Investigation on generator loss of excitation protection in. Pdf compatibility design of non salient pole synchronous. Determination of load angle for salientpole synchronous. The salient pole rotor shown in figure 34, view b, is used in lowspeed alternators. Cylindrical rotor alternators are usually long, and the problem of air f low requires very special attention. Phasor diagram of salient pole synchronous machine for generator and motor mode duration. Salient pole synchronous motor power developed by a salient pole synchronous motor effects of excitation on armature current and power factor constantpower lines construction of vcurves hunting or surging or phase swinging methods of starting procedure for starting a synchronous motor comparison between. Study of salient poles synchronous generator by finite elements analysis. In any generator set installation, the frame of the generator must be positively connected to an earth ground or to the hull of the vessel.
The first method uses optical encoder to detect the rotor position. Ger4212 ge generator rotor design, operational issues, and. Designed, built and tested in the motor factory, solid salient pole rotors are suitable for applications requiring long duty cycles. Synchronous generator rotor construction round rotor salient pole two pole w s 3600 rpm four pole ws 1800 rpm eight pole ws 900 rpm fig. We are quite familiar with synchronous generator or often called alternator. This paper is focused design calculation of 30 mva, 11 kv, 50 hz, two pole non salient poles synchronous generator that use in gas turbine power plant. The goal of this analysis is to determine the machine parameters in steadystate regime and in. This type of rotor consists of large number of projected poles called salient poles, bolted on a magnetic wheel. Construction of ac generator of salient pole type rotor is shown in the figure above. Ee 340 spring 2011 university of nevada, las vegas. Salient pole type rotor is used in low and medium speed alternators. The generator load current produces a rotating magnetic field in the stator armature which tries. Salient pole synchronous generator power angle curve.
The synchronous electrical generator also called alternator belongs to the family of electric rotating machines. The two main types of synchronous machine are cylindrical rotor and salient pole. This is the working principle of synchronous generator or alternator. Construction of synchronous machines the rotor of a synchronous machine is a large electromagnet. The machine used for this experiment is somewhat salient, but the impact of. Therefore from the literal meaning of saliency one can guess that salient. It is made of cast iron to provide an easy path for the magnetic flux. If you could compare the physical size of the two types of rotors with the same electrical.
So if we plot the magnitudes of the induced emf against the time, we get an alternating nature of the induced emf shown figure above. The salient pole rotor often consists of several separately wound pole pieces, bolted to the frame of the rotor. The pictures below show the stator and rotor of a hydroelectric generator and the rotor of a turbine generator. Construction of a salient pole rotor is as shown in the figure at left. Base values, transformation ratio, and rotor parameters referred to the stator. Difference between cylindrical and salient pole rotor. It is keyed to the shaft and at the outer surface, pole core and pole shoe are keyed to it. Synchronous generator rotor fields may be either salient or non salient pole. The phrase salent pole is used to specify a specific internal field winding configuration around the magnet of a generator. Function of a generator rotor this section covers the generator fields function in two main areas. Apr 25, 2018 we are quite familiar with synchronous generator or often called alternator. The red arrows indicate the direction of the flux produced by the field windings.
Dec 18, 2018 the former is mostly used in thermal power plants and nuclear power plants. Model the dynamics of threephase roundrotor or salient pole synchronous machine. Rotors are made laminated to reduce eddy current losses. The projected poles are made up from laminations of steel. Cylindrical rotor alternators are usually long, and the problem of air f low. Mediumspeed synchronous generators mediumspeed synchronous generators product overview product overview our new mediumspeed threephase highvoltage generators in salient pole design are available at 900 mm to 1,120 mm shaft height with eight to twelve poles. If the machine is being used as a generator, torque is being supplied by a primemover. This modification is made to cope with the very high power of the order of few 100 megawatts produced in an ac generator contrary to that of a dc generator. Other members of the family are the directcurrent dc motor or generator, the induction motor or generator, and a number of derivatives of all these three. The phasor diagram of a salient pole synchronous generator. The salient pole rotor has the following important parts. Ger4212 ge generator rotor design, operational issues. What is synchronous generator asynchronous generator. The theory proposes to resolve the given armature mmfs into two mutually perpendicular components, with one located along the axis of the rotor of the salient pole.
Mar 04, 2020 there are mainly two types of rotors used in construction of alternator. In most practical construction of alternator, it is installed with a stationary armature winding and a rotating field unlike in the case of dc generator where the arrangement is exactly opposite. Pdf study of salient poles synchronous generator by. What is the difference between a salient pole and a. A field coil is an electromagnet used to generate a magnetic field in an electromagnetic machine, typically a rotating electrical machine such as a motor or generator. Model the dynamics of threephase roundrotor or salientpole. The analysis of salient pole synchronous motor is based on the blondels two reaction. It consists of a coil of wire through which a current flows. In salient pole type of rotor consist of large number of projected poles salient poles mounted on a magnetic wheel. When the field is rotated by a prime mover, voltages are induced in the stator coils because they are cutting the flux of the. Basics of electricity generator theory pjm2014 8620.
In structure, highspeed synchronous generator uses hidden pole rotor, and low medium speed synchronous generator uses salient pole rotor. In a rotating machine, the field coils are wound on an iron magnetic core which guides the magnetic field lines. The direct and quadrature axis components of current and reactance are. The salient pole generator explores the principles and characteristics of salient pole generators.
Salient pole also called spider or projected pole means the rotor has distinct pole windings mounted on the rotor shaft using dovetail joints as seen in figure 1. In fact, a given synchronous machine may be used, at least theoretically, as an alternator, when driven. The salientpole rotor often consists of several separately wound pole pieces, bolted to the frame of the rotor. The armature with a threephase winding is on the stator where voltage is induced. Most synchronous generators that have brushless exciters also use slip rings and brushes as an auxiliary source of field dc current in emergencies. This paper presents the finite elements analysis fea of a salient poles synchronous generator. Due to the salient pole construction of the rotor and the asymmetry of the starting winding, the distribution of the magnetic flux density in the air gap differs from the sinusoidal, and the electromagnetic torque in the asynchronous mode has a constant component and a variable one that fluctuates with a double frequency. The choices of specific loadings are magnetic loading and electric loading are involved in that. This paper presents two methods for load angle determination for salientpole synchronous generator. As the field continues to turn and the north pole starts to move away from the winding, the current decreases as the strength of the field cutting the winding decreases. Salient pole synchronous motor power developed by a salient pole synchronous motor effects of excitation on armature current and power. Construction of synchronous machines in a synchronous generator, a dc current is applied to the rotor winding producing a rotor. Pole of the field moves past the winding, a large current flows through the winding. There are some disturbing factors in salient pole alternators which are analysed below.
Introduction a salient pole synchronous motor is an a. The power output of a synchronous generator is the sum of the power due to the directaxis current d and the power due to the quadratureaxis current. Normally salient pole machines can carry 15%25% 2 rated load without loss of synchronism after loe. A phasor diagram shows the relationship between voltages and currents. Salient pole article about salient pole by the free. The poles are supplied by direct current or magnetized by permanent magnets. Dynamic modelling and simulation of salient pole synchronous. This paper presents two methods for load angle determination for salient pole synchronous generator. Construction of a synchronous machine circuit globe. The theory which gives the method of analysis of the disturbing effects caused by salient pole construction is called two reaction theory. The terminal voltage, v t, is taken as the reference phasor.
Model the dynamics of threephase roundrotor or salient. The salientpole rotor shown in figure 34, view b, is used in lowspeed alternators. Solid salient pole motor synchronousmotor ge power. Two reaction theory salient pole synchronous machine two reaction theory was proposed by andre blondel. A salient pole synchronous generator, as shown in fig. It contains everything needed for salient pole generator experiments including resistive, capacitive and inductive load banks. The rotor is a large magnet with poles constructed of steel lamination projecting out of the rotors core. Main generator components an ac synchronous generator is significantly more complex than. Blondel two reaction theory salient pole alternators theory.
But for cylindrical pole generator, the generator will lose synchronism after loe even carrying very small active load, in other words, it is not allowed to operate at leading power factor. When neither pole is nearest the winding, the current through the winding is zer o. The final expression for the phase voltage of a salient pole synchronous generator is as mentioned in eq. The salient pole type of rotor is generally used for slow speed machines having large diameters and relatively small axial lengths. In english, salient means sticking out or most noticeable or. The rotor winding is provided on these poles and it is supported by pole shoes. In this phasor diagram, the armature current needs to be resolved into two components one in parallel with e a. Investigation on generator loss of excitation protection. The direct and quadrature axis components of current and reactance are same as defined earlier for the synchronous generators.
The slow speed salient pole alternators are ventilated by the fan action of the salient poles which provide circulating air. This cycle continues as conductor rotates at a certain speed. The rotor winding is provided on these poles and it. Describe the process of electromagnetic induction identify the major components of an ac generator apply the formula for rotational speed describe generator governor control. The cooling medium, air or hydrogen is cooled by passing over pipes. Salient pole synchronous motor electrical engineering. The salientpole synchronous generator thus has a directaxis reactance and a quadratureaxis reactance, which must be accounted for when analyzing a salientpole synchronous generator. Synchronous generator rotor fields may be either salient or nonsalient pole. The first term is the same as for a round rotor machine with x s x d and constitutes the major part in power transfer. It is known as the direct axis or d axis component.
The simplest generator consists of a loop of wire rotating between two permanent magnet poles. Synchronous generator working principle electrical academia. It has a large number of projecting salient poles, having their cores bolted or dovetailed onto a heavy magnetic wheel of castiron, or steel of good magnetic quality fig. There are mainly two types of synchronous generator from rotor construction point of view.
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