Power losses in outside-spin brushless d.C. motors

Abstract

Outside-spin brushless D.C. motors are an alternative to conventional D.C. brush permanent magnet motors, especially in applications that require low power and costs and in which high inertia effects are advantageous. This paper presents a procedure for computing power losses in these kinds of machines. Expressions are derived for predicting copper losses, power interrupter losses, stator iron losses in the tooth and in the yoke, mechanical losses, friction and windage. Stray load losses are also considered and evaluated from previous measurements in outside-spin brushless D.C. motors. The results obtained from the approach proposed are compared to those measured on existing motors, showing a good agreement.