Torque Expressions and Equivalent Circuits for Salient Pole Synchronous Machines

Abstract

Two different torque expressions are proposed for salient pole synchronous machines. One is the traditional torque-voltage equation. The other is a torque-current equation and has been recently used for permanent magnet synchronous motors. Both these expressions have two terms. According to a general interpretation, one of the terms represents the magnet torque and the second term represents the reluctance torque. However, the corresponding terms in these two expressions do not give the same value when the expressions are used for an interior permanent-magnet synchronous motor. The aim of this study is to demonstrate this disagreement and identify the reason for the same by using two different equivalent circuits for salient pole synchronous machines.