What is the difference between asynchronous and synchronous motors

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 rpm, whereas above rpm speed Asynchronous motor operation is excellent. Asynchronous motors are used in Centrifugal pumps and fans, blowers, paper and textile mills, compressors and lifts.

It is also used as voltage controller. Leave a Comment Cancel Reply Your email address will not be published. Synchronous motors require a DC power source for the rotor excitation. Synchronous motors require slip rings and brushes to supply rotor excitation. Induction motors dont require slip rings, but some induction motors have them for soft starting or speed control. Synchronous motors require rotor windings while induction motors are most often constructed with conduction bars in the rotor that are shorted together at the ends to form a squirrel cage.

Synchronous motors require a starting mechanism in addition to the mode of operation that is in effect once they reach synchronous speed. Three phase induction motors can start by simply applying power, but single phase motors require an additional starting circuit.

The power factor of a synchronous motor can be adjusted to be lagging, unity or leading while induction motors must always operate with a lagging power factor. Synchronous motors are generally more efficient that induction motors. Synchronous motors can be constructed with permanent magnets in the rotor eliminating the slip rings, rotor windings, DC excitation system and power factor adjustability. Synchronous motors are usually built only is sizes larger than about Hp kW because of their cost and complexity.

However, permanent magnet synchronous motors and electronically controlled permanent synchronous motors called brushless DC motors are available in smaller sizes. As the speed of the water turbine is slow hence more number of poles are required to attain the frequency. Therefore Salient pole machines will have typically number of poles will be between 4 to Cheaper compared to cylindrical rotor machines for speeds below rpm.

Causes excessive windage losses Flux distribution is not uniform due to the presence of salient poles, hence emf waveform generated is not good compared to cylindrical machine Salient Pole Synchronous Generators are employed in Hydro-Power plants. Non-Salient pole Synchronous Alternator: Non-Salient pole generators will have smaller diameter and longer axial length They are used for High speed operation typically speed will be and rpm Better in dynamic balancing because of absence of salient poles.

Less windage loss Robust construction and noiseless operation Nearly sinusoidal flux distribution around the periphery, therefore gives a better emf waveform than salient pole machine No need to provide damper windings except in special case to assist the synchronising because the field poles themselves acts as efficient dampers.

Open navigation menu. Close suggestions Search Search. User Settings. Skip carousel. Carousel Previous. Carousel Next. What is Scribd? Uploaded by Shiva Kumar Reddy. Document Information click to expand document information Description: we could get some idea about the synchros and asynchros machines.

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Flag for inappropriate content. Download now. For Later. Related titles. Carousel Previous Carousel Next. Jump to Page. Search inside document. The difference between asynchronous and synchronous motors The increasing importance of energy efficiency has brought electric motor makers to promote a variety of schemes that improve motor performance. Christie Cohen. Gopinath B L Naidu. Emil Alturk. Ursula Johnson. Donesh Varshney. Andrew Nibungco. Reza P. Ankesh Kapil. Does anybody have any knowledge on the topic?

I know permanent magnet motors are by themselves a different animal, but still, it is synchronous. Good article,but you did not mention about the fact that a asynchronous can never attain syn. Conversely,torque rises as speed drops,due to increased magnetic field in rotor.

Starting torque is approx. For example,electric cars,forklifts,motorcycles,mills,fans,pumps etc.. Electrical Equipment. Check it below: The following information deals with the general working principles of Synchronous and Asynchronous motors, their advantages and where are they normally used and what can be achieved using each of these motors.

Let us first concentrate on their working principles… Synchronous and Asynchronous Motors — Working Principles Synchronous Motors This is a typical AC electrical motor that is capable of producing synchronous speeds.

Asynchronous Motors The working principle of asynchronous motors is almost same as to that of synchronous motors except that it has no external exciter connected to it. But, the speed of an asynchronous motor reduces with the increase in the load. Synchronous motor can be operated at a wide range of power factors, both lagging and leading, whereas asynchronous motor always runs with a lagging p.

Synchronous motor is not self-starting, where as an asynchronous motor can be self-started. C excitation is required for synchronous motor to start, but an asynchronous motor does not require any external excitation to run. Synchronous motors are usually expensive and complicated when compared to the asynchronous motors which less expensive and user friendly. Synchronous motors are good for especially good for low-speed drives below rpm because their power factor can always be adjusted to 1.