Control apparatus for electric railcar

Abstract

An object of the present invention is to minimize the switching elements' heat loss occurring when the operating frequency for PWM inverter control (that is to say, the inverter frequency) passes through a zero point, and thereby maintain sufficient braking force until the electric railcar has stopped. In such a control apparatus for an electric railcar that provides control so that when the rotational speed of the motor 12 decreases below the required value, the torque of the motor will decrease at the required rate of change, a current limiter 4 for limiting the torque current command “(A)Iqp” output from the current command arithmetic unit 2 is provided to ensure that when the rotational speed of the motor decreases below the required value, the torque current command will be limited to a command value “(B)Iqp” smaller than that command value, and to ensure that the carrier frequency at which PWM signals are created when the switching elements of the electric power converter 9 are controlled by the carrier generator 7 is controlled to become lower than the carrier frequency existing when the rotational speed of the motor decreases below the required value.

What is claimed is:  
     
         1 . A control apparatus for an electric railcar, comprising: 
 an electric power converter for driving a motor;    a means for detecting the rotational speed of said motor; and    such a control means for said electric power converter that provides control so that when the rotational speed of said motor decreases below the required value, the torque of said motor will decrease at the required rate of change, wherein said control apparatus is characterized in that it further has    a means for providing control so that when the rotational speed of said motor reaches the speed region of the required speed or less during retardation, the torque of said motor will be smaller than the specified torque value existing when the rotational speed of said motor decreases below the required value; and    a means for providing control so that the carrier frequency at which PWM signals are created during the control of the switching elements constituting said electric power converter will be lower than the carrier frequency existing when the rotational speed of said motor decreases below the required value.    
     
     
         2 . A control apparatus for an electric railcar, comprising: 
 an electric power converter for driving a motor;    a means for detecting the rotational speed of said motor; and    such a control means for said electric power converter that provides control so that when the rotational speed of said motor decreases below the required value, the torque of said motor will decrease at the required rate of change, wherein said control apparatus is characterized in that it further has a means for providing control so that when the rotational speed of said motor reaches the speed region of the required speed or less during retardation, the torque of said motor will be smaller than the specified torque value existing when the rotational speed of said motor decreases below the required value.    
     
     
         3 . A control apparatus for an electric railcar, comprising: 
 an electric power converter for driving a motor;    a means for detecting the rotational speed of said motor; and    such a control means for said electric power converter that provides control so that when the rotational speed of said motor decreases below the required value, the torque of said motor will decrease at the required rate of change,    wherein said control apparatus is characterized in that it further has a means for providing control so that when the rotational speed of said motor decreases below the required value, the carrier frequency at which PWM signals are created during the control of the switching elements constituting said electric power converter will be lower than the carrier frequency existing when the rotational speed of said motor decreases below the required value.