22-09-2012, 10:33 AM
Single Phase Transformer
1Single Phase.docx (Size: 362.4 KB / Downloads: 91)
O.C. and S.C. Tests on Single Phase Transformer
The efficiency and regulation of a transformer on any load condition and at any power factor condition can be predetermined by indirect loading method. In this method, the actual load is not used on transformer. But the equivalent circuit parameters of a transformer are determined by conducting two tests on a transformer which are,
1. Open circuit test (O.C Test)
2. Short circuit test (S.C.Test)
The parameters calculated from these test results are effective in determining the regulation and efficiency of a transformer at any load and power factor condition, without actually loading the transformer. The advantage of this method is that without much power loss the tests can be performed and results can be obtained. Let us discuss in detail how to perform these tests and how to use the results to calculate equivalent circuit parameters.
Open Circuit Test (O.C. Test)
The transformer primary is connected to a.c. supply through ammeter, wattmeter and variac. The secondary of transformer is kept open. Usually low voltage side is used as primary and high voltage side as secondary to conduct O.C test.
The primary is excited by rated voltage, which is adjusted precisely with the help of a variac. The wattmeter measures input power. The ammeter measures input current. The voltemeter gives the value of rated primary voltage applied at rated frequency.
Sometimes a voltmeter may be connected across secondary to measure secondary voltage which is V2 = E2 when primary is supplied with rated voltage. As voltmeter resistance is very high, though voltmeter is connected, secondary is treated to be open circuit as voltmeter current is always negligibly small.
When the primary voltage is adjusted to its rated value with the help of variac, readings of ammeter and wattmeter are to be recorded. The observation table is as follows
1Single Phase.docx (Size: 362.4 KB / Downloads: 91)
O.C. and S.C. Tests on Single Phase Transformer
The efficiency and regulation of a transformer on any load condition and at any power factor condition can be predetermined by indirect loading method. In this method, the actual load is not used on transformer. But the equivalent circuit parameters of a transformer are determined by conducting two tests on a transformer which are,
1. Open circuit test (O.C Test)
2. Short circuit test (S.C.Test)
The parameters calculated from these test results are effective in determining the regulation and efficiency of a transformer at any load and power factor condition, without actually loading the transformer. The advantage of this method is that without much power loss the tests can be performed and results can be obtained. Let us discuss in detail how to perform these tests and how to use the results to calculate equivalent circuit parameters.
Open Circuit Test (O.C. Test)
The transformer primary is connected to a.c. supply through ammeter, wattmeter and variac. The secondary of transformer is kept open. Usually low voltage side is used as primary and high voltage side as secondary to conduct O.C test.
The primary is excited by rated voltage, which is adjusted precisely with the help of a variac. The wattmeter measures input power. The ammeter measures input current. The voltemeter gives the value of rated primary voltage applied at rated frequency.
Sometimes a voltmeter may be connected across secondary to measure secondary voltage which is V2 = E2 when primary is supplied with rated voltage. As voltmeter resistance is very high, though voltmeter is connected, secondary is treated to be open circuit as voltmeter current is always negligibly small.
When the primary voltage is adjusted to its rated value with the help of variac, readings of ammeter and wattmeter are to be recorded. The observation table is as follows