As compared to across-the-line starters, reduced voltage starters

As compared to across-the-line starters, reduced voltage starters

• A. Reduce starting torque required
• B. Reduce inertia loads
• C. Reduce accelerating time
• D. Reduce starting current inrush

Answer: (D)

When you start a motor with reduced voltage, the voltage applied during the startup phase is lowered. This directly lowers the current the motor draws from the power supply at the moment it starts, which is the inrush current the line experiences with across-the-line starters. That’s the main effect people use reduced voltage starters for: to limit electrical stress and voltage drop on the supply by reducing the starting current. Reducing the voltage also lowers the torque the motor can develop at start (since torque depends on applied voltage), so the motor’s ability to accelerate is reduced, and the accelerating time typically increases. The load’s inertia isn’t changed by the starter, and the torque needed to start the load isn’t made smaller—it’s the motor’s available starting torque that drops, not the load’s requirement. So the most direct, defining outcome is the reduction of starting current inrush.

When you start a motor with reduced voltage, the voltage applied during the startup phase is lowered. This directly lowers the current the motor draws from the power supply at the moment it starts, which is the inrush current the line experiences with across-the-line starters.

That’s the main effect people use reduced voltage starters for: to limit electrical stress and voltage drop on the supply by reducing the starting current. Reducing the voltage also lowers the torque the motor can develop at start (since torque depends on applied voltage), so the motor’s ability to accelerate is reduced, and the accelerating time typically increases. The load’s inertia isn’t changed by the starter, and the torque needed to start the load isn’t made smaller—it’s the motor’s available starting torque that drops, not the load’s requirement.

So the most direct, defining outcome is the reduction of starting current inrush.