An simple active-short-circuit (ASC) method is proposed for an air conditioning system. Inverters with a single shunt-resistor connected to DC-link are not able to measure the motor currents during ASC operation. Further, it makes a typical sensorless algorithm impossible to estimate the motor speed either. Consequently, it is challenging to use ASC safely for a low-cost inverter. In this paper, open-circuit and ASC are applied sequentially to stop the motor. The motor speed is estimated using a mechanical motor dynamics during the open-circuit operation. If the estimated speed becomes equal to the predetermined target speed, ASC operation is started. It not only reduces the magnitude of the magnitudes currents but also increases the braking torque. The effectiveness of the proposed method is validated by experimental results.
