Patent ID: 9479108
Filing Date: 2016-10-25
CPC Classification: F04B,F04C,G06F,H02H,H02M,H02P

Claim Text:
1. An electric compressor comprising: a compression mechanism that takes in and compresses a refrigerant; an electric motor that includes motor coils of a plurality of phases and drives the compression mechanism; a housing in which the compression mechanism and the motor are accommodated and an intake refrigerant that is taken in by the compression mechanism flows; an inverter circuit attached to the housing and located to be cooled by the intake refrigerant, the inverter circuit including switching elements which are provided to correspond to the plurality of phases; a physical quantity detector that detects a temperature of the switching elements or a physical quantity associated with the temperature of the switching elements; and a controller that controls the inverter circuit to convert DC voltage into AC voltage by switching the switching elements using a PWM wave that is generated through PWM modulation based on a result of comparison between a modulation wave, which is an application voltage command to each of the plurality of phases, and a reference carrier, the controller controlling the inverter circuit to output the AC voltage to the motor coils of the plurality of phases, wherein the switching elements rise in temperature when the controller initiates the output of the AC voltage and starts up the motor, and the temperature rise of the switching elements stops due to cooling of the switching elements by the intake refrigerant, the controller changes the carrier frequency according to a value detected by the physical quantity detector in a temperature rise period until the stop of the temperature rise, so that the carrier frequency of the reference carrier decreases with the rise in the temperature of the switching elements at the startup of the motor, the controller changes the carrier frequency according to a number of revolutions of the compression mechanism or a physical quantity associated with the number of revolutions of the compression mechanism in a post-temperature rise stop period from the stop of the temperature rise, so that the carrier frequency decreases with increase of the number of revolutions of the compression mechanism, regardless of the value detected by the physical quantity detector; and the post-temperature rise stop period is divided into a temperature drop period, during which the temperature of the switching elements drops, and a steady period, during which the temperature of the switching elements is maintained substantially constant after the temperature drop of the switching elements stops.