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Slip ring induction motor can be used for
Elevator
Compressor
Printing press
All of above
All of above
A slip ring induction motor (wound rotor induction motor) allows external resistance to be inserted into the rotor circuit via slip rings and brushes. This feature provides high starting torque with low starting current and enables smooth speed control under heavy loads. Because of these versatile features, it is suitable for heavy-duty applications like elevators, compressors, and printing presses.
A slip ring induction motor (wound rotor induction motor) allows external resistance to be inserted into the rotor circuit via slip rings and brushes. This feature provides high starting torque with low starting current and enables smooth speed control under heavy loads. Because of these versatile features, it is suitable for heavy-duty applications like elevators, compressors, and printing presses.
TstтАЛтИЭR2тАЛ┬░2+X2тАЛ┬░2тАЛR2тАЛтАЛ тАФ Starting torque dependence on rotor resistance
smтАЛ=X2тАЛR2тАЛтАЛ тАФ Slip at maximum torque (TmaxтАЛ)
Inserting external resistance (RextтАЛ) into the rotor circuit during startup increases the rotor power factor and shifts the point of maximum torque (TmaxтАЛ) to zero speed (standstill), achieving high starting torque (TstтАЛтИЭRrтАЛ). Once the motor accelerates to normal operating speed, the external resistance is gradually cut out, and the slip rings are short-circuited.
External resistance inserted into the rotor winding increases starting torque while keeping starting current low.
Elevators requires high starting torque under full load conditions.
Compressors require high initial torque to overcome standstill mechanical resistance.
Printing presses require smooth speed control and high starting torque to handle heavy inertia loads.
High starting torque with low starting current.
Speed control is possible by adding external rotor resistance.
Capable of starting under heavy load conditions.
Higher initial cost and complex maintenance due to slip rings and carbon brushes.
Lower overall efficiency when running with external rotor resistance inserted due to copper losses (I2R).
Lower power factor compared to squirrel cage induction motors.
Elevators, hoists, cranes, and lifts
Compressors and pumps
Printing presses, line shafts, and crushers
Elevators, compressors, and printing presses all demand high starting torque or adjustable speed control during startup.
Option A (Elevator) alone is incorrect because compressors and printing presses are also valid applications.
Option B (Compressor) alone is incorrect as elevators and printing presses also utilize slip ring induction motors.
Option C (Printing press) alone is incorrect as elevators and compressors share similar mechanical requirements.
D is correct тАФ Slip ring induction motors provide high starting torque and speed control, making them suitable for elevators, compressors, and printing presses.
Remember: Squirrel cage motors are preferred for constant speed and low starting torque applications, whereas slip ring (wound rotor) motors are chosen whenever high starting torque or speed control is required.