Adjust the field excitation of the synchronous machine so that about rated voltage 400v, ll is obtained. A pm synchronous motor is driven by sine wave voltage coupled with the given rotor position. Highperformance variablespeed motor drives are often constructed using a permanentmagnet synchronous motor. Motor that run at constant speed at all load applied to it. Such curves are called vcurves of synchronous motor. 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 machines have parabolic type characteristics. Permanent magnet synchronous motor driver and control. 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.
V curves and inverted v curves of synchronous motor. The input power to a threephase synchronous motor is given by p 3 v i cos. About this video what is vcurve in synchronous motor what is inverted vcurve in synchronous motor full explanation about under excitation. 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. In general, over excitation will cause the synchronous motor to operate at a leading power factor, while under exercitation will cause the motor to operate at a lagging power factor. The cost of just the gear reduction or the cost of the electronic drive will usually exceed the total cost of. The curves are related to the phasor diagram in fig. 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. Tricky synchronous motors multiple choice questions and answers pdf 101. But initial lagging current becomes unity and then becomes leading. The arms of the v are under and overexcited regimes which generate reactive power output. The vcurve analysis and study of synchronous motors.
Such curves are called v curves of synchronous motor. On standard induction motors, the fullload speed is typically 96% to. If excitation is varied from very low under excitation to very high over excitation value, then current ia decreases, becomes minimum at unity p. V and inverted v curves of synchronous motor electrical. The bottom tip of the v is pure active power output from the machine. Vector diagram correlation of leading and lagging power. When two unlike poles are brought near each other, if the magnets are strong, there exists a tremendous force of. Stardelta starting of a three phase induction motor 10.
Hence when the machine operates as a synchronous motor the emf phasor always lags the terminal voltage phasor by the load1torque angle. A similar phenomenon is observed in case of the nsc. 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. Power factor correction with synchronous condenser for. V curve of a synchronous motor v curve is a plot of the stator current versus field current for different constant loads. The motor vcurves describe the relationships among field current, armature current, load and power factor. Regulation of 3phase alternator by zpf and asa methods 9. Understanding motor nameplate information nema vs iec. This magnetizing current lags the applied voltage by almost 900. 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. A short course on synchronous machines and synchronous.
This file is licensed under the creative commons attribution 1. Wegtheabcsofsynchronousmotorsusaem200syn42brochureenglish. You may do so in any reasonable manner, but not in any way that. V and inverted v curve of three phase synchronous motor page link. This winding is spatially distributed for polyphase ac current. Pdf startup of largepower synchronous motor with the 6 kv. If graph of armature current drawn by synchronous motor is against field current is plotted then the resulted graph is known as a. Difference between synchronous and asynchronous motor. Synchronous motor vcurves geogebra dynamic worksheet. Vector control of pm synchronous motor drive system using. 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. Control parameters and motor measurements that are presented in this report is nat urally related to the type of motor and load. Electromagnetic devices draw a magnetizing current from the a.
When its load angle is equal to the impedance angle. An induction motors speed is always less than synchronous speed and it drops off as load increases. The generated stator flux together with the rotor flux, which is generated by a rotor magnet, defines the torque, and thus speeds, of the motor. V curve and inverted v curve for synchronous generator alternator also v curve of alternator. The steadystate characteristics of a synchronous motor represented by phasor diagrams are shown as function of the excitation voltage e. 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. Vector control of pm synchronous motor drive system using hysteresis current controller 1rajesh p. 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. By controlling dclink voltage of the nsc reactive power transfer can be controlled. A synchronous motor is composed of the following parts. Tricky synchronous motors multiple choice questions and. The stator is the outer shell of the motor, which carries the armature winding. 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 motor is an electromechanical device which converts electrical energy to mechanical energy. Synchronous machines can also be used as motors, but they are usually built in very large sizes. Vcurves and inverted vcurves of synchronous motor youtube. Starting and pullin torques are designed to accommodate electrical system. Synchronous motor can also be used for powerfactor correction in an industrial plant consisting of a large number of induction motors. Record all nameplate information for the induction motor. From simulation results shown in table 3, v curve and inverted v curve is plotted in figure 17. Since the shape of these curves is similar to the letter v, thus they are called v curve of synchronous motor. V curve and inverted v curve for synchronous generator. You should also make a dc measurement of stator winding linetoline resistance using a dmm. Synchronous motors can operate at leading power factors, providing vars to the power system, reducing demand charges often caused by induction motors.
In synchronous motors performance characteristics obtained by v curves and inverted vcurves. When w and wm are converted into cycles per second or hz and revolutions per minute respectively, we have. Applications society annual meeting, las vegas, nv, 2012. Rgpv syllabus for 5th sem ex branch get best books pdf.
A synchronous machine is an ac machine whose speed under steadystate. For example, for 1800 rpm synchronous speed, an induction motor might have a fullload speed of 1748 rpm. A reduced switch acac converter with the application of d. 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. Constant speed synchronous motor speed is unaffected by line or load conditions, providing greater operating flexibility. Unlike the induction motor, whose operation always involves a lagging power factor, the synchronous motor possesses a variablepowerfactor. At what load angle is power developed in a synchronous motor becomes its maximum value. For a given level of real power transmission, the position on the vcurve is controlled by the magnitude of the field current. The vcurve is used to describe the power output of a synchronous machine with regard to the excitation current. Synchronous motor working principle instrumentation tools. The v curve and inverted v curve is obtained by varying field excitation of the synchronous motor. What are v and inverted v curves of synchronous motor.
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. V and inverted v curve of three phase synchronous motor posted by. A synchronous motor is a doubleexcited machine, its armature. The graph plotted between the armature current ia and field current if at no load the curve is obtained known as v curve. Why doesnt the v curve of a synchronous motor touch the. It is seen that vector difference of eb and v is zero and so is the armature current. This armature creates a rotating magnetic field inside the motor. The synchronous motor operates at a precise synchronous speed, and hence is a constantspeed motor.
Synchronous motor which is over excited is referred to as a synchronous condenser. Synchronous motor mainly runs on principle of magnetic locking between rotor and rmfrotating magnetic field. To start induction motor by rotor resistance starter 8. Vcurve is an important running curve of salientpole synchronous electric machine for it implies how to adjust reactive power when the machine is connected to an electric power grid. 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. Generally the construction of the synchronous motor is electrically more efficient than a nonsynchronous motor. Over exciting means giving more current to its field windingwinding which produces. In fact, at very low power levels the synchronous motor can be. Synchronous motor, to supply complete application data. Unit v synchronous machineiii synchronous motor operation, starting and stopping of synchronous motor, pull in torque, motor under load power and torque, reluctance torque, effect of excitation, effect of armature reaction, power factor adjustment, v curves, inverted v curves, synchronous motors as power factor correcting device, super. The motor is mounted in a test rig that allows one to control the torque applied to the motor shaft and to measure both rpm and torque.