| 摘要 |
In a method and apparatus for protecting a plurality of same semiconductor switching elements used in a PWM inverter from being overheated, a junction temperature rise Tn of one of the switching elements is derived on the basis of an output frequency of the inverter ( omega c), an output current (I) of the inverter, and a control factor (a) and when Tn>Tnref, the overheat in the corresponding switching element occurs so that a gate signal for each switching element is not inputted or an PWM off duty ratio on a pulse duty ratio of the gate signal is increased to limit the output current of the inverter.
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