On the Application of the IEC 60034-2-1 Standard to Line-Start Synchronous Reluctance Motors

The IEC 60034-2-1 standard does not specify a method for three-phase line-start synchronous motors (LS-SynRMs). Although the direct input-output method can be easily applied, it does not specify how to correct the losses to a reference ambient temperature. This paper analyzes the applicability of the methods specified in the IEC 60034-2-1 standard to LS-SynRMs. The impact of ambient temperature on the full-load efficiency of LS-SynRMs is assessed. A method for segregating motor losses and correcting the average temperature and losses of the stator windings to a reference ambient temperature is proposed, ensuring that the stated full-load efficiency of the motor is determined accurately regardless of the ambient temperature in the laboratory where the tests are performed. Results from experiments conducted on two commercial LS-SynRMs are provided. It was observed that reducing the ambient temperature from 45 °C to 5 °C may increase the full-load efficiency of the tested LS-SynRMs by more than 1 percentage point, mainly due to the reduction of stator winding losses. Consequently, a motor manufacturer may consider testing this type of motor at lower ambient temperatures to achieve a higher efficiency class. Therefore, it is necessary to define a method for determining the efficiency of LS SynRMs that accounts for the correction of stator winding conduction losses to the standard reference ambient temperature of 25 °C. This paper intends to offer information that may contribute to overcoming the shortcomings and omissions of the IEC 60034-2-1 standard concerning the efficiency determination of LS-SynRMs, which is a relatively new technology on the market that is believed to be able to compete with line-operated induction motors in the low-power range, offering higher efficiency and constant operating speed.