The voltage regulation depends upon the power factor of the load. Voltage regulation of an alternator electrical idea. And determine the full load regulation of a three phase synchronous generator by synchronous impedance method 3. It will be found that all these methods differ chiefly in the way the noload voltage e0 is found in each case. Explain the effect of change of excitation of a synchronous motor on its power factor. In this method both the reactance drops are replaced by their equivalent mmfs. 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.
Electrical machines 2 important questions ee8401 pdf free. The rotation of field poles in the presence of armature conductors induces an alternating voltage which results in electrical power generation. Explain the effect of change of excitation of a synchronous motor on its armature current. Which of the method more accurate for determine the.
The open circuit characteristic is the graph of the circuit. 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. To deliver equal power through line 1 and line 2 the phase and active component of line current i 1 and i 2 must be equal to compensate impedance drop the regulating components re are installed at the sending end of each transmission line. 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. Why is the synchronous impedance method of estimating voltage regulation considered as pessimistic method. Short questions and answers ee1251 electrical machines ii.
For high capacity alternators, which method is not suitable for finding percentage regulation. This mmf method is based on the results of open circuit test and short circuit test on an alternator. Adams engineering college, paloncha eee department emii lab experiment no. Mmf method for determining voltage regulation of alternator. The synchronous impedance zs, found is always more than its value under normal voltage conditions and saturation. Voltage regulation of synchronous machine alternator by. Voltage regulation of alternator and solved example youtube. Explain synchronous impedance method for determining regulation of an alternator. Protection of synchronous generators involves the consideration of faults and harmful abnormal operating conditions, more so than the protection of other power system elements. In short circuit test on synchronous machine field m. 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. To verify kirchhoffs voltage and current law in a passive resistive network. Synchronous alternator protection principles and systems. To start induction motor by rotor resistance starter 8.
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. For unity and lagging power factors, there is always a voltage drop with the increase of load, but for a. Ee8401 important questions electrical machines 2 regulation 2017 anna university free download. Voltage regulation of alternator by emf method and solved.
Regulation of 3phase alternator by zpf and asa methods 9. Synchronous impedance then, synchronous reactance, fig 5 shows the phasor diagram of the alternator, supplying full load current of i a ampere, lagging the terminal voltage v by an angle. The regulation of a synchronous generator alternator is. Efficiency of an alternator is calculated by measurement of losses method. Voltage regulation of synchronous machine is defined as the difference between terminal voltage at no load and terminal voltage at full load and excitation, speed must remain same. Alternators electrical engineering questions and answers. The rotor part consists of field poles and stator part consists of armature conductors. 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.
Electrical machines short answers instrumentation tools. But the drop due to armature resistance, leakage reactance is very small and can be neglected. A convenient way to compare the voltage behaviour of two generators is by their voltage regulation vr. Thetwocomponents,resistanceand inductance,form a resultantimpedancewhichmay be designated asthe workingimpedanceof the armature. Voltage regulation of a synchronous generator the voltage regulation of a synchronous 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. It is used because the motor is calibrated in the sense that all it losses have been determined for varying condition of operations so that its output is then readily be obtained. Alternator if there are n ph turns per phase, then synchronous generator e ph 4. To pre determine the regulation of an alternator at full load at different power factors using synchronous impedance and mmf methods. 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. The method requires following data to calculate the regulation. To study and measure positive, negative and zero sequence. Hence, other indirect methods are used as discussed below. Few requirements are there to calculate voltage regulation of synchronous machine by e. Blondels two reaction theory, phasor diagram, direct axis and quadrature axis synchronous reactances, power angle characteristics, slip test.
Voltage regulation of alternator by mmfampere turn method. Voltage regulation of alternator using synchronous. Voltage regulation of alternator emf and mmf methods. 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 a synchronous generator direct. Pdf principles of electrical machines book by vk mehta. Synchronization of two three phase alternators, by a synchroscope method b three dark lamp method c two bright one dark lamp method 6. What are the special applications of an over excited synchronous motor. Voltage regulation of alternator using synchronous impedance method voltage regulation of synchronous generator calculations. A no load voltage is induced in the stator coils of alternator when rotor is rotated by a prime mover. Succinctly divided in 14 chapters, the book delves into important concepts of the subject which include armature reaction and commutation. There are various methods for determination of regulation one of them is synchronous impedance method is based on the concept of. The open circuit voltage e 0 of the alternator is given by, phosor sum the diagram has been drawn with the current as the reference phasor and is self explanatory. Electrical machinesii lab manual pdf emii lab manual pdf. The following are the three methods which are used to predetermine the voltage regulation of smooth cylindrical type alternators.
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. The synchronous impedance method or emf method is based on the concept of replacing the effect of armature reaction by an imaginary reactance. With what condition synchronous motor can be used as a synchronous condenser. For calculating the regulation, the synchronous method requires the following data. Synchronous impedance method of finding voltage regulation of an alternator is called pessimistic method because a. Figure shows the complete phasor diagram for the mmf method. Voltage regulation of synchronous machine is generally calculated in percentage of full load terminal voltage. Voltage regulation of alternator emf and mmf methods duration. The alternator terminals are short circuited by closing tpst switch through an ammeter. Voltage regulation of synchronous machines alternator by. Electrical machinesii lab manual pdf emii lab manual pdf file please download the electrical machinesii lab manual pdf emii lab manual pdf file in t. 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. They supply the electric power used by all sectors of modern societies. Then the synchronous impedance of alternator will be a.
The open circuit voltage and short circuit current of a 3 phase, star connected alternator are 1050 v and 250 a respectively. Contents defination methods to determine voltage regulation 1 synchronous impedance method 2 mmf method 3 zero power factor method 3. Synchronous generator construction and working principle. Objective questions on alternator page 2 electrical. Full text of the measurement of synchronous impedance. Consider the 2 generating station s1 and s2 supplying a receiving station rs through line 1 and line 2. Ee8401 question paper electrical machines 2 regulation 2017. Synchronous impedance method or emf method ii ampere turns method or mmf method iii zero power factor method or potier triangle method iv. Electrical and electronics engineering lab manual pdf. To study and measure direct and quadrature axis reactance of a 3 phase alternator by slip test 4. Voltage regulation of transformer plz use speakers.
Normally for voltage regulation calculation, we use methods like. In general, synchronous generator consists of two parts rotor and stator. Blondels two reaction theory, phasor diagram, direct axis and quadrature axis synchronous reactances, power angle characteristics, slip. Now lets calculate voltage regulation of synchronous machine by e. For any synchronous generator or alternator, mmf is required, which is a. Thereactanceofarmaturereactionand regulationbytheoptimisticmethod 34. A quite accurate and simple method of determining the losses is to use a calibrated d.
Name the various methods for predetermining the voltage regulation of 3phase alternator. In this method also it is assumed that the magnetic circuit is unsaturated. Methods to determine voltage regulation of alternator. 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. Alternator on load synchronous reactance vector diagrams of loaded alternator voltage regulation rotherts m. Hence, the value or regulation so obtained is always more, than that found from an actual test.
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