Difference Between Synchronous and Asynchronous Motor

The Difference Between Synchronous and Asynchronous Motor are explained considering factors like its type, slip, requirement of additional power source, requirement of slip ring and brushes, their cost, efficiency, power factor, current supply, speed, self starting, effect in torque because of change in voltage, their operational speed and various applications of both Synchronous and Asynchronous motor.

Difference Between Synchronous and Asynchronous Motor are explained below in the tabulated form.

BASISSYNCHRONOUS MOTORASYNCHRONOUS MOTOR
DefinitionSynchronous motor is a machine whose rotor speed and the speed of the stator magnetic field is equal.
N= NS = 120f/P
Asynchronous motor is a machine whose rotor rotates at the speed less than the synchronous speed.
N < NS
Type Brushless motor, Variable Reluctance Motor, Switched Reluctance Motor and Hysteresis motor are the synchronous motor.AC Induction Motor is known as the Asynchronous Motor.
SlipDoes not have slip. The value of slip is zero.Have slip therefore the value of slip is not equal to zero.
Additional power sourceIt requires an additional DC power source to initially rotate the rotor near to the synchronous speed.It does not require any additional starting source.
Slip ring and brushesSlip ring and brushes are requiredSlip ring and brushes are not required.
CostSynchronous motor is costly as compared to Asynchronous motorLess costly
EfficiencyEfficiency is greater than Asynchronous motor.Less efficient
Power factorBy changing excitation the power factor can be adjusted accordingly as lagging, leading or unity.Asynchronous motor runs only at a lagging power factor.
Current supplyCurrent is given to the rotor of the synchronous motorThe rotor of Asynchronous motor does not require any current.
SpeedThe Speed of the motor does not depend on the variation in the load. It is constant.The Speed of the Asynchronous motor decreases with the increasing load.
Self startingSynchronous motor is not self startingIt is self starting
Affect in torque Change in applied voltage does not affect the torque of the synchronous motorChange in applied voltage does affect the torque of the Asynchronous motor
Operational speedThey operate smoothly and relatively good at low speed that is below 300 rpm.Above 600 rpm speed motor operation is excellent.
ApplicationsSynchronous motors are used in Power stations, manufacturing industries etc. it is also used as voltage controller.Used in Centrifugal pumps and fans, blowers, paper and textile mills, compressors and lifts. etc

Synchronous motor is a motor that operates at synchronous speed, i.e. speed of the rotor is equal to the stator speed of the motor. It follows the relation N = NS = 120f/P, where N is the rotor speed and Ns is the synchronous speed.

Asynchronous motor is an AC Induction motor. The rotor of the Asynchronous motor rotates at the speed less than the synchronous speed, i.e. N < NS

The detail explanation of the Difference Between Synchronous and Asynchronous Motor is given below.

  • Synchronous motor is a machine whose rotor speed and the speed of the stator magnetic field is equal. Asynchronous motor is a machine whose rotor rotates at the speed less than the synchronous speed.
  • Brushless motor, Variable Reluctance Motor, Switched Reluctance Motor and Hysteresis motor are the synchronous motor. AC Induction Motor is known as the Asynchronous Motor.
  • Synchronous motor does not have slip. The value of slip is zero. Asynchronous motor has slip therefore the value of slip is not equal to zero.
  • Synchronous motor requires an additional DC power source to initially rotate the rotor near to the synchronous speed. Asynchronous motor does not require any additional starting source.
  • Slip ring and brushes are required in synchronous motor, whereas Asynchronous motor does not require Slip ring and brushes. Only wound type Induction motor requires both slip ring and brushes.
  • Synchronous motor is costly as compared to Asynchronous motor.
  • Efficiency of Synchronous motor is greater than Asynchronous motor.
  • By changing excitation the power factor of the Synchronous motor can be adjusted accordingly as lagging, leading or unity, whereas Asynchronous motor runs only at a lagging power factor.
  • Current is given to the rotor of the synchronous motor. The rotor of Asynchronous motor does not require any current.
  • The Speed of the Synchronous motor does not depend on the variation in the load. It is constant. The Speed of the Asynchronous motor decreases with the increasing load.
  • Synchronous motor is not self starting, whereas Asynchronous is self starting.
  • Change in applied voltage does not affect the torque of the synchronous motor, whereas it affect the torque of the Asynchronous motor.
  • Synchronous motor operates smoothly and relatively good at low speed that is below 300 rpm, whereas above 600 rpm speed Asynchronous motor operation is excellent. Asynchronous motors are used in Centrifugal pumps and fans, blowers, paper and textile mills, compressors and lifts. etc
  • The various applications of the Synchronous motor are that it is used in Power stations, manufacturing industries etc. It is also used as voltage controller.

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