Patent ID: 7928686
Filing Date: 2011-04-19
Classification: B60K,B60L,B60W,H02P,Y02T

Abstract:
1. An electric motor control device comprising: a direct current power source; an inverter interposed between an electric motor and the direct current power source, the inverter device controlling an exchange of electric power therebetween; an inverter control unit that generates PWM pulses having a duty ratio corresponding to voltage command signals and sends the PWM pulses to the inverter in order to switch the inverter; a frequency changing unit that changes a carrier frequency of the PWM pulses generated by the inverter control unit in a manner corresponding to a frequency control signal; and a motor control unit that provides, when a target torque and a rotational speed of the electric motor are in a predetermined region, the frequency changing unit with the frequency control signal that sets the carrier frequency to a high frequency, and during this switching, if a voltage control mode that controls three phase voltages of the electric motor is a three-phase modulation mode in which each of the three phase voltages is controlled through PWM, switches the mode to a two-phase modulation mode in which two phases are controlled through PWM while PWM switching is not applied to the other one phase, that provides, when the target torque and the rotational speed are outside of the predetermined region, the frequency changing unit with the frequency control signal for setting the carrier frequency to a low frequency that is lower than the high frequency, and that provides the inverter control unit with the voltage command signals that makes an output torque of the electric motor coincide with the target torque.