A circuit model for the analysis of single phase universal motors using constant arc voltage drop

In this paper equivalent circuits for universal motor analysis including brush commutation are presented. The analysis is carried out for the cases of two commutator bars in contact with the brush, three commutator bars in contact with the brush and an arcing phase. A motor terminal AC voltage is imposed and the motor current as well as the currents in the commutating coils are calculated by numerical integration of the circuit differential equations. Results are shown and compared to test data.