ELE-E502 TRANSFORMER OPEN CIRCUIT AND SHORT CIRCUIT TESTS
Read the test procedures before you come to the lab.
LabVolt Power Supply Module EMS 8821
Digital Energy Meter
LabVolt Transformer Module EMS 8341
On the transformer module, one side of the transformer will be winding 3-4; the other side of the transformer will be windings 1-2 and 5-6 connected in series so that the induced voltages add. In the following description, the winding 3-4 will be referred to as the low voltage winding (LV) and the winding 1-6 will be called the high voltage winding (HV).
1. Open Circuit Test
1.1 Connect the LV winding so that it is supplied by one of the variable line-to-line voltages. Insert instruments to measure the power to the transformer, voltage across the LV winding, and current into the transformer. Keep the terminals of the HV winding open. Draw the connection. Show the terminal numbers on all terminals.
1.2 Turn the power on. Adjust the voltage to its maximum (around 208 V). Read the instruments and record below.
Turn the voltage down to zero. Turn off the power
2. Short Circuit Test
2.1 Short circuit the LV winding. The HV winding will be connected to the power supply. Insert instruments to measure the power to the transformer, voltage across the HV winding, and current into the transformer on the HV side. Draw the connection. Show the terminal numbers on all terminals.
2.2 Turn the power on. Slowly rise to voltage until the rated current flows through the transformer HV winding. Read the instruments and record below.
3.1 From the above measured values, calculate the resistance representing the core losses Rc, the magnetizing reactance Xm, the winding resistance Req, and the winding reactance Xeq. State to which side of the transformer they are referred.
3.2 Refer all the resistances and reactances to the LV side. Draw the equivalent circuit.
3.3 Refer all the resistances and reactances to the HV side. Draw the equivalent circuit.
3.4 Calculate the per unit value for all resistances and reactances. Use the transformer ratings as the base. Draw the equivalent circuit.