INVERTER DEVICE

PROBLEM TO BE SOLVED: To inexpensively provide an inverter device which, when a motor for a compressor is controlled by a so-called sensorless vector control, prevents breakage of piping and contributes also to energy saving. SOLUTION: The inverter device 1 controls the motor 6 for the compressor constituting a refrigerant circuit. This device includes: an inverter main circuit 3 which applies a three-phase PWM system of a three-phase pseudo AC voltage to the motor; a shunt resistor 2 for converting a current flowing through the motor into a voltage; an OP amplifier 31 which amplifies a terminal voltage of the shunt resistor; and a control device 11 which detects the current flowing through the motor from the output of the OP amplifier, estimates a rotor position of the motor based on the detected current, and controls ON/OFF operation of the respective switching elements of the inverter main circuit. In a situation where an output voltage of the OP amplifier, into which the terminal voltage of the shunt resistor is input, is put into a saturation state, the control device changes control coefficient in a direction of decreasing change in the current flowing through the motor. COPYRIGHT: (C)2011,JPO&INPIT