The motor that can be started manually with a rheostat is which type?

Master the Motor Controls Level 3 Test. Engage with flashcards and detailed multiple-choice questions, complete with hints and thorough explanations. Prepare effectively for your exam!

Multiple Choice

The motor that can be started manually with a rheostat is which type?

Explanation:
A DC motor is started with a rheostat because the armature current is very high at standstill, since back-EMF is zero. Placing a variable resistor in series with the armature lets you manually limit that starting current and then gradually increase it as the motor speeds up, giving a smooth, controlled start. This approach isn’t practical for typical AC motors, where starting is managed with other methods (like autotransformers or soft starters) and where a simple rheostat in the stator doesn’t provide the same controlled benefit. Synchronous motors require different starting methods to bring the rotor into step with the stator field, so a rheostat isn’t used for them in the same way. So, the motor type that can be started manually with a rheostat is a DC motor.

A DC motor is started with a rheostat because the armature current is very high at standstill, since back-EMF is zero. Placing a variable resistor in series with the armature lets you manually limit that starting current and then gradually increase it as the motor speeds up, giving a smooth, controlled start. This approach isn’t practical for typical AC motors, where starting is managed with other methods (like autotransformers or soft starters) and where a simple rheostat in the stator doesn’t provide the same controlled benefit. Synchronous motors require different starting methods to bring the rotor into step with the stator field, so a rheostat isn’t used for them in the same way. So, the motor type that can be started manually with a rheostat is a DC motor.

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