A synchronous motor is one in which the rotor normally rotates at the same speed as the revolving field in the machine. However, in this case, the rotor has its own field produced by a dc current flowing through the rotor winding. A synchronous motor is an ac motor wherein, at steady state, the rotation of the shaft is synchronized with the frequency of the supplied current. The hysteresis motor, not having definite poles on the rotor, will lock in phase in an infinite num ber of positions with respect to. When the stator p of motor is connected to a threephase supply and driven up to its rated. Synchronous and asynchronous electricmotors the electric motor is an electromechanical continuous energy conversion equipment that converts electrical energy into electrical energy mechanical energy. Stator poles rotate at the synchronous speed ns when fed with a three phase supply. These are the most frequently used motors because electrical power is normally supplied as alternating current. Induction motor seminar ppt, pdf report study mafia. The exciter rotor supplies the necessary power to the motor excitation winding through a rotating, threephase. Three phase induction motor operates on induction principle. Synchronous and asynchronous electromechanicalsystems dr. Permanent magnet motors 2 permanent magnet motors there are primarily two types of threephasepermanent magnet synchronous motors. A 3phase supply is given to the armature of synchronous motor, produces a rotating magnetic field.
As the name suggests, this motor runs at a constant speed from no load to full load in synchronism with line frequency. Three phase motors are selfstarting except synchronous motors. The exciter generators 3phase output is rectified to dc by a 3phase rectifier. Today, the 3phase synchronous motor is used mostly in highly dynamic applications. Of synchronous machines the synchronous electrical generator also called alternator belongs to the family of electric rotating machines. Now before knowing, how the synchronous motors are started, we should know why they are not self started. It is worth noting that magnitude of e b does not change, only its phase changes. Synchronous motors contain multiphase ac electromagnets on the stator of the motor that create a magnetic field which rotates in time with the oscillations of the line. Synchronous motors i reluctance motor ii hysteresis motor. This is possible because the excitation of the synchronous motor can be adjusted as per the requirement. Based on the type of input we have classified it into single phase and 3 phase motors.
Free download induction motor seminar ppt, pdf report. Conversion to mechanical power by motors pumps, fans, hvac, refrigeration compressors. Three phase synchronous machines operated as generators mostly generate threephase power. Pdf balanced operation of three phase synchronous motors has been dealt with extensively in the literature. Lecture 6 three phase induction motors cairo university. Pdf balanced operation of three phase synchronous motors. Small multiphase synchronous motors may be started by ramping the drive frequency from. Highhorsepower synchronous ac motors, while more expensive than threephase induction motors, have two additional qualities. In three phase system, induction and synchronous motors are used. When threephase electric conductors are placed in certain geometrical positions i. As the name implies, a synchronous motor runs at synchronous speed ns 120fp i.
The working of the threephase induction motor is based on the principle of electromagnetic induction. A synchronous motor is a constant speed machine, which always rotates with zero speed at a synchronous speed, which is dependent on frequency and the. Despite the higher initial cost, they may be worthwhile in the long run because they are more energy efficient than other types of motors. As with a three phase induction motor, synchronous motor rotation is changed by reversing any two stator leads. Other members of the family are the directcurrent dc motor or generator, the induction motor or generator, and a number of derivatives of all these three. The rotor needs to be rotated at a speed near to the synchronous speed during starting. The stator is similar to that of an induction machine consisting of a cylindrical iron frame with windings, usually threephase, located in slots around the inner periphery. Generally, it is known as the asynchronous motor because its running speed is less than its synchronous speed. The rotor of a synchronous machine is a large electromagnet.
Differences between synchronous motor and induction motor. Distributed three phase windings the stator of a synchronous machine consists of a laminated electrical steel core and a three phase winding. The synchronous motors are utilized in industrial applications that require constant speed rotation. Three phase power is transmitted and distributed more economical than single phase power. These motors contain multiphase ac electromagnets on the stator of the motor that create a. The synchronous electrical generator also called alternator belongs to the.
In an induction motor the rotor must have some slip. The threephase systems online electrical course covers threephase motor principles for induction, synchronous, and multispeed dualvoltage motors. Synchronous motors are threephase ac motors which run at synchronous speed. Applications of three phase synchronous motor electrical.
The per phase power development in a synchronous machine is as under. A motor fitted with rotor windings requires brushes to obtain its current supply and generate rotor flux. Three phase winding is given a three phase ac supply. Synchronous motor copyright 2004 kilowatt classroom, llc. The stator is excited by the threephase supply, and the rotor is excited by the dc supply.
Threephase synchronous motors find their major application in industrial situations where there is a large, reasonably steady mechanical load, usually in excess of 300 kilowatts, and where the ability to operate at leading power factor is of value. Whats the difference between asynchronous and synchronous. Other articles where threephase synchronous motor is discussed. Synchronous motors for constantspeed 10 applications 4. Ac induction motors are also the most common motors used in main powered home appliances. Working principle of a synchronous motor the stator and the rotor are the two main parts of the synchronous motor. When a 3 phase electric conductors are placed in a certain geometrical positions. As we already know that synchronous motor is not selfstarting and we already discussed wh y the synchronous motor is not selfstarting. Induction motor does not require any extra dc excitation source. The synchronous motors are often used as a power factor correction device, phase advancers and phase modifiers for voltage regulation of the transmission lines. A synchronous motor has a special rotor construction that lets it rotate at the same speed that is, in synchronization with the stator field. Gives recommended maintenance practices for large ac motors. However, synchronous motors are not used so much because they run at constant speed i.
Threephase asynchronous motors da ul motor with ul approval mains voltage motor voltage 5 400v 360v x special voltage nominal speed e. Almost 80% of the mechanical power used by industries is provided by three phase induction motors because of its simple and rugged construction, low cost, good operating characteristics, absence of commutator and good speed regulation. The electromagnetic armature is only energized after the rotor is brought up to near synchronous speed. It is less costly in certain kw and speed ranges, i. The theoretical standard of this project was reached successfully by comparing its main features to that of already existing synchronous motors having similar datasheets. The stator is the stationary part of the motor and rotor is their rotating part. A 3phase pm synchronous motor was designed in accordance with the requirements and objectives of the thesis. Difference between synchronous motor and induction motor. It usually runs at higher efficiencies, especially in lowspeed unity power factor. The answer can be given as, when 3 phase supply is given to the stator, there is a rotating magnetic flux which rotates at synchronous speed, and if the rotor is also given dc supply, rotor acts as a magnetic flux which rotates at synchronous speed, and if the rotor is also given dc supply. Electrical motors are an electromechanical device that converts electrical energy to mechanical energy. A threephase stator similar to that of an induction motor.
When the load on induction motor increases its speed decreases. The threephase synchronous machine has two main windings. A synchronous electric motor is an ac motor in which, at steady state, the rotation of the shaft is synchronized with the frequency of the supply current. This paper presents load characteristics of a threephase induction motor model core calculated with the. If done so, the rotor poles get magnetically coupled with the rotating stator poles, and thus the rotor starts rotating at the synchronous speed. Induction motor always operates at lagging power factor. Induction motor always run less than synchronous speed. Covers principles of threephase motor starters, part winding, reversing, jogging, alternator principles and operation. Working principle of a synchronous motor circuit globe.
The threephase induction motor is the extensively used for various kinds of industrial drives. Most synchronous motors are rated between 150 kw and 15 kw and run at speeds from 150 to 1800 rpm. The three phase induction motor is the most widely used electrical motor. Sensorless field oriented control of 3phase permanent. When threephase stator winding of an induction motor is energized from a 3 phase supply, a rotating magnetic field is set up which rotates around the stator at synchronous speed ns. A portion of rotating magnetic field in a threephase. An induction motor can be defined as the ac electric motor device in which a power source fed by the alternating current with the help of a primary winding. Rotor windings are not fed by electricity, currents flow through rotor due to induction process. Synchronous motors are three phase ac motors which run at synchronous speed, without slip.
This rotor field tends to align itself along with the rotating magnetic field produced by. The threephase synchronous motor is a unique and specialized motor. Singlephase induction motors are usually twopole or fourpole, rated at 2 hp or less, while slower and larger motor can be. Exciter with alternating current supply on the stator. Now a rotating magnetic field is produced which is rotating at synchronous speed ns rpm. Differences between three phase induction machine and synchronous machine three phase induction machine synchronous machine stator phase are star connected only stator phases either star or delta connected rotor windings are fed by dc source.
Three phase motors have an absolute uniform continuous torque, whereas, single phase motors have pulsating torque. Advantages of 3 phase induction motor generally easy to build and cheaper than corresponding dc or synchronous motors induction motor is robust. Synchronous motors are often directcoupled to the load and may share a. As in squirrelcage induction motors, the speed of a synchronous motor is determined by the number of pairs of poles and the line frequency.