Research On The Revising Problems Of New DCM

Although brush DC motors had perfect operation performances; mechanical commutation limited their structure simplification, maintenance and application field. Brushless DC motors (BLDCMs) used electronic commutation instead and solved the preceding problems. However, as a matter of fact, BLDCMs are Permanent Magnet AC Synchronous Motors, whose congenital weaknesses were obvious:winding inductance limited the output power and the control of winding current was more complicated.Professor Wang Zong-pei, a well-known motor expert of China, proposed the thought of New DC Motors (New DCMs in short) with dc-armature winding circuit and electronic commutation. A large number of theoretical and experimental research work on New DCM’s body structure and its drive and control strategies were carried out by our team. The results showed that the New DCM had better operation performances than BLDCMs.A brush DC motor armature circuit has independent commutation circuit, thus commutation process has no effect on the main circuit. While New DCM armature circuit is related to the structure of electronic commutator, conduction logic, self and mutual inductance of commutation unit. Due to the influence of the armature reaction, the polarity of the commutation unit Back-EMF was changed before New DCM inverting, the branch current and commutation circulation current were existed in commutation unit.Aiming at the problems of the circulating current and low torque-speed characteristic of New DCM caused by armature reaction, the structure of electronic commutator, operating principle, conduction logic, armature reaction and the armature circuit of the New DCM with nine commutation units were discussed, while the cause of the circulating current in the commutation unit was analyzed. Then an advanced angle control mode was proposed on the analysis of the armature circuit. Finally an experiment was conducted on the experimental platform of New DCM. The results indicate that the torque-speed characteristic can be improved and the circulating current can be reduced in the new mode. Therefore, the feasibility of the solution is confirmed.