The motor vcurves describe the relationships among field current, armature current, load and power factor. The v curve is used to describe the power output of a synchronous machine with regard to the excitation current. Dec 08, 2017 what is inverted v curve in synchronous motor full explanation about under excitation, normal excitation, and over excitation in v curves and inverted v curves relation between field current and. The arms of the v are under and overexcited regimes which generate reactive power output. V curve and inverted v curve are depicted below figure 1 figure 2 v curve is plotted between armature current and field current. In other words, the function of this magnetizing current or lagging va drawn by the electromagnetic device is to set up the. This curve is popularly known as v curve of generator connected to infinite bus. Stator is connected top three phase supply through wattmeters and ammeter.
The analysis shows that depending upon the mode employed the machine can be made to possess shunt, series or mixed characteristic. E b is equal in magnitude to applied voltage v is known as 100% excitation. The input power to a threephase synchronous motor is given by p 3 v i cos. Hence when the machine operates as a synchronous motor the emf phasor always lags the terminal voltage phasor by the load1torque angle. The purpose of the curve is to show the variation in the magnitude of the armature current as the excitation voltage of the machine is varied. When its load angle is equal to the impedance angle. To achieve this a suitable theoretical model is essential, thus a simple but complete motor model is developed. Synchronous motor is the heart of the power system.
For drawing v curves and inverted v curves of synchronous motor following measuring instruments. A family of vcurves may be obtained for a given motor by observing the above relations for a number of values of constant power inputs. Such curves are called v curves of synchronous motor. Unlike the induction motor, whose operation always involves a lagging power factor, the synchronous motor possesses a variablepowerfactor. The block uses the threephase input voltages to regulate the individual phase currents, allowing control of the motor torque or speed. 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. In this video covered v curve of synchronous motor and all important fact for competitive exam such as uppcl ssc railway bhel bel iocl ntpc etc electrical je this channel is fully help full for. Difference between synchronous and asynchronous motor. The two wattmeter method is used to measure input power of motor. Jun 04, 2015 effect of excitation on armature current and power factor the value of excitation for which back e. Commons is a freely licensed media file repository. By controlling the field current, reactive power supplied to the motor can be controlled. The loading of the machine determines which of the v curves the machine is operating on. The ammeter is reading line current which is same as armature stator current.
The synchronous motor operates at a precise synchronous speed, and hence is a constantspeed motor. A general overview of line start synchronous machines is first. Eb is equal in magnitude to applied voltage v is known as 100% excitation. You may do so in any reasonable manner, but not in. As it can be seen in the equations 1 and 2 the terms p y q and p y d transform themselves in p y mq and p y mq respectively when the saturation in the. This magnetizing current lags by almost 90 o to the supply voltage. The graph plotted between the armature current ia and field current if at no load the curve is obtained known as v curve. Permanent magnets are rigidly fixed to the rotating axis to create a constant rotor flux. The hunting in a synchronous motor takes place when. What does each part of the v curve of a synchronous motor mean. Set of vcurves can be drawn for the same motor, each curve corresponding to particular outputinput power held constant. Since the shape of these curves is similar to the letter v, thus they are called v curve of. So synchronous motor can be used as synchronous generator. This makes lagging power factor synchronous motor to operate partly as an induction motor at full load and this is the reason for the increased load emf as high as 575 volts by measurement from fig.
Torquespeed curve the torque developed by a conventional 3phase motor depends on its speed but the relation between the two cannot be represented by a simple equation. Synchronous motors introduction it may be recalled that a d. Prior to understanding this synchronous motor excitation, it should be remembered that any electromagnetic device must draw a magnetizing current from the ac source to produce the required working flux. Pdf effects of vskew on the torque characteristic in. This winding is spatially distributed for polyphase ac current.
Stopping the synchronous motor example a 1500 kw, 4600 v, 600 rpm motor is stopped by using the shortcircuit method e0 2400, xs 16. The bottom tip of the v is pure active power output from the machine. Since the shape of these curves is similar to the letter v, thus they are called v curve of synchronous motor. As the name implies, a synchronous motor runs at synchronous speed n s 120fp i. V curve of a synchronous motor v curve is a plot of the stator current versus field current for different constant loads. Jun 02, 2015 torquespeed curve the torque developed by a conventional 3phase motor depends on its speed but the relation between the two cannot be represented by a simple equation. This magnetizing current lags the applied voltage by almost 900. In like manner, an alternator may operate as a motor by connecting its armature winding to a 3phase supply.
Using two axis model the steady state characteristics of a voltage controlled synchronous motor drive are investigated for different modes of operation based on signal flow graph technique. In recent years, with the rapid development of electric power electronics technical, rare earth permanent magnetic materials and the increasingly sophisticated. To repeat the above, with synchronous motor loaded to half the full load and 34 the full load. V curvescurve ofreactive currentexpression for reactive current. The motor v curves describe the relationships among field current, armature current, load and power factor. This armature creates a rotating magnetic field inside the motor. If excitation is varied from very low under excitation to very high over excitation value, then current ia decreases, becomes minimum at unity p. The curves are related to the phasor diagram in fig. What is the difference between synchronous motor and.
Why doesnt the v curve of a synchronous motor touch the. About this video what is vcurve in synchronous motor what is inverted vcurve in synchronous motor full explanation about under excitation. V curves are useful for adjusting the field current. Configuration and performance of electrical vehicles, traction motor haracteristics, tractive effort. At what load angle is power developed in a synchronous motor becomes its maximum value. We will now discuss what happens when motor is either overexcited or underexicted although we have already touched this point in art. Why doesnt the v curve of a synchronous motor touch the d. Vector control of permanent magnet synchronous motor. A synchronous does not possess starting torque but once brought near. Closing q and energising m, ci and c 3 causes pony motor to drive synchronous motor up to near synchronous speed. Synchronous machines have parabolic type characteristics. Energising c2 at the same time as deenergising o will cause the rotor of the synchronous motor to reach. Search wegsynchronousmotors50019091brochureenglish. Synchronous machines can also be used as motors, but they are usually built in very large sizes.
Inverted v curves a family of curves can be obtained by plotting the power factor versus field current at a constant load of synchronous motor. Sensorless field oriented control of 3phasepermanent. Vector diagram correlation of leading and lagging power. Pdf new linestarting method of synchronous motors not. Threephase interior permanent magnet synchronous motor. Information from its description page there is shown below. V and inverted v curves of synchronous motor electrical. Pony motor u2 synchronous motor the correct operation of the above power circuit is as follows. But initial lagging current becomes unity and then becomes leading. A synchronous electric motor is an ac motor distinguished by a rotor spinning with coils passing magnets at the same rate as the alternating current and resulting magnetic field which drives it. Yes, usually, diesel generator uses ac synchronous generator. In this item a synchronous machine dynamic mathematical model is developed to included the saturation using the equations 1 to 5 and also the machine daxis and qaxis magnetizing curves.
If the v curves at different load conditions are plotted and points on different curves having same p. V curves and inverted v curves of synchronous motor. Vector control of pm synchronous motor drive system using. Effects of vskew on the torque characteristic in permanent magnet synchronous motor article pdf available december 20 with 1,623 reads how we measure reads. Armature current is obtained by dividing this vector. On the performance characteristics of a synchronous motor. The stator is the outer shell of the motor, which carries the armature winding. Title of the paper 18pt times new roman, bold semantic scholar. Help explain the v curves of a synchronous motor yahoo. May 15, 2018 synchronous motor excitation refers to the dc supply given to rotor which is used to produce the required magnetic flux.
An original linestarting method for a synchronous machines, which do not have damping windings, is investigated in this paper. If graph of armature current drawn by synchronous motor is against field current is plotted then the resulted graph is known as a. The graph plotted between the armature current i a and field current i f at no load the curve is obtained known as v curve. Jan 27, 2012 help explain the v curves of a synchronous motor i am really confused how the power factor is changed in synchronous machines please explain how the v curve works. Effect of excitation on armature current and power factor. There are separate v curves for noload and fullload and sometimes the motor manufacturer publishes curves for 25%, 50%, and 75% load. A threephasesynchronous motor with a one permanent magnet pair pole rotor 3 synchronous motor operation synchronous motor construction.
In synchronous motors performance characteristics obtained by v curves and inverted vcurves. A synchronous motor is composed of the following parts. In this diagram, t represents the nominal fullload torque of the motor. The input voltages are assumed to be quasi square wave. For the love of physics walter lewin may 16, 2011 duration. The vcurve analysis and study of synchronous motors using. Electromagnetic devices draw a magnetizing current from the a. A 3 phase, 400 v, 50 hz synchronous motor has fixed excitation. V curve of generator is a plot of variation of armature current with the change in field current. V curv of synchronous motor in hindi inverted v curve of.
In fact, a given synchronous machine may be used, at least theoretically, as an alternator, when driven mechanically or as a motor, when driven electrically, just as in the case of d. Adjust the field excitation of the synchronous machine so that about rated voltage 400v, ll is obtained. Vcurve of a synchronous machine shows its performance in terms of variation of armature current with field current when the load and input voltage to. The vcurve is used to describe the power output of a synchronous machine with regard to the excitation current. Another way of saying this is that it has zero slip under usual operating conditions. Vector control of pm synchronous motor drive system using hysteresis current controller 1rajesh p. Synchronous machine fild current calculation taking into. What are v and inverted v curves of synchronous motor.
It is seen that vector difference of eb and v is zero and so is the armature current. After having the concept behind the three cases discussed, it is better to plot a curve between field current and armature current. In fact, at very low power levels the synchronous motor can be. An induction generator or asynchronous generator is a type of alternating current ac electrical generator that uses the prin. It is easier to show the relationship in the form of a curve fig. The steadystate characteristics of a synchronous motor represented by phasor diagrams are shown as function of the excitation voltage e. V curve and inverted v curves are applicable for synchromous machine. It is a kind of component that combines rotation and static, electromagnetic change and mechanical motion t. Vcurves and inverted vcurves of synchronous motor youtube. For a given level of real power transmission, the position on the vcurve is controlled by the magnitude of the field current. Help explain the v curves of a synchronous motor i am really confused how the power factor is changed in synchronous machines please explain how the v curve works. What is the significance of v curve and inverted v curve. It is important to state here that all synchronous motors do start as induction motors but.
Synchronous motor, like induction motor ie asynchronous motors, is a common ac motor. For a given level of real power transmission, the position on the v curve is controlled by the magnitude of the field current. Highperformance variablespeed motor drives are often constructed using a permanentmagnet synchronous motor. Mar 09, 2017 for the love of physics walter lewin may 16, 2011 duration. Synchronous motor characteristics v curves the steadystate characteristics of a synchronous motor represented by phasor diagrams are shown as function of the excitation voltage e. The vcurve analysis and study of synchronous motors. Synchronous reluctance machine design 1 1 introduction the purpose of this report is to present information necessary for developing a suitable synchronous reluctance motor synrm rotor geometry design procedure. Vector control of permanent magnet synchronous motor based on. V curves for a synchronous motor represent relation between.
The interior pmsm block implements a threephase interior permanent magnet synchronous motor pmsm with sinusoidal back electromotive force. A synchronous motor is a doubleexcited machine, its armature. One of the major and unique characteristics of this motor is that it can be operated at any electrical power factor leading, lagging or unity and this feature is based on the excitation of the synchronous motor. The synchronous machine synchronous ac machines find application as motors in constant speed applications and, when interfaced to the power source with a variablefrequency converter system, in variablespeed applications. This file is licensed under the creative commons attributionshare alike 3. Inverted v curve excitation vs power factor the synchronous motor v curves shown above illustrate the effect of excitation field amps on the armature stator amps and on system power factor. Permanent magnet synchronous motor pmsm has better dynamic performance, smaller size and higher efficiency.