3 Comparison of different inverters
The inverter mentioned here is an electronic commutation (phase) circuit composed of power switching devices. In general, there are basically two types of inverters used in brushless DC permanent magnet motors and self-controlled permanent magnet synchronous motors: unipolar inverters and bipolar inverters.
A unipolar inverter is an unbridged electronic commutation (phase) circuit consisting of three power switching devices. When the motor uses a unipolar inverter, the current in the armature winding can only circulate in one direction and cannot flow in reverse. This way the winding utilization is not high: but in operation, the supply voltage is only consumed on one power switching device. Therefore, it is suitable for low-power and low-voltage brushless DC permanent magnet motors (BLDCM), of course, the price is also lower, and can only be used as a controller for two-quadrant operation.
A bipolar inverter is a bridge electronic commutation (phase) circuit consisting of six power switching devices. Bipolar inverters are classified into 120° continuity and 180° continuity. The arrangement of the Hall sensors in both cases differs by an electrical angle of 30°. The 120° turn-on inverter is suitable for brushless DC permanent magnet motors (BLDCM); the 180° turn-on inverter is the basis for sinusoidal pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM). Suitable for self-controlled permanent magnet synchronous motors (PMSM).
When the motor adopts a bipolar inverter, the current in the armature winding can flow in both forward and reverse directions, the winding utilization is high, the output power or output torque of the motor is also large, and it can be operated in four quadrants. The controller, of course, is also relatively expensive.
As for the use of bipolar inverters, the supply voltages consumed on the two power switching devices will become smaller and even negligible as semiconductor technology evolves.
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