The two wattmeter method is used to measure input power of motor. The synchronous reluctance motor magnetic reluctance is the magnetic equivalent of the resistance in electrical. 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. Synchronous motors controlled by variablespeed drives are. Fig1 shows the variation of armature current and power factor with field current at no load, half load and full load conditions. One well known approach is the utilization of synchronous motors sm. V curve of a synchronous motor v curve is a plot of the stator current versus field current for different constant loads.
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. Why doesnt the v curve of a synchronous motor touch the. The bottom tip of the v is pure active power output from the machine. 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. The curve displayed the properties of a pn junction. 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.
It can generate or absorb reactive voltampere var by varying the excitation of its field winding. The vcurve analysis and study of synchronous motors. 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. 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. V and inverted v curves of synchronous motor electrical. Sms with a 4pole rotor operated at 50hz rotate in synchronism with the supply at exactly 1500rpm.
V and inverted v curves of three phase synchronous motor aim. 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. Electrical machines expected mcq pdf 8 for coal india. 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. 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. When its load angle is equal to the impedance angle. About this video what is vcurve in synchronous motor what is inverted vcurve in synchronous motor full explanation about under excitation.
Effect of field current changes on synchronous motor. Vcurves and inverted vcurves of synchronous motor youtube. To conduct the load test on single phase squirrel cage induction motor and to draw the. At what load angle is power developed in a synchronous motor becomes its maximum value. A plot of bh where both b and h vary between a positive. Oct 29, 2016 bh curve experiment manual pdf laboratory manual v and inverted v curves of a 3phase synchronous motor. Measurement of x1, x2 and xo of a synchronous generator and calculation of currents. A synchronous motor starts as usual but fails to develop its full torque. When the assembled motor is in operation, the stator windings are connected directly to the power source. Information from its description page there is shown below. 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. 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.
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. A synrm rotor has neither a conducting short circuit cage as with the im, nor permanent magnets, nor a field excitation winding. Instead, the magnetic principle of reluctance is utilized. The arms of the v are under and overexcited regimes which generate reactive power output.
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. Ee8401 syllabus electrical machines 2 regulation 2017 anna. V curves and inverted v curves of synchronous motor. Synchronous condensor synchronous condensor is also known as synchronous compensator or synchronous phase modifier. To draw the v and inverted v curves of three phase synchronous motor. The synchronous motor either run at synchronous speed or it will not run at all. V curve and inverted v curve are depicted below figure 1 figure 2 v curve is plotted between armature current and field current. V curve and inverted v curve for synchronous generator. Since the shape of these curves is similar to the letter v, thus they are called v curve of. The curves are related to the phasor diagram in fig. Since the shape of these curves is similar to the letter v, thus they are called v curve of synchronous motor. This magnetizing current lags the applied voltage by almost 900. Stator is connected top three phase supply through wattmeters and ammeter.
Stardelta starting of a three phase induction motor 10. A synchronous condenser or a synchronous compensator is a synchronous motor running without a mechanical load. To start induction motor by rotor resistance starter 8. Ammeter reads the line current which is same as armature stator current.
True synchronous motors are driven by sine waveforms. 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. V curve and inverted v curve for synchronous generator alternator also v curve of. Hence when the machine operates as a synchronous motor the emf phasor always lags the terminal voltage phasor by the load1torque angle. Title of the paper 18pt times new roman, bold semantic scholar. The synchronous motor v curves shown above illustrate the effect of excitation field amps on the armature stator amps and on system power factor. You may do so in any reasonable manner, but not in. When the synchronous machine is connected to infinite bus v, the rotor must turn at angular frequency.
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. For simplicity, the stator winding resistance rs has been neglected. Synchronous and asynchronous electricmotors the electric motor is an electromechanical continuous energy conversion equipment that converts electrical energy into electrical energy mechanical energy. Pdf ee6504 electrical machinesii emii books, lecture. 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. V curve and inverted v curve for synchronous generator alternator also v curve of alternator. Electrical machines expected mcq pdf 8 for coal india limited cil mt exam 2017. 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. 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 w and wm are converted into cycles per second or hz and revolutions per minute respectively, we have. When synchronous motor is is said to receive 100% excitation.
Two or threephase drive may be used by supplying the appropriate number of windings in the stator. V and inverted v curves of synchronous motor free download as word doc. 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. Commons is a freely licensed media file repository. 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. 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. The block diagram shows the drive electronics associated with a low voltage 12 v dc synchronous motor. Electromagnetic devices draw a magnetizing current from the a. Bh curve experiment manual pdf laboratory manual v and inverted v curves of a 3phase synchronous motor. There are separate v curves for noload and fullload and sometimes the motor manufacturer publishes curves for 25%, 50%, and 75% load. I have a curve that has taken from keithley 2450 sourcemeter. What is the difference between iv curve and jv curve. In this experiment two watt meter method is used to measure input power of motor. What is the significance of v curve and inverted v curve.
The vcurves and inverted vcurves of the 3phase synchronous motor have been drawn. V curve and inverted v curve for synchronous generator alternator. 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. The vcurve analysis and study of synchronous motors using. This file is licensed under the creative commons attributionshare alike 3. May 15, 2018 synchronous motor excitation refers to the dc supply given to rotor which is used to produce the required magnetic flux. Pradyumna pooskuru 18 downloads 124 views 229kb size. The vcurve is used to describe the power output of a synchronous machine with regard to the excitation current.
Synchronous motor copyright 2004 kilowatt classroom, llc. The synchronous motor operates at a precise synchronous speed, and hence is a constantspeed motor. Mar 25, 2018 v curve and inverted v curve for synchronous generator alternator also v curve of alternator. V and inverted v curves of synchronous motor effect of change in excitation of synchronous motor.
A short course on synchronous machines and synchronous condensers. Unlike the induction motor, whose operation always involves a lagging power factor, the synchronous motor possesses a variablepowerfactor. V and inverted v curves of synchronous motor effect of. Synchronous machines can also be used as motors, but they are usually built in very large sizes. Exp1 performance of a threephase synchronous motor.
V curve and inverted v curves are applicable for synchromous machine. Load test on single phase squirrel cage induction motor aim. The corre sponding induction motor im however, has slip losses and rotates only at 1475rpm for a chosen 30 kw example. There are separate v curves for no load and full load and some. 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. For drawing v curves and inverted v curves of synchronous motor following measuring instruments and accessories. Regulation of 3phase alternator by zpf and asa methods 9. The ammeter is reading line current which is same as armature stator current. However, the rotor can be shifted in phase by angle. In case the field current is made more than its normal excitation, i.
The steadystate characteristics of a synchronous motor represented by phasor diagrams are shown as function of the excitation voltage e. 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. Synchronous motor excitation refers to the dc supply given to rotor which is used to produce the required magnetic flux. What are v and inverted v curves of synchronous motor.