What type of starter is best suited when maximum starting torque and minimum starting current are necessary?

The autotransformer starter is the best suited choice for achieving maximum starting torque while keeping the starting current at a minimum. This type of starter utilizes an autotransformer to reduce the voltage supplied to the motor during startup. By reducing the voltage, the starting current is effectively limited, which helps to prevent electrical overstress on the motor and associated components.

At the same time, because it can tap into a higher voltage at various turns of the autotransformer, it allows for sufficient starting torque. This combination of reduced current and adequate torque makes it especially beneficial for applications with high inertia loads, where the motor needs to start gently without excessive inrush current, but still deliver enough power to start the load.

In contrast, other starter types, such as primary resistor starters, may limit starting torque significantly because they introduce resistance, causing both high starting current and low torque. Soft starters offer controlled ramp-up but might not provide enough initial torque when needed. Direct on-line starters can produce high inrush currents that may damage the motor or electrical system, particularly under load. Hence, the autotransformer starter balances the need for torque and current effectively.