Speed and ? are two physical quantities that must be controlled in a motor drive.

• A. Torque
• B. Current
• C. Voltage
• D. Frequency

Answer: (A)

Two mechanical quantities you regulate in a motor drive are speed and torque. Speed is how fast the shaft turns, and torque is the twisting force the motor provides to move the load. Controlling speed keeps the motor following the commanded motion profile, while controlling torque ensures the motor can meet load demands, accelerate properly, and avoid stalling or overload. Because the mechanical output power is the product of torque and speed, managing both lets the drive deliver the required motion and handle changes in load reliably. Electrical signals like current, voltage, and frequency are the control actions the drive uses internally to achieve the desired speed and torque, but the practical targets are the speed and the torque themselves. If the load rises suddenly, torque control allows the drive to increase current (and thus torque) to keep speed from dropping, protecting the system and meeting the performance needs.