Voltage regulation of a synchronous generator direct. Nov 22, 2015 voltage regulation of alternator and solved example ee academy. Why is the synchronous impedance method of estimating voltage regulation considered as pessimistic method. The voltage regulation of a threephase alternator can also be determined using the synchronous impedance method. For proper parallel operation, 3phase alternators must have the same a speed. It is conducting oc and sc tests on the given three phase alternator and determining the regulation by synchronous impedance. Hence, the value or regulation so obtained is always more, than that found from an actual test. Methods to determine voltage regulation of alternator. A no load voltage is induced in the stator coils of alternator when rotor is rotated by a prime mover. Synchronous impedance of a wyeconnected alternator. The voltage regulation of an alternator is defined as the change in its terminal voltage when the full load is removed, keeping field excitation and speed constant, divided by the rated terminal voltage. Voltage regulation of alternator using synchronous.
Normally for voltage regulation calculation, we use methods like. Which method gives the result nearer to the actual value. 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. What is regulation of alternator by synchronous impedance method.
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. Voltage regulation of alternator emf and mmf methods. Electric utilities aim to provide service to customers at a specific voltage level, for example, 220 v or 240 v. This method is also known as amp turns cedure can be used for determination of regulation by mmf method. 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.
Voltage regulation of alternator using synchronous impedance method voltage regulation of synchronous generator calculations. Voltage regulation of synchronous generator by mmf method. Sm23 synchronous impedance method or emf method duration. Or the numerical value of the regulation is defined as the percentage rise in voltage when full load at. Factors affecting alternator size alternator on load synchronous reactance vector diagrams of loaded alternator voltage regulation rotherts m.
Which of the method more accurate for determine the voltage. 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. They are named as direct load test method and indirect methods of voltage regulation. Voltage regulation of an alternator electrical idea. Voltage regulation of alternator using synchronous impedance. This method requires following data to calculate the regulation. Synchronous machines notes part2 electric equipment. What is synchronous generator asynchronous generator. The open circuit voltage and short circuit current of a 3 phase, star connected alternator are 1050 v and 250 a respectively. However, due to kirchhoffs laws, the voltage magnitude and thus the service voltage to customers will in fact vary along the length of a conductor such as a distribution feeder see electric power distribution. Name the various methods for predetermining the voltage regulation of 3phase alternator. Figure 1224 shows the circuit used to determine the synchronous impedance of a wyeconnected ac generator.
A synchronous generator operating at a leading power factor often has a negative voltage regulation. Why is the synchronous impedance method of estimating voltage regulation is considered as pessimistic method. Voltage regulation of synchronous generator using emf method. This procedure is continued until the alternator voltage is 120% of its rated voltage. 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. The indirect method is further classified as synchronous impedance method, ampereturn method and zero power factor method. In the before methods that is voltage regulation of synchronous machine by e. Mar 28, 2015 calculate the voltage regulation at a 0. The method requires following data to calculate the regulation.
Thetwocomponents,resistanceand inductance,form a resultantimpedancewhichmay be designated asthe workingimpedanceof the armature. They supply the electric power used by all sectors of modern societies. The voltage regulation depends upon the power factor of the load. For finding voltage regulation of an alternator, the method which gives most accurate result is a. Regulation obtained by using a synchronous impedance method is higher than that obtained by actual loading. Estimation of optimal value of synchronous impedance using. Short questions and answers ee1251 electrical machines ii. This mmf method is based on the results of open circuit test and short circuit test on an alternator. The value of the regulation not only depends on the load current but also on the power factor of the load. C armature windings armature winding of alternator winding factors e. Voltage regulation of synchronous machine alternator by. Then the synchronous impedance of alternator will be a. The synchronous impedance of cylindrical rotor alternator is estimated based on the equivalent circuit model and voltage regulation. Synchronous generator is one of the most commonly used alternators.
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. The synchronous impedance method or emf method is based on the concept of replacing the effect of armature reaction by an imaginary reactance. Dec 07, 2019 this change in the terminal voltage is significant in defining the voltage regulation. According to the structure, it can be divided into two types. Dec 18, 2018 synchronous generator, that is, an alternator ac generator with the same rotor speed as the rotating magnetic field of the stator. 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. Voltage regulation of alternator and solved example youtube.
This change in the terminal voltage is significant in defining the voltage regulation. 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. Now lets calculate voltage regulation of synchronous machine by e. Apr 20, 2016 normally for voltage regulation calculation, we use methods like. Hence, this method is also called the pessimistic method. Mmf method for determining voltage regulation of alternator. F equation of an alternator armature reaction in alternator alternator on load synchronous reactance x s phasor diagram of a loaded alternator voltage.
Blondels two reaction theory, phasor diagram, direct axis and quadrature axis synchronous reactances, power angle characteristics, slip test. The synchronous impedance zs, found is always more than its value under normal voltage conditions and saturation. Contents defination methods to determine voltage regulation 1 synchronous impedance method 2 mmf method 3 zero power factor method 3. The regulation of a 3phase alternator may be predetermined by conducting the open circuit oc and the sort circuit sc tests. Pdf principles of electrical machines book by vk mehta and. Method of synchronization of an alternator answers. Before calculating the voltage regulation we need to calculate the following data. Jun 04, 2015 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. The regulation curve is drawn between regulation and power factor viva questions. Electrical machines short answers instrumentation tools. Pdf a new approach for synchronous generator terminal. Dc resistance test, e between line 6 v dc, i in lines 10 a dc. Alternator construction of alternator alternation operation frequency a.
A convenient way to compare the voltage behaviour of two generators is by their voltage regulation vr. And determine the full load regulation of a three phase synchronous generator by synchronous impedance method 3. Blondels two reaction theory, phasor diagram, direct axis and quadrature axis synchronous reactances, power angle characteristics, slip. Voltage regulation of alternator and solved example ee academy. In this page you can learn various important alternator multiple choice questions answers,alternator mcq,sloved alternator objective questions answers, alternator mcq pdf etc.
At unity load power factor, the effect of armature reaction on the mainfield flux of an alternator is a nominal. Jun 11, 2015 voltage regulation of synchronous generator by mmf method. There are mainly two methods which are used to determine the regulation of voltage of a smooth cylindrical rotor type alternators. Generally, we use this synchronous impedance method for highspeed alternators or synchronous generator. 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. Full text of the measurement of synchronous impedance. Solved regulation of alternator by synchronous impedance. Genetic algorithm based impedance estimation technique is adopted, where only machine rating is used. Since the armature reactance cannot be controlled, an obvious approach to adjust the terminal voltage is by controlling the internal generated. The field excitation is varied upto the rated voltage.
Voltage regulation of alternator by mmfampere turn method. Alternator multiple choice questions mcq and answers. 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. Normally, a constant terminal voltage supplied by a generator is desired. To study and measure direct and quadrature axis reactance of a 3 phase alternator by slip test 4. Zero power factor zpf methodpotier triangle method of. Why is the mmf method of estimating the voltage regulation is. 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. Mention the methods by which voltage regulation can be determined. To calculate voltage regulation of synchronous machine by m. In this experiment, the emf and mmf methods are used. Voltage regulation of alternator by emf method and solved.
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