Dual SCR chopper as a motor controller for an electric car

Despite recent advances in solid-state controls for electric cars, chopper-induced problems still exist: commutation and ac losses are significantly high, the chopping action induces losses within the power source, and large ripple components in the chopper output cause increased rms losses at the motor. The author´s dual chopper, two conventional choppers in parallel, reduces these problems. The duty cycle generated by the firing circuit is feedback controlled so that the load current remains proportional to control output. The dual chopper operates in a three-in-one system: in the first mode, the batteries charge at high rates; the second mode controls the amount of power flowing from battery to motor; and in the third or regenerative braking mode, the chopper transfers energy from the motor to the battery.