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In the very small ratting universal motor, Which of the following thing is not required?
Laminated Core
Commutator and Brushes
Compensating Winding
All of these
Compensating Winding
In very small-rated universal motors (typically rated below 100┬аW), compensating windings are not required because the armature reaction is negligible ┬╖ As the motor rating decreases, the armature current is very low, making cross-magnetizing effects and commutation issues minimal.
In very small-rated universal motors (typically rated below 100┬аW), compensating windings are not required because the armature reaction is negligible ┬╖ As the motor rating decreases, the armature current is very low, making cross-magnetizing effects and commutation issues minimal.
FaтАЛ=NaтАЛIaтАЛ тАФ Armature MMF (proportional to armature current)
ecтАЛ=LdtdIтАЛ тАФ Reactance voltage during commutation
Universal motors operate on both AC and DC supplies using a series-wound configuration ┬╖ In larger motors, armature reaction causes severe flux distortion and commutation sparkings, requiring compensating windings in phase opposition to cancel the armature field ┬╖ In small fractional horsepower motors, the weak armature flux (IaтАЛNaтАЛ) eliminates the need for compensation, simplifying motor design and reducing cost.
A laminated core is essential for operating on AC supply to minimize eddy current losses in both stator and rotor.
Commutator and brushes are always required to rectify AC or direct DC current to maintain unidirectional torque.
Compensating windings are used only in higher-rated universal motors (typically >100┬аW) to neutralize armature reaction and improve commutation.
Omitting the compensating winding reduces manufacturing cost, weight, and overall size of small appliances.
Reduces overall manufacturing cost and complexity.
Allows ultra-compact motor size for small appliances.
Reduces internal winding resistance and copper losses in low-power applications.
Higher sparking at brushes during high load conditions in uncompensated machines.
Slightly lower power factor under loaded conditions.
Food mixers and blenders
Handheld sewing machines
Portable electric drills
Hair dryers and vacuum cleaners
Option A (Laminated Core): Required to reduce eddy current losses caused by alternating flux on AC operation.
Option B (Commutator and Brushes): Required in all universal motors to reverse armature current direction periodically.
Compensating winding is placed in stator slots along the quadrature axis (Q-axis) in conductive or inductive arrangements in higher-rated motors.
C is correct тАФ Small-rated universal motors have very low armature current, rendering armature reaction negligible and eliminating the need for compensating windings.
In DC machines and higher-rated AC series motors, compensating windings are connected in series with the armature, whereas in small fractional HP universal motors, resistance commutation via high-resistance brushes is sufficient.