Motor drive device and air conditioner

A motor drive device comprising:

• a supply power generator to convert electrical power supplied from a commercial power supply, into direct current electrical power;
• an inverter output circuit to drive a motor using electrical power supplied from the supply power generator;
• a voltage detector to detect a voltage value of a direct current voltage being applied to the inverter output circuit by the supply power generator;
• a current t detector to detect a current value of a current being supplied from the inverter output circuit to the motor;
• a current limiting resistor and a current change-over switch connected in parallel between a bus and the voltage detector, the bus connecting the supply power generator and the inverter output circuit to each other, wherein the current change-over switch switches a short circuit path between both ends of the current limiting resistor to either an ON state or an OFF state;
• and
• first processing circuitry to control the inverter output circuit based on a detection result of the voltage detector and to control turning on and off of the current change-over switch based on the current value, wherein
• the first processing circuitry
• transmits a voltage of the bus to the voltage detector through the current change-over switch by turning on the current change-over switch when the motor is to be driven, and
• transmits the voltage of the bus to the voltage detector, not through the current change-over switch, but through the current limiting resistor, by turning off the current change-over switch when the current value changes only by an amount less than a first threshold in a first time period during driving of the motor.