| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a control method wherein a arm current of a power conversion circuit constituting a PWM inverter is detected, and semiconductor elements forming the power conversion circuit are protected against an overcurrent with higher reliability based on the detected value. <P>SOLUTION: The PWM inverter 2 comprises a direct-current power supply 11, the power conversion circuit 12, shunt resistors r<SB>U</SB>, r<SB>V</SB>, and r<SB>W</SB>, an arm current detecting portion 13, a PWM signal generator 14, a first carrier oscillator 15a, a protecting means 16, a level setter 21, a level detecting portion 22, a selector switch 23, a second carrier oscillator 24, and the like. If an arm current exceeds a predetermined level, a carrier frequency is increased for a predetermine period, and thereby a section wherein the arm current is detectable is increased. <P>COPYRIGHT: (C)2004,JPO |
