Power inverter with overload protection apparatus

摘要

A power inverter including a converter unit for rectifying AC power into DC power, an inverter for inverting the DC power into AC power for driving a load apparatus, and a protection apparatus for protecting the load apparatus from being overloaded. The load protecting apparatus comprises current detecting means for detecting a current supplied to the inverter unit from the converter unit, a memory for storing a thermally limited operation time characteristic determined in consideration of cooling effect proper to the load apparatus, and an abnormality detecting circuit for producing an abnormality signal to stop the operation of the inverter unit when an accumulated value calculated on the basis of the current value detected by the current detector at a predetermined sampling interval exceeds the characteristic value previously stored in the memory. The load apparatus can be positively protected from overload notwithstanding variations in the output voltage and the output frequency of the power inverter.