V curve and inverted v curve for synchronous generator alternator also v curve of alternator. V curve and inverted v curve are depicted below figure 1 figure 2 v curve is plotted between armature current and field current. Since the shape of these curves is similar to the letter v, thus they are called v curve of. A synchronous condenser or a synchronous compensator is a synchronous motor running without a mechanical load. When synchronous motor is is said to receive 100% excitation. Synchronous motor copyright 2004 kilowatt classroom, llc. V and inverted v curves of synchronous motor effect of change in excitation of synchronous motor. 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 vcurves and inverted vcurves of the 3phase synchronous motor have been drawn.
Vcurve of a synchronous shows its performance in terms of variation of machine armature current with field current when the load and input voltage to the is constant. You may do so in any reasonable manner, but not in. There are separate v curves for noload and fullload and sometimes the motor manufacturer publishes curves for 25%, 50%, and 75% load. Synchronous speed is directly proportinal to frequency,similar ti induction motors constant flux operation below base speed is achiecved by operating the synchronous motor with constant v f ratio. Since the shape of these curves is similar to the letter v, thus they are called v curve of synchronous motor. 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 using.
For drawing v curves and inverted v curves of synchronous motor following measuring instruments and accessories. The block diagram shows the drive electronics associated with a low voltage 12 v dc synchronous motor. Stator is connected top three phase supply through wattmeters and ammeter. For simplicity, the stator winding resistance rs has been neglected. Synchronous machines the inductance of the stator winding depends on the rotor position energy is stored in the inductance as the rotor moves, there is a change in the energy stored either energy is extracted from the magnetic field and becomes mechanical energy that is, its is a motor or energy is stored in the magnetic field and. What are v and inverted v curves of synchronous motor. Commons is a freely licensed media file repository. Synchronous machines 2 in this chapter, we concentrate on conventional synchronous machines whereas the brushless dc motors will be discussed later in a separate chapter. Stardelta starting of a three phase induction motor 10. V and inverted v curves of synchronous motor electrical. About this video what is vcurve in synchronous motor what is inverted vcurve in synchronous motor full explanation about under excitation, normal excitation, and over excitation in vcurves and. However, the rotor can be shifted in phase by angle.
Synchronous machine structures stator and rotor the armature winding of a conventional synchronous machine is almost invariably on the stator and is usually a three phase winding. Pradyumna pooskuru 18 downloads 124 views 229kb size. In case the field current is made more than its normal excitation, i. V and inverted v curves of synchronous motor free download as word doc. 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. The two wattmeter method is used to measure input power of motor. There are separate v curves for no load and full load and some. 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 inverted v curve. It can generate or absorb reactive voltampere var by varying the excitation of its field winding. The curve displayed the properties of a pn junction.
May 15, 2018 synchronous motor excitation refers to the dc supply given to rotor which is used to produce the required magnetic flux. Load test on single phase squirrel cage induction motor aim. V curve of a synchronous shows its performance in terms of variation of machine armature current with field current when the load and input voltage to the is constant. V curve and inverted v curve for synchronous generator alternator. Synchronous machines can also be used as motors, but they are usually built in very large sizes. Effect of field current changes on synchronous motor. What is the significance of v curve and inverted v curve. V and inverted v curves of three phase synchronous motor aim. For a constant load, if the power factor is plotted against various values of field exciting current, the curve formed is inverted v shape and called as inverted v curve.
The curves are related to the phasor diagram in fig. Dec 08, 2017 about this video what is v curve in synchronous motor what is inverted v curve in synchronous motor full explanation about under excitation, normal excitation, and over excitation in v curves and. Synchronous and asynchronous electromechanicalsystems dr. V curve of a synchronous motor v curve is a plot of the stator current versus field current for different constant loads. I have a curve that has taken from keithley 2450 sourcemeter. 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. Hence when the machine operates as a synchronous motor the emf phasor always lags the terminal voltage phasor by the load1torque angle. True synchronous motors are driven by sine waveforms. Exp1 performance of a threephase synchronous motor. Jun 04, 2015 construction of v curves the v curves of a synchornous motor show how armature current varies with its field current when motor inpu t is kept constant. A synrm rotor has neither a conducting short circuit cage as with the im, nor permanent magnets, nor a field excitation winding. A short course on synchronous machines and synchronous. 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.
When w and wm are converted into cycles per second or hz and revolutions per minute respectively, we have. Regulation of 3phase alternator by zpf and asa methods 9. The corre sponding induction motor im however, has slip losses and rotates only at 1475rpm for a chosen 30 kw example. Ee8401 syllabus electrical machines 2 regulation 2017 anna. Pdf ee6504 electrical machinesii emii books, lecture. Two or threephase drive may be used by supplying the appropriate number of windings in the stator. Ammeter reads the line current which is same as armature stator current.
Bh curve experiment manual pdf laboratory manual v and inverted v curves of a 3phase synchronous motor. One well known approach is the utilization of synchronous motors sm. Typically, the synchronous machine vcurves are provided by the manufacturer so that the user can determine the resulting operation under a given set of conditions. About this video what is vcurve in synchronous motor what is inverted vcurve in synchronous motor full explanation about under excitation. The synchronous motor operates at a precise synchronous speed, and hence is a constantspeed motor. This file is licensed under the creative commons attributionshare alike 3. The arms of the v are under and overexcited regimes which generate reactive power output. A short course on synchronous machines and synchronous condensers. V curve and inverted v curves are applicable for synchromous machine. Fig1 shows the variation of armature current and power factor with field current at no load, half load and full load conditions. The vcurve analysis and study of synchronous motors. Electromagnetic devices draw a magnetizing current from the a. The synchronous motor either run at synchronous speed or it will not run at all.
In this experiment two watt meter method is used to measure input power of motor. Sms with a 4pole rotor operated at 50hz rotate in synchronism with the supply at exactly 1500rpm. 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. Measurement of x1, x2 and xo of a synchronous generator and calculation of currents. At what load angle is power developed in a synchronous motor becomes its maximum value. A synchronous motor is a doubleexcited machine, its armature. Synchronous motor excitation refers to the dc supply given to rotor which is used to produce the required magnetic flux. A vcurve of a synchronous motor shows the relation between armature currents as ordinates and field currents as abscissas when the motor operates with a constant power input at rated terminal voltage.
What is the difference between iv curve and jv curve. Oct 29, 2016 bh curve experiment manual pdf laboratory manual v and inverted v curves of a 3phase synchronous motor. A synchronous motor starts as usual but fails to develop its full torque. Unlike the induction motor, whose operation always involves a lagging power factor, the synchronous motor possesses a variablepowerfactor. Vcurves and inverted vcurves of synchronous motor youtube. Construction of vcurves the v curves of a synchornous motor show how armature current varies with its field current when motor inpu t is kept constant. Synchronous condensor synchronous condensor is also known as synchronous compensator or synchronous phase modifier. To start induction motor by rotor resistance starter 8. Typically, the synchronous machine v curves are provided by the manufacturer so that the user can determine the resulting operation under a given set of conditions. To draw the v and inverted v curves of three phase synchronous motor. V curves and inverted vcurves of synchronous motor a synchronous motor is a doubleexcited machine, its armature winding is energized from an a. Armature current is obtained by dividing this vector. When the assembled motor is in operation, the stator windings are connected directly to the power source. 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.
When the synchronous machine is connected to infinite bus v, the rotor must turn at angular frequency. The synchronous motor v curves shown above illustrate the effect of excitation field amps on the armature stator amps and on system power factor. V and inverted v curves of synchronous motor effect of. Electrical machines expected mcq pdf 8 for coal india limited cil mt exam 2017. 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. Title of the paper 18pt times new roman, bold semantic scholar. Unit ii synchronous motor ee8401 syllabus electrical machines 2 principle of operation torque equation operation on infinite bus bars v and inverted v curves power input and power developed equations starting methods current loci for constant power input, constant excitation and constant power developedhunting. The bottom tip of the v is pure active power output from the machine. V curve and inverted v curve for synchronous generator alternator also v curve of. Synchronous machines 6 where w is the angular frequency of emf in electrical radians per second and wm the angular speed of the rotor in mechanical radians per second. Why doesnt the v curve of a synchronous motor touch the. Mar 25, 2018 v curve and inverted v curve for synchronous generator alternator also v curve of alternator. The ammeter is reading line current which is same as armature stator current. This magnetizing current lags the applied voltage by almost 900.
The vcurve is used to describe the power output of a synchronous machine with regard to the excitation current. Information from its description page there is shown below. Vcurves consider a synchronous motor operating at rated mechanical load examine the behavior as the excitation is varied mechanical power remains constant at unity power factor the motor current is at a minimum at unity power factor the total power equals the active power as excitation increases or decreases. The synchronous reluctance motor magnetic reluctance is the magnetic equivalent of the resistance in electrical. Synchronous motors controlled by variablespeed drives are. Synchronous machines rotation the axis of the field winding in the direction of the dc field is called the rotor direct axis or the daxis. Download link is provided and students can download the anna university ee6504 electrical machinesii em ii syllabus question bank lecture notes syllabus part a 2 marks with answers part b 16 marks question bank with answer, all the materials are listed below for the students to make use of it and score good maximum marks with our study materials.
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