What is meant by synchronous impedance of an alternator. The synchronous impedance method is based on the concept of replacing. The main advantages of this method is the value of synchronous impedance z s for any load condition can be calculated. Regulation of alternator voltage electrical impedance scribd. Voltage regulation of alternator emf and mmf methods duration. In real synchronous machines of any size, the armature resistance r a synchronous machines a s we have seen in section 4. When the alternator is loaded the terminal voltage decreases as the drops in the machine stars increasing and hence it wil. In the open circuit test for determining the synchronous impedance, the alternator is. There are 3 methods for determining voltage regulation of an alternator i. Oct 22, 2017 a no load voltage is induced in the stator coils of alternator when rotor is rotated by a prime mover. To calculate voltage regulation of synchronous machine by m. Mmf method is used for determining the voltage regulation of an alternator or synchronous generator is also called ampere turns method or rotherts mmf method.
Voltage regulation of alternator and solved example youtube. Apr 20, 2016 normally for voltage regulation calculation, we use methods like. The magnitude of this change depends not only on the load but also on the load power factor the voltage regulation of an alternator is defined as the rise in voltage when fullload is removed field excitation and speed remaining the same divided by the rated terminal voltage. In this experiment, the emf and mmf methods are used. Iron and friction losses of the two machines are made equal by joining the series field. Why is the synchronous impedance method of estimating voltage regulation considered as pessimistic method. Objective questions on alternator page 2 electrical. Pdf principles of electrical machines book by vk mehta. Adams engineering college, paloncha eee department emii lab experiment no. Therefore also known as synchronous impedance method. The real and reactive output powers of the synchronous generator are p v i v i out t l a 3 cos 3 cos q vi viout t l a 3 sin 3 sin recall that the power factor angle is the angle between v and i a and not the angle between e a and i a. Methods to determine voltage regulation of alternator q1. Actual load need not be connected to the alternator and hence method can be used for very high capacity alternators.
To analyze performance of three phase induction motor. Which of the method more accurate for determine the. The three terminals of switch are short circuited by an ammeter. Mmf method of voltage regulation mmf method is also known as ampere turn method. To compensate impedance drop the regulating components. This zero power factor zpf method is used to determine the voltage regulation of synchronous generator or alternator. Once e ph is known, the regulation of an alternator can be predicted as.
When the power gradually increases, the current reduces passing through three characteristic periods. Jun 04, 2015 synchronous reactance from the above discussion, it is clear that for the same field excitation, terminal voltage is decreased from its noload value e0 to v for a lagging power factor. The open circuit voltage and short circuit current of a 3 phase, star connected alternator are 1050 v and 250 a respectively. Aug 28, 2018 derivation of various power conditions in alternators and synchronous motors august 28, 2018 february 24, 2012 by electrical4u in order to derive various conditions for power in both alternators and synchronous motors, let us consider the general problem of power flow through inductive impedance. Voltage regulation of alternator and its determination by synchronous impedance method. To find the regulation of a three phase alternator by emf method. Synchronous impedance with armature reaction values of r and x are usually not given for alternators. Nov 22, 2015 voltage regulation of alternator and solved example ee academy. Now joining the terminals a2, b2 and c2 of the 3 primary coils of the. Jun 11, 2015 voltage regulation of synchronous generator by mmf method. Objective type question of alternator or synchronous generator with explanation multiple choice question of alternator or synchronous generator. Voltage regulation of synchronous generator by mmf method.
Voltage regulation of alternator emf and mmf methods. Protection of synchronous generators involves the consideration of faults and harmful abnormal operating conditions, more so than the protection of other power system elements. Voltage regulation of a sy nchronous generator the voltage regulation of a sy nchronous generator is the rise in voltage at the terminals when the load is reduced from full load rated value to zero, speed and field current remaining constant. Hence regulation of the alternator at any load condition and load power factor can be determined.
Blondels two reaction theory, phasor diagram, direct axis and quadrature axis synchronous reactances, power angle characteristics, slip test. Synchronous machines notes part2 electric equipment. Solved regulation of alternator by synchronous impedance. The usual method of measuring synchronous impedance is by the short circuit test, which consists in running the alter nator at normal speed with its armature short circuited thru an ammeter. When a balanced load is connected across stator winding a balanced set of 3 phase currents flow with a phase relation with no load voltage depen. A no load voltage is induced in the stator coils of alternator when rotor is rotated by a prime mover. To observe the effect of excitation and speed on induced e. Armature reaction is different from armature leakage reactance. For calculating the regulation, the synchronous method requires the following data. To pre determine the regulation of an alternator at full load at different power factors using synchronous impedance and mmf methods. Zero power factor method of an alternator is used to find its a efficiency b voltage regulation c armature resistance d synchronous impedance. In case of small generators it can be determined by direct loading whereas in case of large generators it cannot determined by direct loading but will be usually predetermined by different methods. Following are the different methods used for predetermination of regulation of alternators.
Which of the method more accurate for determine the voltage. Compared to other methods, the value of voltage regulation obtained by the synchronous impedance method is always higher than the actual value and therefore this method is called the pessimistic method. Electrical machine alternators objective questions with answers electrical objective questions with answers. The synchronous impedance method is based on the concept of replacing the effect of armature reaction by an imaginary reactance the magnetomotive force mmf. The armature of alternator or synchronous generator is connected to tpst switch. Synchronization of two three phase alternators, by. The alternator or synchronous generator is coupled with the prime mover to drive alternator at synchronous speed. But while calculating voltage regulation of synchronous machine by zero power factor method or potier method we separate armature leakage reactance and armature reaction effects and calculate voltage regulation so we get almost correct value of voltage regulation by zero power factor method or potier method. Alternator if there are n ph turns per phase, then synchronous generator e ph 4. Methods of synchronizing of alternator all dark lamp method. There are various methods for determination of regulation one of them is synchronous impedance method is based on the concept of. The complex addition of resistance, r and synchronous reactance, jx s can be represented together by a single. Normally for voltage regulation calculation, we use methods like. The synchronous impedance is found from the oc test.
Voltage regulation of alternator using synchronous impedance. The synchronous impedance method of finding the voltage regulation by a cylindrical rotor alternator is generally considered as the test data obtained at the rated speed on a threephase yconnected synchronous generator are given as follows. The regulation of a synchronous generator alternator is the rise in voltage at the terminals when the load is reduced from full load rated value to zero, speed and field current remaining constant. Ppt alternator powerpoint presentation free to view id. Contents defination methods to determine voltage regulation 1 synchronous impedance method 2 mmf method 3 zero power factor method.
Basic search techniques, tree searching and general search trees, symbolic table. Or the numerical value of the regulation is defined as the percentage rise in voltage when full load at the specified powerfactor is switched off with speed. The voltage regulation of an alternator is defined as the change in its terminal voltage when the full load is removed, keeping field. To study and measure positive, negative and zero sequence impedance of a alternator 5. The open circuit characteristic is the graph of the circuit. Answer to what is meant by synchronous impedance of an alternator. To study and measure direct and quadrature axis reactance of a 3 phase alternator by slip test 4. Voltage regulation of alternator by mmfampere turn method. Synchronous alternator protection principles and systems ee. Alternators ii electrical impedance inductance scribd. In the operation of an alternator, the armature resistance drop ir a and armature leakage reactance drop ix l are actually emf quantities while the armature reaction is basically mmf quantity.
Voltage regulation of alternator by emf method and solved. How is the regulation of alternator predetermined by slip test. A convenient way to compare the voltage behaviour of two generators is by their voltage regulation vr. Laboratory manual electrical machines and applications. Zero power factorzpf or potier triangle method for. It is clear that with change in load, there is a change in terminal voltage of an alternator. For calculating the regulation, the synchronous method requires the following. Regulation of 3phase alternator by zpf and asa methods 9.
What is the difference between salient pole alternator and cylindrical rotor type alternator. Voltage regulation of an alternator by emf and mmf method. Synchronous impedance method the synchronous impedance method or emf method is based on the concept of replacing the effect of armature reaction by an imaginary reactance. Electrical machinesiii important questions pdf file emiii imp qusts please find the attached pdf file of electrical machines iii important questions. To predetermine the efficiency and regulation of transformers and assess their performance. Elements of electrical engineering and electronics by v. Hence, the value or regulation so obtained is always more, than that found from an actual test. Electrical machinesiii important questions pdf file em. Why the bmw alternator is failed to charge there are certain components in your bmw that play a crucial role in the smooth running and better performance of the car.
A method known as the synchronous impedance test can be employed to determine these values. The voltage regulation of an alternator can be determined by different methods. Alternator working principle, emf equation of alternator, voltage regulation by sync. Voltage regulation of a synchronous generator direct. The synchronous impedance zs, found is always more than its value under normal voltage conditions and saturation. Which method for finding percentage regulation is called pessimistic method. Synchronization of two three phase alternators, by a synchroscope method b three dark lamp method c two bright one dark lamp method 6. Similarly measure the voltage across p and s fig b after joining the. Contents defination methods to determine voltage regulation 1 synchronous impedance method 2 mmf method 3 zero power factor method 3. Then the synchronous impedance of alternator will be a. The book principles of electrical machines book by vk mehta and rohit mehta is an ideal text for students who look to gain a current and clear understanding of the subject as all theories and concepts are explained with lucidity and clarity.
The alternator terminals are short circuited by closing tpst switch through an ammeter. Voltage regulation of an alternator is defined as the change in terminal voltage from no load to full load expressed as a percentage of rated voltage when the load at a given power factor is removed with out change in speed and excitation. Derivation of various power conditions in alternators and. Short questions and answers ee1251 electrical machines ii. Performance of synchronous generator connected to infinite bus, under constant. Thereactanceofarmaturereactionand regulation bytheoptimisticmethod 34. Why does the synchronous impedance method give a high value. Methods to determine voltage regulation of alternator. This is reality hence the results obtained by this method are nearer to the reality than those obtained by synchronous impedance method and ampereturns method. The following are the three methods which are used to predetermine the voltage regulation of smooth cylindrical type alternators synchronous impedance emf method. The main limitation of this method is that the method gives large values of synchronous reactance. Answer 8 armature reaction in an alternator mainly affects a rotor speed b. Name the various methods for predetermining the voltage regulation of 3phase alternator.
Regulation of an alternator to perform the opencircuit and shortcircuit tests on a three. The open circuit characteristic is the graph of the circuit voltage and the field current. One such system is the alternator which is used for generating the electricity for its electrical components as well as responsible for maintaining its battery charge. This mmf method is based on the results of open circuit test and short circuit test on an alternator. Synchronous impedance method armature turn or mmf method zero pf or potier method synchronous impedance method gives result which is higher than the original value. When an alternator is subjected to a varying load, the voltage at the armature terminals varies to a certain extent, and the amount of this variation determines the regulation of the machine. Modern power systems operate at some standard voltages. To perform this test, the output terminals of the alternator will be shorted by switch s.
A guide for synchronous generator parameters determination using dynamic simulations based on ieee standards conference paper pdf available october 2010 with 7,439 reads how we measure reads. The method requires following data to calculate the regulation. The oc and sc graphs are plotted from the two tests. The equipment working on these systems are therefore given input voltages at these standard values, within certain agreed tolerance limits. Voltage regulation synchronous generator or alternator. Feb 20, 2017 to measure negative sequence impedance of an alternator, we short the white and blue phases, measure the current and then divide it by the voltage of the red phase. Mmf method of voltage regulation its phasor diagram. To synchronise two 3phase alternator for parallel operation by a three lamp method, b. To start induction motor by rotor resistance starter 8. If you have more than 1 generator that normally operates interconnected with. This method takes into consideration the armature resistance an leakage reactance voltage drops as e. Negative and zero sequence impedance of alternator physics. The usual method of measuring synchronous impedance is by the short circuit test, which consists in running the alter nator at normal speed with its armature short circuited thru an ammeter and leads of negligible resistance and inductance. Regulation of alternator free download as word doc.
Jun 11, 2015 voltage regulation of an alternator is defined as the change in terminal voltage from no load to full load expressed as a percentage of rated voltage when the load at a given power factor is removed with out change in speed and excitation. The range of abnormal conditions and faults that can occur is extensive, and many could result in serious damage to the alternator and associated plant. The voltage regulation depends upon the power factor of the load. What are the methods for determining regulation of an alternator. To find the percentage regulation of 3phase alternator by synchronous impedance method at various power factor and load. Methods of finding voltage regulation in synchronous generator.
Which of the following method can be used to determined the voltage regulation of an alternoator. Voltage regulation of alternator and solved example ee academy. To understand the significance of regulation of an alternators using synchronous impedance method. Blondels two reaction theory, phasor diagram, direct axis and quadrature axis synchronous reactances, power angle characteristics, slip.
The regulation of a synchronous generator alternator is. Synchronous motor principle of operation, construction. Full text of the measurement of synchronous impedance. Calculating the shortcircuit current across the terminals of. Succinctly divided in 14 chapters, the book delves into important concepts of the subject which include armature reaction and commutation. The synchronous impedance method or emf method is based on the concept of replacing the effect of armature reaction by an imaginary reactance. Thetwocomponents,resistanceand inductance,form a resultantimpedancewhichmay be designated asthe workingimpedanceof the armature. In their case, standard construction consists of armature winding mounted on a stationary element called stator and field windings on a rotating element called rotor. In this method, the armature reaction is treated as another armature leakage reactance. This method requires following data to calculate the regulation. Apr 28, 2015 determination of voltage regulation method of synchronous machine 1.
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