Which characteristic of a PWM waveform allows for fine control over motor performance?

The duty cycle of a PWM (Pulse Width Modulation) waveform is the key characteristic that enables fine control over motor performance. The duty cycle refers to the percentage of one period in which the signal is active or 'high' relative to the total period of the waveform. By adjusting the duty cycle, the average power delivered to the motor can be finely tuned.

For instance, a higher duty cycle means the PWM signal is 'on' for a larger portion of the time, effectively increasing the average voltage and current supplied to the motor. This leads to increased speed or torque. Conversely, a lower duty cycle reduces the average power, which can slow the motor down or reduce torque.

This precise control is crucial in applications such as variable speed drives where fine adjustments are needed to achieve the desired operational efficiency. The other characteristics—frequency, amplitude, and phase shift—while relevant to PWM signals, do not provide the same level of granularity in controlling motor performance as the duty cycle does. Frequency affects how quickly the PWM signal switches on and off, amplitude is related to the maximum voltage level of the signal, and phase shift pertains to time alignment between signals, all of which play supporting roles but do not directly influence the effective power control as the duty cycle