Daikin Industries, Ltd.

Naoya Yamashita

Toshiyuki Maeda

Yuji Nakazawa

Atsushi Sakawaki

Yusuke Irino

Kenichi Sakakibara

A first capacitor is connected between first and second power supply lines. A reactor is connected in series with the first power supply line or the second power supply line. A single-phase AC voltage is applied to a rectifying circuit. The rectifying circuit, which includes the first capacitor and the reactor, outputs a rectified voltage to the first and second power supply lines. A buffer circuit includes a second capacitor provided between the first and second power supply lines. The buffer circuit discharges the second capacitor at a controllable duty ratio. A booster circuit boosts the rectified voltage to charge the second capacitor. A DC current to be input to the booster circuit is reduced more as a voltage across the reactor is higher.

Charge and discharge circuit, control method for charge and discharge circuit, control device for charge and discharge circuit, and direct power converter

When a rectifying duty dr, a discharge duty dc, a voltage between both ends Vc of a capacitor, and a rectified voltage Vrec of an AC voltage are introduced, a virtual DC link voltage in an inverter is expressed by dc&#xb7;Vc+dr&#xb7;Vrec. The discharge duty is a time ratio at which a switch is conductive. The rectifying duty has a value obtained by subtracting the discharge duty and a zero voltage duty from 1. The zero voltage duty is a time ratio at which the inverter adopts a zero voltage vector irrespective of the magnitude of a voltage output from the inverter. In a boost chopper, the capacitor is charged during a part of a period during which the virtual DC link voltage is greater than the rectified voltage.

Direct AC power converter

A converter full-wave rectifies a single-phase voltage, and outputs the rectified voltage across DC power supply lines. An inverter receives the rectified voltage, and supplies a three-phase AC current to an inductive load. A power buffer circuit is connected between the DC power supply lines. The power buffer circuit includes a discharge circuit and a charge circuit. The discharge circuit includes a capacitor and a switch connected in series to each other. The discharge circuit is configured, for example, by a boost chopper, and includes a switch, a reactor, and a diode. The power buffer circuit provides and receives part of pulsations of a power input into the converter to and from the DC power supply lines.

Power converter with a power buffer circuit whose buffered power is smaller than an AC component of a pulsating power

A DC link has first and second power supply lines. A first rectifying circuit has a plurality of input terminals that input an AC voltage and a pair of output terminals connected to the DC link. An inverter converts a voltage applied to the DC link into another AC voltage. A boost chopper has a capacitor at an output stage. A switch switches discharge and non-discharge from the capacitor to the DC link. In the boost chopper, charge into the capacitor is performed at least at a first period. The first period is a part of a period during which a discharge duty as a time ratio of continuity of the switch is larger than 0.

Direct AC power conversion device

A magnetic bearing body supports a rotating shaft using a combined electromagnetic force of a pair of control electromagnets without contact. A controller detects a control index value based on a first coil current passed through a coil of a first control electromagnet of the pair of control electromagnets which generates an electromagnetic force in the same direction as that of a load exerted on the rotating shaft, the control index value being an index of the degree of margin for error in control depending on a value of the first coil current. And the controller controls a middle value of a pair of coil currents passed through the respective corresponding coils of the pair of control electromagnets so that the control index value approaches a predetermined target index value.

Magnetic bearing device and compressor

A stator is provided which exerts a combined electromagnetic force of a plurality of electromagnets on a drive shaft having a fluctuating load. A controller is provided which controls a current difference between a first coil current passed through a coil of the electromagnet generating an electromagnetic force in a direction opposite to that of the load and a second coil current passed through a coil of the electromagnet generating an electromagnetic force in the same direction as that of the load to perform a position control on the drive shaft. The controller adjusts the second coil current to reduce an average value of the second coil current.

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Kusatsu, Japan

Naoya Yamashita