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Which of the following single-phase motor can work on both AC or DC supply?
DC Series Motor
Repulsion Motor
Universal Motor
Shaded Pole Motor
Universal Motor
A Universal motor is a special type of series motor designed to operate on either AC or DC supply. It is essentially a DC series motor modified to minimize inductive reactance and eddy current losses, allowing it to perform effectively with both power sources.
A Universal motor is a special type of series motor designed to operate on either AC or DC supply. It is essentially a DC series motor modified to minimize inductive reactance and eddy current losses, allowing it to perform effectively with both power sources.
TтИЭ╬жIaтАЛ тАФ Basic motor torque principle
TтИЭIa2тАЛ тАФ Universal motor torque relation for series operation
When connected to an AC supply, the series-connected field and armature windings experience current reversal simultaneously, maintaining a unidirectional torque direction. To prevent excessive eddy current losses in the magnetic circuit when on AC, the stator poles and yoke are laminated. The torque produced is proportional to the square of the current, given by TтИЭI2.
Operates on both AC and DC sources.
Stator and rotor are connected in series.
Requires laminated core to reduce eddy current losses on AC.
High starting torque and high speed characteristics.
High power-to-weight ratio
Compact size
High speed capability
High maintenance due to commutator and brushes
Significant electromagnetic interference (EMI)
Noisy operation at high speeds
Vacuum cleaners
Food mixers
Portable drills
Sewing machines
The repulsion motor works on AC only by electromagnetic repulsion principle.
The DC series motor can technically run on AC but results in excessive sparking and overheating due to high inductance and eddy currents in a solid yoke.
C is correct тАФ The Universal motor is specifically engineered with laminated construction and series-wound characteristics to function efficiently on both AC and DC power supplies.
Always remember that while a DC series motor theoretically turns on AC, it will spark violently; the 'Universal Motor' is the practical, engineered version of this concept.