INVERTER

摘要

PROBLEM TO BE SOLVED: To enhance the efficiency by controlling the conduction angle variably such that a three-phase inverter sets the conduction waveform of a DC three- phase brushless motor within a specified angle per phase thereby preventing the ON loss and switching loss due to forward voltage drop. SOLUTION: Voltage of an AC power supply 1 is converted into a DC voltage and then passed through an inverter 3 to produce a pseudo AC voltage which is applied to a DC three-phase brushless motor 4. The inverter 3 controls the conduction angle variably such that the conduction waveform per phase will be within 120 deg. in a conduction phase where magnets buried in the rotor of DC three-phase brushless motor perfectly face the field winding of stator at 0 deg. when the waveform is symmetric from -600 deg. to +60 deg. around 0 deg. and from +120 deg. to +240 deg. around +180 deg.. According to the arrangement, motor efficiency can be enhanced by decreasing the number of switching times of inverter 3 without varying the voltage amplitude.