| 摘要 |
PURPOSE: To enhance the power efficiency by setting the conduction angle of inverter within a predetermined range. CONSTITUTION: The inventive inverter is different from a conventional system in the point that a conduction angle control means 13 is provided. The conduction angle control means 13 determines a conduction angle corresponding to the r.p.m. of motor (operating frequency detection means 12) determined based on the information from a motor voltage detection means 11. When a conduction angle is determined, a prestored value is read out from a memory and conduction angle information is delivered to a PWM duty ratio control means 14. A phase timing is then determined based on the information of pole position (phase angle detection means 16) and subjected to PWM superposition before being delivered to a transistor drive means 15. In other words, the conduction angle of inverter is set between 120 deg. and 180 deg. for one period and the waveform of motor current is approximated to a sine wave. |
