Hence when the machine operates as a synchronous motor the emf phasor always lags the terminal voltage phasor by the load1torque angle. It is seen that vector difference of eb and v is zero and so is the armature current. A pm synchronous motor is driven by sine wave voltage coupled with the given rotor position. Energising c2 at the same time as deenergising o will cause the rotor of the synchronous motor to reach. The curve for power factor looks like inverted v curve. You may do so in any reasonable manner, but not in. The input power to a threephase synchronous motor is given by p 3 v i cos. Power factor correction with synchronous condenser for. For a given level of real power transmission, the position on the vcurve is controlled by the magnitude of the field current. 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. Search wegsynchronousmotors50019091brochureenglish. When a synchronous motor is loaded such as compressors, pumps, shears etc, as the load increases, its rotor falls back by a coupling angle. The motor vcurves describe the relationships among field current, armature current, load and power factor. In case when the machine has a single conductive contour, this model is described by.
The synchronous motor operates at a precise synchronous speed, and hence is a constantspeed motor. 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 other words, the function of this magnetizing current or lagging va drawn by the electromagnetic device is to set up the. 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.
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. The model demonstrate vector control of permanent magnet synchronous motor. The stator is the outer shell of the motor, which carries the armature winding. The vcurve is used to describe the power output of a synchronous machine with regard to the excitation current. Permanent magnet synchronous motor pmsm has better dynamic performance, smaller size and higher efficiency. The graph plotted between the armature current ia and field current if at no load the curve is obtained known as v curve. Such curves are called vcurves 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. Adjust the field excitation of the synchronous machine so that about rated voltage 400v, ll is obtained. Motor synchronous speed versus efficiency gain premium versus standard. Over exciting means giving more current to its field windingwinding which produces. 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. V and inverted v curves of synchronous motor free download as word doc. V and inverted v curves of synchronous motor lab manual scoop. A threephasesynchronous motor with a one permanent magnet pair pole rotor 3 synchronous motor operation synchronous motor construction. For the love of physics walter lewin may 16, 2011 duration. Pony motor u2 synchronous motor the correct operation of the above power circuit is as follows. In fact, at very low power levels the synchronous motor can be. Synchronous motor, like induction motor ie asynchronous motors, is a common ac motor. Hunting or surging or phase swinging of a synchronous motor is caused by either 1. Synchronous motor can also be used for powerfactor correction in an industrial plant consisting of a large number of induction motors. 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. Synchronous motor which is over excited is referred to as a synchronous condenser. Closing q and energising m, ci and c 3 causes pony motor to drive synchronous motor up to near synchronous speed.
We will now discuss what happens when motor is either overexcited or underexicted although we have already touched this point in art. Stopping the synchronous motor example a 1500 kw, 4600 v, 600 rpm motor is stopped by using the shortcircuit method e0 2400, xs 16. To repeat the above, with synchronous motor loaded to half the full load and 34 the full load. 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. Unlike the induction motor, whose operation always involves a lagging power factor, the synchronous motor possesses a variablepowerfactor. This file is licensed under the creative commons attributionshare alike 3. When w and wm are converted into cycles per second or hz and revolutions per minute respectively, we have. 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. Synchronous motor is the heart of the power system. Effect of excitation on armature current and power factor. Synchronous motors the cooling systems most commonly used are. Skubov and khodzhaev in nonlinear electromechanics. 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.
You should also make a dc measurement of stator winding linetoline resistance using a dmm. Model uses model of pmsm in rotor frame of reference. Why doesnt the v curve of a synchronous motor touch the. V curves and inverted v curves of synchronous motor. Armature current is obtained by dividing this vector. 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. Sensorless field oriented control of 3phasepermanent.
Vector control of permanent magnet synchronous motor. This winding is spatially distributed for polyphase ac current. At what load angle is power developed in a synchronous motor becomes its maximum value. V and inverted v curves of synchronous motor electrical. 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. Vector diagram correlation of leading and lagging power. The bottom tip of the v is pure active power output from the machine. Generally the construction of the synchronous motor is electrically more efficient than a nonsynchronous motor. Synchronous machines can also be used as motors, but they are usually built in very large sizes. Noload and block rotor tests on squirrel cage induction. This armature creates a rotating magnetic field inside the motor. V curve and inverted v curve for synchronous generator alternator also v curve of alternator.
V and inverted v curves of a 3phase synchronous motor. What links here related changes upload file special pages permanent link. The curves are related to the phasor diagram in fig. Record all nameplate information for the induction motor.
Vector control of pm synchronous motor drive system using. There is a speed control loop to regulate the speed. Permanent magnets are rigidly fixed to the rotating axis to create a constant rotor flux. 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. The vcurve analysis and study of synchronous motors using. 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. What is the difference between synchronous motor and. Eb is equal in magnitude to applied voltage v is known as 100% excitation.
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. A novel calculation method on the current information of. A synchronous motor is composed of the following parts. It is a kind of component that combines rotation and static, electromagnetic change and mechanical motion t. This magnetizing current lags by almost 90 o to the supply voltage. The arms of the v are under and overexcited regimes which generate reactive power output. In the synchronous motor, the basic magnetic field is obtained by direct current excitation rather than. To determine positive sequence, negative sequence and zero sequence reactances of an alternator.
Power factor correction using synchronous motors all. Bifurcation curves for synchronous electrical machine. For drawing v curves and inverted v curves of synchronous motor following measuring instruments. How many amperes of incandescent lighting may be added to the plant at the same kva load if the. 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. 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. In recent years, with the rapid development of electric power electronics technical, rare earth permanent magnetic materials and the increasingly sophisticated. The scim squirrel cage induction motor power factor is 0. A short course on synchronous machines and synchronous. A 400hp scim and a 400hp synchronous motor both operating at 90% efficiency. Index terms interior permanent magnet synchronous motor, current information for vector inverter, electric vehicle, field. 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. One of the wellknown and the simplest mathematical models of electrical synchronous machine is a pendulum with magnetoelectrical extinguishers stoker in nonlinear vibrations. V curve of a synchronous motor v curve is a plot of the stator current versus field current for different constant loads.