converter circuit; a boost chopper which boosts a terminal voltage of the capacitor; a multiphase inverter circuit; and a boost chopper controller. In a case where the operation of the boost chopper is continuously stopped, the capacitor has a capacitance allowing the terminal voltage of the capacitor to have a pulse frequency twice as high as that of the AC power source. The multiphase inverter circuit has an output power which is allowed to fluctuate in synchronization with a power source.

Electric power conversion device

A power converter including a compressor as a load includes a compensation current output () allowing compensation current (Ic), which compensates for leakage current (Ia), to flow. A controller () receives a detection signal from a rotational speed sensor () which senses the rotational speed of the compressor (CM). When the rotational speed has increased to a set rotational speed at which the leakage current (Ia) is lower than or equal to its limiting value (Lmax) (e.g., the limiting value specified under the Electrical Appliances and Materials Safety Act or by the IEC) in a state where the compensation current output () is off, the compensation current output () is switched from an on state to an off state. This may reduce the leakage current from the compressor with low power loss.

Power conversion device

A converter to which an alternating current is inputted from an AC power supply rectifies the alternating current to output it to a DC link. An inverter is connected through the DC link to the converter and converts a direct current into an alternating current to output it to a load. A leakage current detector outputs a detection current corresponding to a leakage current leaking from the load. A compensating current output end is connected to a location where the leakage current leaks, and outputs a compensating current compensating for the leakage current in response to the detection current. A switch sets whether to input the detection current to the compensating current output section or not.

Leakage current detection and switched on/off compensating current

A diode bridge has a pair of input ends to which an alternating current is inputted from an AC power supply, and a pair of output ends which output a direct current. A boost chopper circuit is connected to the pair of output ends, and sets up a DC voltage inputted thereto. The boost chopper circuit functions as a power factor correction circuit. A smoothing capacitor is connected to an output side of the boost chopper circuit, and smoothes the voltage across the smoothing capacitor. An inverter receives the voltage across the smoothing capacitor to apply AC power to a load. A leakage current reduction device outputs a compensating current which compensates for a leakage current leaking from the load. The leakage current reduction device outputs the compensating current, except near the zero crossing of an AC voltage inputted from the AC power supply.

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Osaka, Japan

Yasutaka Taguchi