In a solid-state DC drive, the section capable of varying speed above and below the base speed is the

• A. Control section
• B. Power section
• C. Feedback section
• D. Input section

Answer: (A)

Varying motor speed in a solid-state DC drive is done by the control section. This part contains the regulation loop that generates the command signal based on a speed reference and the actual speed measured by feedback. By adjusting that command—such as changing a PWM duty cycle or firing angle—the control section tells the power section how much voltage or current to deliver, which changes the motor speed up or down from the base speed.

The power section is where the actual high-current power is switched to the motor, but it doesn’t decide the speed by itself; it follows whatever the control signal asks it to do. The feedback section provides real-time speed (and other measurements) to the control section so the loop can correct the output for accurate speed regulation. The input section is simply the user interface for setting references and commands.