Estimation of Magnet Temperature Using Disturbance Observers of Permanent Magnet Synchronous Motor for Driving Single Rotary Compressor Without Lookup Table

The growing global demand for household air conditioners necessitates reliable and efficient motor operation under high-temperature conditions. Single rotary compressors, widely used in air-conditioning systems, suffered from excessive speed ripples, noise, and vibration caused by significant load torque pulsations. This paper developed an innovative method for estimating magnet temperature for air-conditioning motors without lookup tables in conjunction with reducing the speed ripple through precise load torque estimation. A dual observer system is adopted, enabling independent gain settings for both the load torque observer and speed observer, thereby enhancing estimation accuracy and dynamic response. By estimating the load torque pattern, the proposed method reduces speed ripple and estimates magnet temperature without relying on lookup tables. In this study, magnet temperature can be determined from the voltage equation, with a permissible torque reference modification. By applying the proposed method, speed ripple was reduced by 74.3% compared with pre-compensation levels, and the magnet temperature estimation error was within 5 °C for a temperature increase from 26 °C to 76 °C. These results confirm the robustness, computational efficiency and feasibility of the proposed method, making it suitable for low-cost embedded systems in household appliances.