Alternator generator mcqs with explanatory answers. Now, with this background, let us discuss principle first. The dc power required for excitationapproximately one to a. The synchronous electrical generator also called alternator belongs to the family of.
Construction of a salient pole rotor is as shown in the figure at left. Because a salient pole rotor turns at low speed 50 to 300 r. Synchronous machines notes part2 electric equipment. Alternator generator mcqs with explanatory answers 1. Mechanical degrees x number of pole pairs in a fourpole generator two pole pairs, each pole pair moves 360 mechanical degrees, so the total electrical degrees moved is.
The open and flexible design is ideal for lecturers to create their own experiments, as well as student project work. Ventilation or cooling of an alternator the slow speed salient pole alternators are ventilated by the fan action of the salient poles which provide circulating air. 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. The synchronous generator is connected to a threephase power grid emulator. A vector drive controls the speed of the prime mover and allows investigations into load. Difference between salient pole and nonsalient pole rotors or salient pole alternator and cylindrical alternators used in synchronous generator.
The construction of salient pole rotor cannot withstand high mechanical stress. Differentiate between transient and subtransient reactance btl 4 analyze 5. Construction of alternator synchronous generator types. The projected poles are made up from laminations of steel. Consequently the methods for finding out the regulation of cylindrical rotor machines when applied to salient pole machines give results which are not correct.
The theory which gives the method of analysis of the disturbing effects caused by salient pole construction is called two reaction theory. Dec 18, 2018 a generator is a device that converts mechanical energy into electrical energy. Regulation of alternator at full load is found to be. Compare salient pole alternator and cylindrical pole. Describe with neat sketches the constructional details of a salient pole type alternator. In salient pole type of rotor consist of large number of projected poles salient poles mounted on a magnetic wheel. Mar 06, 2019 alternator synchronous generator and types of alternators march 6, 2019 february 24, 2012 by electrical4u an alternator is defined as a machine which converts mechanical energy to electrical energy in the form of alternating current at a specific voltage and frequency. Salient pole rotors are most commonly used in slow speed applications and tend to be at least six poles.
This paper presents two methods for load angle determination for salient pole synchronous generator. The slow speed salient pole alternators are ventilated by the fan action of the salient. Two reaction theory salient pole synchronous machine. Synchronizing method, effect of wrong synchronizing, load sharing between alternators in parallel. Development of salient pole rotor for conventional automotive and aircraft alternator to increase reliability the following faculty members have examined the final copy of this thesis for form and content, and recommend that it. The phrase salent pole is used to specify a specific internal. Cylindrical rotor alternators are usually long, and the problem of air f low requires very special attention. The phasor diagram of a salientpole synchronous generator. The magnetic poles can be either salient sticking out of rotor surface or non salient construction. Short circuit ratio of a synchronous machine the short circuit ratio scr of a synchronous machine is defined as the ratio of the field current required to generate rated voltage on an open circuit to the field current required to circulate rated armature current on short circuit. Development of salient pole rotor for conventional automotive and aircraft alternator to increase reliability the following faculty members have examined the final copy of this thesis for form and content, and recommend that it be accepted in partial fulfillment of the requirement for. Development of salient pole rotor for conventional.
Two reaction theory of salient pole synchronous alternator. Blondel two reaction theory salient pole alternators theory. The cooling medium, air or hydrogen is cooled by passing over pipes through which cooling water is circulated and ventilation of the alternator. The proposed smpi voltage regulator has been evaluated experimentally by using a laboratory setup whose structure was presented in fig. To find xd and xq of a salient pole rotor type synchronous. Power equation derivation of a salient pole synchronous machine. The salient pole type of rotor is generally used for slow speed machines. A leading pf load on an alternator implies that its voltage regulation shall be a.
What is synchronous generator asynchronous generator. According to the structure, it can be divided into two types. Btl 3 apply ee8401 question bank electrical machines 2 4. No load and blocked rotor test on 3phase induction motor. The speed of an alternator is given as n 120fp hence the speed of an alternator is inversely proportional to the number of poles. Voltage regulation of an alternator by emf and mmf methods. Nonsalient or cylindrical pole type salient pole type. Salient pole synchronous generator power angle curve. The axis along the axis of the rotor is called the direct or the d axis. Hence the armature flux and field flux cannot vary sinusoidally in the air gap. Perreault vahe caliskan massachusetts institute of technology abstract this paper introduces a new design for alternator systems that provides dramatic increases in peak and average power output from a conventional lundell alternator, along with substantial improvements in efficiency. Determination of load angle for salientpole synchronous. Ee8401 question bank electrical machines 2 regulation 2017 anna university free download. Ee8401 question bank electrical machines 2 regulation 2017.
On the theory of salient pole alternators with electromagnet. Regulations on 3phase salient pole alternator by slip test. It contains everything needed for salient pole generator experiments including resistive, capacitive and inductive load banks. The salient poles are mounted on large circular steel frame which is fixed to the shaft of the alternator. The red arrows indicate the direction of the flux produced by the field windings. Salient pole type rotors are designed for alternators with many number of poles and cylindrical rotors are designed for alternators with. Understanding the alternator four wires connect the alternator to the rest of the charging system. Due to this, the mmfs of armature and field act upon the same magnetic circuit all the time hence can be added vectorially.
In this type, salient or projecting poles are mounted on a large circular steel frame which is fixed to the shaft of the alternator as shown in fig. Two reaction theory salient pole synchronous machine two reaction theory was proposed by andre blondel. The short circuit ratio can be calculated from the open circuit characteristic o. The first method uses optical encoder to detect the rotor position. To find xd and xq of a salient pole rotor type synchronous machine by slip test apparatus. The salient pole generator explores the principles and characteristics of salient pole generators. Blondels two reaction theory, phasor diagram, direct axis and quadrature axis synchronous reactances, power angle characteristics, slip test. Determination of load angle for salientpole synchronous machine. S is used by the regulator to monitor charging voltage at the battery. In this paper, various performance equations are derived from phasor diagrams of a three phase non salient pole cylindrical rotor synchronous generator of known armature resistance and of. The rotor of a synchronous machine is a large electromagnet. Explain the constructional details of alternator in.
The pole structure of the rotor of a salient pole machine makes the air gap highly nonuniform. There are some disturbing factors in salient pole alternators which are analysed below. Be semestervith electrical question bank electrical. D7escribe a method of determining direct and quadrature axis reactance of salient pole alternator. Distinguish between the use of salient pole and round rotor synchronous machines. Dec 07, 2019 because a salient pole rotor turns at low speed 50 to 300 r. Demonstrate why is the field system of an alternator made as a rotor. Consider a 2 pole, salient pole rotor rotating in the anticlockwise direction within a 2 pole stator as shown in the figure below. What are the two classification synchronous machines.
The rotor winding is provided on these poles and it. Alternator synchronous generator and types of alternators. To pre determine the regulation of an alternator at full load at different power factors. Salientpole machines have an additional winding in the rotating mem ber. Ee8401 question paper electrical machines 2 regulation 2017. When the generator is in overrun mode, resistors dissipate the reverse power. The objective of this unit is to deal with the rigorious details of most useful methods to find the regulation of cylindrical and salient pole alternators with phasor diagrams. Ee 340 spring 2011 university of nevada, las vegas. Thus a salient pole rotor consists of poles projecting out. Voltage regulation of an alternator is defined as the change in terminal. There are mainly two types of rotors used in construction of alternator. The number of cycles of emf in one revolution would be a 24. Regulation of 3phase alternator by zpf and asa methods.
It is done only on salient pole alternatorsnon uniform field. A new design for automotive alternators semantic scholar. The rotor of the salient pole alternator has 24 poles. It is a test done in alternator to measure the value of direct axis synchronous reactancexd and quadrature axis synchronous reactancexq. B is the alternator output wire that supplies current to the battery.
The salient pole rotor has following disadvantages. Alternators are also known as synchronous generators. In this paper, various performance equations are derived from phasor diagrams of a three phase nonsalient pole cylindrical rotor synchronous generator of known armature resistance and of. 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. Blondels two reaction theory, phasor diagram, direct axis and quadrature axis synchronous reactances, power angle characteristics, slip.
Describe the process of electromagnetic induction identify the major components of an ac generator apply the formula for rotational speed describe generator governor control. Ig is the ignition input that turns on the alternatorregulator assembly. This type of construction is commonly employed in machines coupled to hydroelectric turbines which are inherently slowspeed ones so that the salient pole synchronous generator has multiple pole pairs as different from machines coupled to highspeed steam turbines 3,0001,500 rpm which have a two or four pole structure. A graphical method has been developed for rapidly determining from two reactances the regulation of alternators for a wide range of power factor. Draw a neat sketch showing the various parts of a synchronous machine. Synchronous generator, that is, an alternator ac generator with the same rotor speed as the rotating magnetic field of the stator. A slidingmode voltage regulator for salient pole synchronous. Mar 28, 2015 regulation graph for salient pole motor. 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. A reduced windage loss, b reduced bearing loads and noise, c reduced noise, d adaptability of low and medium speed operation, e, leave your comments or download question paper. Mar 25, 2018 power equation derivation of a salient pole synchronous machine.
Derivation of various power conditions in alternators and. Alternator on load synchronous reactance vector diagrams of loaded alternator voltage regulation rotherts m. Sm28 two reaction theory of salient pole alternator. Performance of synchronous generator connected to infinite bus, under constant power. The rotor winding is provided on these poles and it is supported by pole shoes. Why a 3phase synchronous motor will always run at synchronous speed.
Regulation of 3phase alternator by emf and mmf methods. Basics of electricity generator theory pjm2014 8620. Salient pole machines have more diameter and less axial length. The magnetic poles can be either salient sticking out of rotor surface or nonsalient construction. An alternator is defined as a machine which converts mechanical energy to electrical energy in the form of alternating current at a specific voltage and frequency. 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. Rotors are made laminated to reduce eddy current losses. Pdf analysis of nonsalient pole synchronous generator. Manual or automatic voltage regulation avr excitation controls the output voltage of the generator. The voltage regulation of an alternator is defined as the change in terminal.
But in salient pole type alternators, the length of the air gap varies and the reluctance also varies. This paper presents two methods for load angle determination for salientpole synchronous generator. In a synchronous generator, a dc current is applied to the. In english, salient means sticking out or most noticeable or. As the speed of the alternator is low, numbers of poles must be higher resulting diameter of the rotor must be large and short axial length. In case of salient pole machines regulation is found out by applying blondels two reaction theory. Electrical machines 2 question bank ee8401 pdf free download. Power equation derivation of a salient pole rotor synchronous.
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