The vcurve analysis and study of synchronous motors. Stardelta starting of a three phase induction motor 10. A plot of bh where both b and h vary between a positive. Vcurves, inverted vcurves, phasor diagram, starting of synchronous motors. What are v and inverted v curves of synchronous motor. 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.
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. 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. Effect of excitation on armature current and power factor. V and inverted v curves of synchronous motor electrical.
The synchronous motor either run at synchronous speed or it will not run at all. 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. Regulation of 3phase alternator by zpf and asa methods 9. Vcurves and inverted vcurves of synchronous motor youtube. When its load angle is equal to the impedance angle. Stator is connected top three phase supply through wattmeters and ammeter. Hence when the machine operates as a synchronous motor the emf phasor always lags the terminal voltage phasor by the load1torque angle. Synchronous motor copyright 2004 kilowatt classroom, llc.
Unlike the induction motor, the synchronous motor is connected to two electrical systems. 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. In iv measurement there is no need to consider of area aand hence the curve is i ampvs v volts. If the v curves at different load conditions are plotted and points on different curves having same p. Vcurves and inverted vcurves of synchronous motor a synchronous motor is a doubleexcited machine, its armature winding is energized from an a. 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. It can generate or absorb reactive voltampere var by varying the excitation of its field winding. Explain how the v and inverted v curves can be obtained in synchronous motor. Inverted v curves the variation of power factor against field current for constant power input.
Connect stator of motor to 3 phase supply as shown in the above figure through watt meters and ammeter. You may do so in any reasonable manner, but not in any way that. View lab report exp1 performance of a threephase synchronous motor. There is no such difference between iv curve and jv measurements. A synchronous does not possess starting torque but once brought near to machine synchronous speed, it is capable of developing torque. Explain the constructional details of alternator in.
Since the shape of these curves is similar to the letter v, thus they are called v curve of synchronous motor. 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. Determination of x d and x q of a salient pole synchronous machine from slip test. In this experiment two watt meter method is used to measure input power of motor. The arms of the v are under and overexcited regimes which generate reactive power output. Other motor technologies induction, dc, servo and step motors either need gear reducers, or electronic drives to match the speed of superior electric synchronous motors. The synchronous motor v curves shown above illustrate the effect of excitation field amps on the armature stator amps and on system power factor. Explain the constructional details of alternator in detail with neat sketches. Regulation of alternator using synchronous impedance method 2527 8. In other words, the function of this magnetizing current or lagging va drawn by the electromagnetic device is to set up the. 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. For drawing v curves and inverted v curves of synchronous motor following measuring instruments and accessories. A synchronous condenser or a synchronous compensator is a synchronous motor running without a mechanical load. Electromagnetic devices draw a magnetizing current from the a.
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. Ammeter reads the line current which is same as armature stator current. A synchronous motor is a doubleexcited machine, its armature. The synchronous motor operates at a precise synchronous speed, and hence is a constantspeed motor. Synchronous motor, like induction motor ie asynchronous motors, is a common ac motor. A short course on synchronous machines and synchronous. V and inverted v curves of synchronous motor free download as word doc. At what load angle is power developed in a synchronous motor becomes its maximum value. 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. 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.
This magnetizing current lags the applied voltage by almost 900. This file is licensed under the creative commons attribution 1. It is a kind of component that combines rotation and static, electromagnetic change and mechanical motion t. 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. Synchronous motors it is known, that the direct current generator operates satisfactorily as a motor. Synchronous condensor synchronous condensor is also known as synchronous compensator or synchronous phase modifier. Synchronous machines can also be used as motors, but they are usually built in very large sizes.
One well known approach is the utilization of synchronous motors sm. Adjust the field excitation of the synchronous machine so that about rated voltage 400v, ll is obtained. If graph of armature current drawn by synchronous motor is against field current is plotted then the resulted graph is known as a. 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. Why doesnt the v curve of a synchronous motor touch the. V curves and inverted v curves of synchronous motor. Bh curve experiment manual pdf laboratory manual v and inverted v curves of a 3phase synchronous motor. V and inverted v curves of a 3phase synchronous motor. Title of the paper 18pt times new roman, bold semantic scholar. V curve and inverted v curve for synchronous generator alternator also v curve of alternator. The vcurve is used to describe the power output of a synchronous machine with regard to the excitation current. What is the difference between iv curve and jv curve.
The curves are related to the phasor diagram in fig. To determine positive sequence, negative sequence and zero sequence reactances of an alternator. Synchronous motor is the heart of the power system. The cost of just the gear reduction or the cost of the electronic drive will usually exceed the total cost of. V curve and inverted v curve for synchronous generator. Hence, a synchronous motor has no self starting torque i. To start induction motor by rotor resistance starter 8. 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.
This magnetizing current lags by almost 90 o to the supply voltage. The two wattmeter method is used to measure input power of motor. Synchronous motors controlled by variablespeed drives are. Unlike the induction motor, whose operation always involves a lagging power factor, the synchronous motor possesses a variablepowerfactor. What is the difference between synchronous motor and. The ammeter is reading line current which is same as armature stator current. Equivalent circuit of single phase induction motor. We will now discuss what happens when motor is either overexcited or underexicted although we have already touched this point in art.
Eb is equal in magnitude to applied voltage v is known as 100% excitation. Exp1 performance of a threephase synchronous motor. Armature current is obtained by dividing this vector. Noload and block rotor tests on squirrel cage induction motor. The bottom tip of the v is pure active power output from the machine. Electrical machinesii lab manual pdf emii lab manual pdf. Sms with a 4pole rotor operated at 50hz rotate in synchronism with the supply at exactly 1500rpm. The corre sponding induction motor im however, has slip losses and rotates only at 1475rpm for a chosen 30 kw example. The input power to a threephase synchronous motor is given by p 3 v i cos. Synchronous and asynchronous electricmotors the electric motor is an electromechanical continuous energy conversion equipment that converts electrical energy into electrical energy mechanical energy.
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