The Interior Permanent-Magnet Brushless DC Motor (IPMBLDCM) without exciting winding and exciting source is widely used to replace traditional DC motors for subway locomotives. IPMBLDCM is gaining a great deal of interest for subway locomotive applications due to its high efficiency, simple control mode and small size.
PMBLDCM has a wide speed regulation range and its start current, start torque and starting time are small. Also, PMBLDCM generates enough torque and speed by the combination mode of motor/generator. From zero to base speed, it is dependent on applied voltage, and above the base speed, it is dependent on flux weakening by torque angle.
Cha Myong Song, a section head at the Faculty of Electrical Engineering, has proposed a winding design and lead angle control method for the maximum speed of an IPMBLDCM for subway locomotives.
The maximum speed of the IPMBLDCM is regulated by the linkage flux and armature reaction by lead angle control because permanent magnet magnetomotive force (mmf) cannot be regulated directly. The maximum speed of IPMBLDCM for the subway locomotive is 2.34 times the rated speed. As the speed regulation ratio is larger than 2, the maximum speed of motor must be ensured by lead angle and conductors per slot. If the lead angle is regulated, no-load speed is increased by changing linkage flux at no-load state and the rated speed is increased by armature reaction.
He simulated the relation between the speed, torque, output power and efficiency for the lead-angle and conductors per slot by means of Ansoft Maxwell/RMxprt. The simulation results verified that the speed, torque, output power and efficiency are constant in the range of 47°-68° and the maximum speed is 1948r/min. The experimental results indicated that the operation of the IPMBLDCM is stable at the maximum speed.
For more information, please refer to his paper “Winding Design and Lead-Angle Control for the Maximum Speed of an Interior Permanent-Magnet Brushless DC Motor” in “Journal of Electrical Power & Energy Systems” (SCI).
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