INVERTER DEVICE

An inverter apparatus 2 includes a direct-current power supply 4, switching elements S and freewheel diodes D which are connected to the direct-current power supple 4, a means which converts a direct current voltage into a predetermined alternating current voltage, a predetermined current, and a predetermined frequency, depending on switching on/off of the switching elements S, a temperature detector C provided near at least one of the switching elements S, and a temperature estimation means 17. The Temperature estimation means 17 estimates temperature of switching elements not provided with the temperature detector, based on a loss model (Expression 1-6) of the switching elements S and freewheel diodes D, a thermal resistance model (Expression 7-9) of a module which fixes the switching elements S and freewheel diodes D, an estimated-temperature increase value calculated by the loss model and thermal resistance model, and a temperature of the switching element detected by the temperature detector C. Based on a temperature detected from one switching element, temperatures of other switching elements are estimated, regardless of operation of the inverter.