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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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The ______________ is modified DC Series motor.
Shaded Pole Motor
Repulsion Motor
Repulsion Induction Motor
Universal Motor
Universal Motor
Quick Summary: A Universal motor is essentially a modified DC series motor designed to operate on both AC and DC power supplies. It features a wound armature and field connected in series, allowing it to produce unidirectional torque regardless of the polarity of the supply voltage.
A Universal motor is essentially a modified DC series motor designed to operate on both AC and DC power supplies. It features a wound armature and field connected in series, allowing it to produce unidirectional torque regardless of the polarity of the supply voltage.
Td∝ΦIa — Basic torque equation for series machines
Pin=VIcosϕ — Power input equation
Since the field and armature are in series, reversing the supply polarity reverses the current in both simultaneously, keeping the torque direction constant. Modifications include a laminated stator core and compensating windings to reduce eddy current losses and improve commutation under AC conditions. The torque produced is proportional to the square of the current, which is a characteristic trait of series-wound machines.
Operates on both AC and DC sources.
Exhibits high starting torque similar to DC series motors.
Speed control is achieved using a thyristor or TRIAC-based chopper/dimmer circuit.
Laminated yoke is required to minimize eddy current loss in AC operation.
Very high speed capabilities
High starting torque
Compact and lightweight
Simple speed control
High noise and vibration
Short brush life due to sparking
Requires maintenance (brushes/commutator)
Radio frequency interference (RFI)
Mixers and blenders
Vacuum cleaners
Portable power tools (drills, saws)
Sewing machines
The armature and field windings must be connected in series to ensure the motor behaves as a series motor.
Option B (Repulsion Motor) works on the principle of electromagnetic repulsion between the stator and rotor fields, which is distinct from the series-conduction principle of the Universal Motor.
D is correct — The Universal Motor is specifically engineered with modifications like laminated magnetic circuits to function efficiently as a DC series motor on an AC supply.
Always remember that a Universal Motor's speed is inversely proportional to load torque; it can reach dangerously high 'runaway' speeds at no-load conditions.