The procedures to obtain the Full Load Cu loss and core loss of a Transformer

The copper loss of a transformer can be determined by short circuit test. In this test A watt meter W, voltmeter V and  an ammeter A are connected in the high  voltage winding. The low voltage winding is solidly short circuited by a thick conductor as shown in Fig 1.  A low voltage usually 5 to 10% of normal primary voltage at correct frequency is applied to the primary and is cautiously increased till full load currents are flowing both in primary and secondary. Since, in this test, the applied voltage is a small percentage of the normal voltage, the mutual flux ? produced is also a small percentage of its normal value. Hence core losses are very small with the result that the watt meter reading represent the full load Cu loss or I2R loss for the whole transformer i.e. both primary Cu loss and secondary Cu loss.    

 

                               

And the full load core loss of  a transformer can be determined by open circuit test. In this test A wattmeter W, voltmeter V and  an ammeter A are connected in the low voltage winding and the high voltage winding is open shown in fig2.  

                                    

With normal voltage applied to the primary , normal flux will be set up in the core, hence normal iron losses will occur which are recorded by the watt meter. As the primary no load current  I? is small, Cu loss is negligibly small in primary and nil in secondary. Hence the watt meter reading represents practically the core loss under no load condition