I1/I2 = ________I1/I3 = ________VCALCULATED VALUESMEASURED VALUESCALCULATED VALUESMEASURED VALUESCALCULATED VALUESMEASURED VALUESCALCULATED VALUESMEASURED VALUESCALCULATED VALUESMEASURED VALUESECE 4501 Power Systems Laboratory Manual Rev 1.04.0 TRANSFORMERS4.1 THE SINGLE PHASE TRANSFORMER4.1.1 OBJECTIVETo study the voltage and current ratios of a transformer and learn about exciting currents, volt-ampere capacity and short-circuit currents.4.1.2 DISCUSSIONTransformers are arguably the most universally applied pieces of electrical equipment. As such, they range in size from miniature units weighing ounces to huge units weighing tons. All transformers, however, exhibit the same basic properties.When mutual induction is permitted between two coils or windings, a change in current flowing through one coil induces a voltage upon the other coil. All transformers have a primary winding and one or more secondary windings. The electromagnetic coupling between the primary and secondary windings allows electrical energy to be transferred from the primary winding to the secondary winding. Electrical current entering the primary winding appears as an electromotive force (emf) at the secondary. Connecting the secondary winding to a load allows the energy to be transferred to the load. Since there is no electrical connection between primary and secondary windings (only a magnetic connection), the source and load can be electrically isolated from each other by means of a transformer.When a transformer is energized and loaded, AC current flowing in its windings creates an alternating magnetic field in its iron core. A small portion of the current, called the magnetizing current, is dedicated to the magnetic circuit in the creation of the magnetic field. Losses associated with the magnetizing current are reactive power (VARs). In addition, there are real power losses (Watts) in the transformer, associated with the inherent resistance in the windings (copper losses) and with eddy currents and hysteresis in the core (iron losses). For these reasons, the total power delivered to the primary side of the transformer is always larger than the total power available at the secondary side. Even so, it is still reasonable to say that energy is conserved in the transformer and that the real, reactive and apparent power applied to the primary of almost any transformer equals the real, reactive and apparent power available at the secondary.When the voltage applied to the primary winding is raised above rated value, the iron core begins to saturate, which leads to a rapid increase in the magnitude of the magnetizing current. Saturationof the core also distorts the sinusoidal voltage and current waveforms. The resulting harmonics can lead to mechanical resonances which, in large transformers, can be damaging. Transformers are also very susceptible to damage from short circuit currents.4.1.3 INSTRUMENTS AND COMPONENTSPower Supply Module EMS 8821Transformer Module EMS 8341AC Metering Module (2.5 A) EMS 8425AC Metering Module (250 V) EMS 84261ECE 4501 Power Systems Laboratory Manual Rev 1.0Ohmmeter ---4.1.4 PROCEDURECAUTION! – High voltages are present in this Experiment. DO NOT make any connections with the power supply ON. Get in the habit of turning OFF the power supply after every measurement.1) Examine the construction of the Transformer Module, EMS 8341, paying particular attention to the laminated steel core and the three windings.2) List the rated voltage for each of the three windings, list the rated voltage between each of the identified connection terminals, and list the rated current for each of the listed connections:Rated Voltage for Each Winding:Rated Voltage Between Connections:Rated Current Between Connections:Terminals 1 to 2: _______ V rmsTerminals 3 to 4: _______ V rmsTerminals 5 to 6: _______ V rmsTerminals 3 to 7: _______ V rmsTerminals 7 to 8: _______ V rmsTerminals 8 to 4: _______ V rmsTerminals 3 to 8: _______ V rmsTerminals 7 to 4: _______ V rmsTerminals 5 to 9: _______ V rmsTerminals 9 to 6: _______ V rmsTerminals 1 to 2: _______ A rmsTerminals 3 to 4: _______ A rmsTerminals 5 to 6: _______ A rmsTerminals 3 to 7: _______ A rmsTerminals 8 to 4: _______ A rms2ECE 4501 Power Systems Laboratory Manual Rev 1.03) Using an Ohmmeter, measure and record the DC resistance of each of the following windings:DC Resistance of each Transformer Winding:Terminals 1 to 2: _______ OhmsTerminals 3 to 4: _______ OhmsTerminals 3 to 7: _______ OhmsTerminals 7 to 8: _______ OhmsTerminals 8 to 4: _______ OhmsTerminals 5 to 6: _______ OhmsTerminals 5 to 9: _______ OhmsTerminals 9 to 6: _______ Ohms4) Now connect the following transformer circuit:Output Voltages:V 1 to 2: _______ V rmsV 3 to 4: _______ V rms V 5 to 6: _______ V rmsV 3 to 7: _______ V rmsV 7 to 8: _______ V rmsV 8 to 4: _______ V rmsV 5 to 9: _______ V rms3ECE 4501 Power Systems Laboratory Manual Rev 1.0V 9 to 6: _______ V rms5) Turn on the power supply and adjust the voltage control until the voltage, V4N, reads 120 V rms on the voltmeter module.6) Measure and record each of the output voltages listed above. Be sure to TURN OFF the power supply BEFORE changing the voltmeter leads.7) Measure and record the Ammeter reading: _________________ Amps8) Turn the voltage control knob to zero percent and turn OFF the power supply.9) Do the measured voltages correspond with the rated values? ________________10) What does the current measurement taken in step 7) represent? ________________________________________________________________________________________11)Windings 1 to 2 and 5 to 6 each have 500 turns of wire. Winding 3 to 4 has 865 turns. Calculate the following turns ratios:Turns ratio = N1/N2 = Winding 1 to 2 / Winding 5 to 6 = ____________Turns ratio = N1/N3 = Winding 1 to 2 / Winding 3 to 4 = ____________12) Now connect the circuit shown below. Notice that the second Ammeter provides a very low impedance (short circuit) path between terminals 5 and 6.Short Circuit Test 1:V1 = _______ V rmsI1 = _______ A rmsI2 = __0.4 __ A rmsCurrent Ratio:4ECE 4501 Power Systems Laboratory Manual Rev 1.0I1/I2 = ________13) Turn on the power supply and CAREFULLY increase