Motor-driven compressor

Abstract

A motor-driven compressor includes a compression portion, an electric motor, a motor drive circuit having switching element, a temperature detector, and a switcher, which switches the drive mode of the motor drive circuit. When acquiring information indicating that the temperature detected by the temperature detector has increased and reached a first preset temperature, the switcher switches the drive mode of the motor drive circuit from a first drive mode to a second drive mode. Also, when acquiring information indicating that the temperature detected by the temperature detector has increased and reached a second preset temperature, which is higher than the first preset temperature, the switcher switches the drive mode of the motor drive circuit from the first drive mode or the second drive mode to a third drive mode.

1 . A motor-driven compressor comprising:
 a compression portion;   an electric motor, which drives the compression portion;   a motor drive circuit, which drives the electric motor, wherein the motor drive circuit has a switching element for converting a DC voltage into an AC voltage;   a temperature detector, which detects a temperature of the switching element; and   a switcher, which switches a drive mode of the motor drive circuit to one of a first drive mode, a second drive mode, and a third drive mode, which are determined by a carrier frequency and modulation control, wherein   when acquiring information indicating that the temperature detected by the temperature detector has increased and reached a first preset temperature, the switcher switches the drive mode of the motor drive circuit from the first drive mode to the second drive mode, and   when acquiring information indicating that the temperature detected by the temperature detector has increased and reached a second preset temperature, which is higher than the first preset temperature, the switcher switches the drive mode of the motor drive circuit from the first drive mode or the second drive mode to the third drive mode.   
     
     
         2 . The motor-driven compressor according to  claim 1 , wherein
 in the first drive mode, two-phase modulation control is executed by using a predetermined first carrier frequency,   in the second drive mode, three-phase modulation control is executed by using a second carrier frequency, which is lower than the first carrier frequency, and   in the third drive mode, two-phase modulation control is executed by using a third carrier frequency, which is lower than the first carrier frequency.   
     
     
         3 . The motor-driven compressor according to  claim 2 , wherein
 the first carrier frequency is outside the audible range,   the second carrier frequency is within the audible range, and   the third carrier frequency is within the audible range.   
     
     
         4 . The motor-driven compressor according to  claim 2 , wherein
 when acquiring information indicating that the temperature detected by the temperature detector has dropped to a third preset temperature, which is lower than the second preset temperature, the switcher switches the drive mode of the motor drive circuit from the third drive mode to the second drive mode, and   when acquiring information indicating that the temperature detected by the temperature detector has dropped to a fourth preset temperature, which is lower than the first preset temperature, the switcher switches the drive mode of the motor drive circuit from the second drive mode or the third drive mode to the first drive mode.   
     
     
         5 . The motor-driven compressor according to  claim 4 , wherein the first preset temperature, the second preset temperature, the third preset temperature, and the fourth preset temperature are set to not exceed a heat resistance temperature of the switching element such that a temperature range in which the motor drive circuit is driven in the first drive mode is wider than a temperature range in which the motor drive circuit is driven in the second drive mode and a temperature range in which the motor drive circuit is driven in the third drive mode. 
     
     
         6 . The motor-driven compressor according to  claim 5 , wherein the first preset temperature, the second preset temperature, the third preset temperature, and the fourth preset temperature are set to not exceed the heat resistance temperature of the switching element such that a temperature range in which the motor drive circuit is driven in the third drive mode is narrower than the temperature range in which the motor drive circuit is driven in the second drive mode. 
     
     
         7 . The motor-driven compressor according to  claim 1 , wherein
 the first preset temperature is set in a range between 60° C. and 80° C., inclusive, and   the second preset temperature is set in a range between 80° C. and 100° C., inclusive.