Glossary of Motor Terms
PWM (pulse-width modulation)
PWM is a technique to vary mean voltage applied to a motor in a scheme shown in (a); the transistor is operated in a switching mode at constant frequency in this case and the period TH during which to supply voltage VS to the motor is controlled repeatedly. The average voltage can be adjusted by the time ratio (TH / To). The waveform applied across the two terminals of the motor is such as shown in (b)，where the definitions for TH and To are given.
