Simple explanation how a controller works.
Controllers are sometimes refered to as being “pulse width modulated”. (PWM) The controller is completely electronic in nature. Transistors (mosfets, IGBTs) are relied on to control speed in conjunction with the standard transmission. Such an arrangement provides a smooth acceleration and an infinitely variable speed range. As the driver steps on the accelerator, the control circuit causes the transistors to allow a pulsating current to flow from the battery pack to the motor. When the accelerator is depressed only a small amount, the percentage of time current is allowed to flow is very small (small pulse width) and the percent of time no current is flowing is very large. The motor will turn slowly.
As the driver depresses the accelerator further, the transistors allow the current to flow a greater percentage of time, (wider pulse width) thus causing the motor to speed up.
As the accelerator is depressed yet further, the current will be flowing more often than it is not, (very wide pulse width) and the motor will run faster. The pulses of current are very fast, (~ 16000 hertz) and they become for all practical purposes, a smooth controlled current to the motor.
John Emde
Pioneer Conversions
