File Name: voltage regulation of alternator by emf and mmf method .zip
The OC and SC graphs are plotted from the two tests. The synchronous impedance is found from the OC test. The regulation is then determined at different power factors by calculations using vector diagrams.
The EMF method is also called pessimistic method as the value of regulation obtained is much more than the actual value. The MMF method is also called optimistic method as the value of regulation obtained is much less than the actual value. In the MMF method the armature leakage reactance is treated as an additional armature reaction. In both methods the OC and SC test data are utilized. The alternator field potential divider should be kept in the minimum voltage position.
Initially all switches are in open position. Note down the name plate details of the motor and alternator. Connections are made as per the circuit diagram.
Using the Three point starter, start the motor to run at the synchronous speed by adjusting the motor field rheostat. Conduct Open Circuit test by varying the potential divider for various values of field current and tabulate the corresponding Open Circuit Voltage readings. Conduct Short Circuit test by closing the TPST switch and adjust the potential divider to set the rated armature current and tabulate the corresponding field current.
The Stator resistance per phase is determined by connecting any one phase stator winding of the alternator as per the circuit diagram using MC voltmeter and ammeter of suitable ranges.
From the graph find the open circuit voltage per phase E1 ph for the rated short circuit current Isc. By using respective formulae find the Zs, Xs, Eo and percentage regulation. Draw the line OL to represent. Open circuit voltage for lagging p. Open circuit voltage for leading p. Open circuit voltage for unity p. What is meant by voltage regulation? What is meant by Synchronous Impedance?
What is OC test? What is SC test? What is meant by mmf or field ampere turns? Open navigation menu. Close suggestions Search Search.
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Facebook Twitter. This MMF method is based on the results of open circuit test and short circuit test on an alternator. For any synchronous generator or alternator, MMF is required, which is a product of field current and turns of the field winding for two separate purposes. It must have an MMF necessary to induce the rated terminal voltage on the open circuit. Key Point: In most of the cases, as the number of turns on the field winding is not known, the MMF is calculated and expressed in terms of the field current itself. The field mmf which is required for inducing the rated terminal voltage on the open circuit can be obtained from open circuit test results and open circuit characteristics. This is denoted as F O.
The voltage regulation of alternator by EMF method involves the EMF quantities of all the armature parameters armature resistance, Armature leakage reactance, armature reaction. The drop due to armature reaction is not considered, because it does not occur due to any of the physical element but due to interaction of armature flux with main flux. Now, the Sum of armature leakage reactance and armature reaction reactance is called synchronous reactance of an alternator X S. In EMF method, the voltage drop due to armature resistance R a and the drop due to synchronous reactance X S is considered, both the drops are emf quantities. This method is also called pessimistic method , because the voltage regulation obtained by this method is more than the actual value.
This method of finding voltage regulation considers the opposite view to the synchronous impedance method. It assumes the armature leakage reactance to be additional armature reaction. Neglecting armature resistance always small , this method assumes that change in terminal p. The same two tests viz open-circuit and short-circuit test are required as for synchronous reactance determination; the interpretation of the results only is different. Hence the armature reaction is entirely demagnetizing. Since the terminal p.
Voltage regulation of an alternator by emf and mmf methods. Voltage regulation of an alternator instrumentation tools. To calculate the voltage regulation by mmf method, the following information is required. How to determine the regulation of an alternator by an asa method and what its difference with respect to other methods.
The voltage regulation of alternator by EMF method involves the EMF quantities of all the armature parameters armature resistance, Armature leakage reactance, armature reaction. The drop due to armature reaction is not considered, because it does not occur due to any of the physical element but due to interaction of armature flux with main flux. Now, the Sum of armature leakage reactance and armature reaction reactance is called synchronous reactance of an alternator X S. In EMF method, the voltage drop due to armature resistance R a and the drop due to synchronous reactance X S is considered, both the drops are emf quantities. This method is also called pessimistic method , because the voltage regulation obtained by this method is more than the actual value. Armature Resistance per phase can be obtained by conducting stator resistance test on the alternator. It is done by connecting the dc voltage supply to the stator armature winding and the corresponding current is measured.
Facebook Twitter. This method is also known as EMF method. Before calculating the voltage regulation we need to calculate the following data. Armature Resistance per phase [R a ].
voltage regulation, EMF method, MMF method, modified MMF method, ZPF method, power angle E.M.F. equation of an elementary alternator three phase.Reply
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The OC and SC graphs are plotted from the two tests.Reply