Get the shortcircuit current i a,sc at that field current from the scc. Actual load need not be connected to the alternator and hence method can be used for very high capacity alternators. The open circuit emf e0 corresponding to the field current if is found from the open circuit. The main advantages of this method is the value of synchronous impedance z s for any load condition can be calculated. For calculating the regulation, the synchronous method requires the following data. Which of the method more accurate for determine the. The synchronous impedance method is based on the concept of replacing the effect of armature reaction by an imaginary reactance the magnetomotive force mmf. Novdec 2015 i synchronous impedance method or emf method ii ampere turns method or mmf method iii zero power factor method or potier triangle method iv asa modified form of mmf method v two reaction theory. 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. The regulation obtained by mmf method is less than that obtained by syn. Electrical machines ii emf induced in the armature. Potier method of predetermining the voltage regulation of an. It is clear that with change in load, there is a change in terminal voltage of an alternator. Synchronous machines notes part2 electric equipment.
A factor k d which is less than unity is therefore, introduced in the expression of emf. Voltage regulation of alternator by mmfampere turn method. Ee6504 electrical machines 2 question bank regulation 20. Write down the equation for frequency of emf induced in an alternator. Regulation of 3phase alternator by zpf and asa methods 9. 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. What is regulation of 3phase alternator by emf and mmf methods tabular. List out the different methods of finding the voltage regulation of an alternator. 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. What are the advantages and disadvantages of estimating the voltage regulation of an alternator by emf method. When we supply the magnetizing current by dc shunt generator through two slip rings in recent alternators, they use electronic starting system instead of slip rings and commutators because the field magnets are rotating. Electrical machines ii emf induced in the armature conductors. The aim of the experiment is to predetermine the regulation of three phase alternator by emf and mmf methods. Using the details it is possible determine the regulation at different power factors.
Which method gives the result nearer to the actual value. This mmf method is based on the results of open circuit test and short circuit test on an alternator. Ii performance of an alternator causes for voltage drop in alternators armature resistance, armature leakage reactance armature reaction, synchronous reactance, synchronous impedance, experimental determination phasor diagram of a loaded alternator. Mmf method of voltage regulation its phasor diagram. Regulation of 3phase alternator by emf and mmf methods page link. This gives the resultant field current if which would generate a voltage e 0 under no load conditions of the alternator. How to determine the regulation of an alternator by an asa method and what its difference with respect to other methods. C shunt motor 42 9 slip test on alternator 46 10 regulation of alternator by zpf method 52. Calcualte the percent line regulation posted 4 years ago. Voltage regulation of an alternator instrumentation tools.
A laboratory manual in electrical machines ii list of experiments regulation of three phase alternator by emf and mmf methods regulation of three phase alternator by zpf and asa methods regulation of three phase salient pole alternator by slip test measurements of negative sequence and zero sequence impedance of alternator v and inverted v curves of. But the drop due to armature resistance, leakage reactance is very small and can be neglected. Voltage regulation of alternator emf and mmf methods duration. Voltage regulation of an alternator electrical idea. An approximate method to determine the synchronous reactance x s at a given field current. Hence, its value is less than that due to a concentrated winding. Why is the mmf method of estimating the voltage regulation is considered as the. Get the internal generated voltage e a from the occ at that field current. The synchronous impedance method or emf method is based on the concept of replacing the effect of armature reaction by an imaginary reactance. The following are the three methods which are used to predetermine the voltage regulation of smooth cylindrical type alternators synchronous impedance emf method ampereturn mmf method potier zpf method 26. Short questions and answers ee1251 electrical machines ii.
May 28, 2018 modern power systems operate at some standard voltages. Blondels two reaction theory, phasor diagram, direct axis and quadrature axis synchronous reactances, power angle characteristics, slip test. Mention the methods by which voltage regulation can be determined. Hence regulation of the alternator at any load condition and load power factor can be determined. I f 22 i f2 t the regulation obtained by mmf method is less than that obtained by syn. 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. In this method also it is assumed that the magnetic circuit is unsaturated. The regulation of the alternator is found from the relation shown below. Figure 35 shows the complete phasor diagram for the mmf method.
Zero power factorzpf or potier triangle method for. Jun 04, 2015 voltage regulation it is clear that with change in load, there is a change in terminal voltage of an alternator. Mmf method for determining voltage regulation of alternator. The regulation curve is drawn between regulation and power factor viva questions. For any synchronous generator or alternator, mmf is required, which is a. Why is the mmf method of finding alternator voltage. Perform no load and short circuit tests on a threephase alternator. To calculate the voltage regulation by mmf method, the following information is required. Mmf method of voltage regulation its phasor diagram circuit. This zero power factor zpf method is used to determine the voltage regulation of synchronous generator or alternator. In short circuit test on synchronous machine field m. The open circuit emf e 0 corresponding to the field current if is. An alternator or ac generator dynamo is a device which convert mechanical energy to electrical energy. A single phase, 2000 v alternator has armature resistance and reactance of 0.
Aug 22, 2017 the voltage regulation calculated using mmf method will always be lower than actual voltage regulation of an alternator. Voltage regulation of alternator emf and mmf methods. Similar to emf method oc and sc characteristics are used for the determination of regulation by mmf method. Synchronization of two three phase alternators, by a synchroscope method b three dark lamp method c two bright one dark lamp method 6. Performance of synchronous generator connected to infinite bus, under constant power. Find out regulation of alternator by emf and mmf for full load at i unity p. Download as docx, pdf, txt or read online from scribd. Voltage regulation of alternator by mmf method voltage regulation of synchronous generator by mmf method. The value of the regulation not only depends on the load current but also on the power factor of the load. Differentiate mmf method from emf method of finding regulation of an alternator. The voltage regulation calculated using mmf method will always be lower than actual voltage regulation of an alternator. Mmf method of voltage regulation mmf method is also known as ampere turn 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. The emf equation for alternator can also be derived from the average voltage induced in armature.
For any synchronous generator or alternator, mmf is required, which is a product of. This method is based on the separation of armature leakage reactance drop and the armature reaction effect. This is more accurate than the emf and mmf methods. Slip test measurement of direct and quadrature axis reactance and predetermination of regulation of salient pole synchronous machines. Methods to determine voltage regulation of alternator. The regulation of a 3phase alternator may be predetermined by conducting the open circuit oc and the sort circuit sc tests.
Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on youtube. Voltage regulation of alternator by emf method and solved. Write a formal professional report, documenting all steps and replying to the questions clearly and neatly. In this method both the reactance drops are replaced by their equivalent mmfs. Figure shows the complete phasor diagram for the mmf method. The mmf method replaces the effect of armature leakage reactance by an. For finding voltage regulation of an alternator, the method which gives most accurate result is a. Which of the method more accurate for determine the voltage. What is the need for parallel operation of alternators.
The methods employed for determination of regulation are emf or synchronous impedance method, mmf or ampere turns method and the zpf or potier triangle method. Name the various methods for predetermining the voltage regulation of 3phase alternator. Mmf method of voltage regulation mmf method is also known as. A perphase equivalent circuit showing the induced emf in the armature winding due to the armature reaction. To start induction motor by rotor resistance starter 8. Jun 11, 2015 similar to emf method oc and sc characteristics are used for the determination of regulation by mmf method. To calculate voltage regulation of synchronous machine by m.
Zs at any load value can be determined so voltage regulation of alternator at any load condition and load power factor can be calculated. Using the details it is possible determine the regulation at different. The magnitude of this change depends not only on the load but also on the load power factor. Speed control of dc motor by armature voltage control and flux control. The voltage regulation of an alternator is defined as the rise in voltage when fullload is removed. Requirements for calculating voltage regulation by emf method or synchronous impedance method. Voltage regulation of synchronous machine alternator by. Voltage regulationemf, mmf, zpf and asa methods numerical problems.
To determine the regulation of a 3phase alternator by synchronous. With a distributed winding, the emf induced in the various coils constituting a group of coils are not in phase and so the total emf is the vector sum of all such emfs. The equipment working on these systems are therefore given input voltages at these standard values, within certain agreed tolerance limits. Do you need an answer to a question different from the above. Mar 28, 2015 in this method also it is assumed that the magnetic circuit is unsaturated. No title of the experiment page no 8 load test on a d. In this experiment, the emf and mmf methods are used. Modern power systems operate at some standard voltages. Measure the resistance of the stator armature winding of alternator. Apr 20, 2016 normally for voltage regulation calculation, we use methods like.