Question

When configuring a Variable Frequency Drive, which parameter must be specifically tuned to prevent the motor from stalling during a sudden increase in mechanical load?

Accepted Answer

The parameter that must be tuned to prevent motor stalling during a sudden increase in mechanical load is the torque boost or voltage boost. A Variable Frequency Drive controls a motor by adjusting the frequency and voltage of the electrical power supplied to it. At low speeds, the inherent resistance in the motor windings causes a significant voltage drop, which reduces the magnetic flux required to produce torque. Torque is the rotational force the motor exerts to turn a load. When a sudden mechanical load is applied, the motor requires extra torque to maintain its speed. If the torque is insufficient, the motor slows down or stalls, which means it stops rotating because it cannot overcome the resistance of the load. Torque boost compensates for the voltage drop by manually increasing the voltage applied to the motor at lower frequencies. By increasing this voltage, the drive strengthens the magnetic field inside the motor, allowing it to generate more torque to handle the sudden load increase without stalling. Tuning this parameter involves setting the boost level high enough to provide the necessary force during start-up or heavy load conditions, but low enough to avoid overheating the motor windings due to excessive current.

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When configuring a Variable Frequency Drive, which parameter must be specifically tuned to prevent the motor from stalling during a sudden increase in mechanical load?