Encoderless motor design for servo drive applications

Improvement of output power of encoderless motor is desired in servo drive applications. However, as load on the encoderless motor increases, high frequency inductance distribution distorts so heavily that rotor position estimation becomes very difficult, which is a major technical problem hindering the improvement. This paper deals with a motor design aiming for high output power encoderless motor with concentrated winding and IPM configuration. First, reduction of armature reaction is referred to as the fundamental design concept. Next, a motor configuration realizing the concept is proposed. Then, motor design is conducted, and characteristics of a prototype motor is measured and evaluated. As a result, the prototype motor is verified to achieve basic servo motor performances and to have an almost sinusoidal high frequency inductance distribution feature without crucial distortion even when load increases. Output power of encoderless motor is enhanced by the design method presented in this paper.