Constant Margin-Angle Control of Commutatorless Motor Using Microcomputer

Constant margin-angle control is a triggering scheme that can eliminate the commutation failure and increase the power factor and efficiency of commutatorless motors. The described scheme does not need to detect the margin angle, but the dc current and overlap angle are detected instead. The margin angle is controlled by using a correction table of the lead angle in terms of the dc current, which provides a practical solution to implement the constant margin-angle control. The problems introduced by the scheme, the occurrence of instability and commutation failure, are discussed, and methods to eliminate them are presented. Experimental results confirm the validity of this scheme.