THREE PHASE CIRCUITSB. EXPERIMENTC. REPORTTHREE PHASE CIRCUITSA. PREPARATION1. Three Phase Voltages and Systems2. The Determination of Phase Sequence3. Blondel's Theorem and Its Consequences4. ReferencesB. EXPERIMENT1. Equipment List2. Three Phase Power Supply3. Balanced Three Phase Resistive Loads4. Unbalanced Three Phase Resistive Loads5. The Three Phase TransformerC. REPORT1. Three Phase Power Supply2. Balanced Three Phase Loads3. Unbalanced Three Phase Loads4. The Three Phase TransformerThree Phase Circuits - 1Three Phase Circuits - 21. Three Phase Voltages and SystemsThree Phase Circuits - 3Three Phase Circuits - 4Three Phase Circuits - 5Three Phase Circuits - 62. The Determination of Phase SequenceThree Phase Circuits - 7Three Phase Circuits - 83 Blondel’s Theorem and Its ConsequencesThree Phase Circuits - 9Three Phase Circuits - 104 ReferencesChapman, Stephen J., 2002. Electric Machinery and Power System Fundamentals. McGraw HillB. EXPERIMENT - THREE PHASE CIRCUITS1. Equipment Lista. The standard instrument rack found at each station.b. Various current shunts and probes. c. One single-phase wattmeter.d. One three-phase transformer.e. One Phase Sequence Indicator (PSI). f. One rheostat module with two 50- rheostats rated at 4.5 Amp each. g. Various power cords. 2. Three Phase Power Supply a. A schematic of the Phase Sequence Indicator (PSI) is provided on the next page.Plug this device into the Three Phase (3) wall power source using the 3-Phase Cord Set and determine the phase sequence (ABC or CBA) using the PSI. Be sure the switch is in the NORMAL position. Also, observe the Phase A and Phase B waveforms on the oscilloscope using two 10X Probes or the A/100 and B/100 test points with coaxial cables. Determine their phase relationship and thephase angle between them using the scope. Copy this display. Now repeat the above step for Phase A and Phase C and record the display. Next reverse the phase sequence by flipping the switch to REVERSE and observe the lamp pattern. Be sure and return the switch to the NORMAL position for the rest of theexperiment. Finally, observe the voltage waveform for the Star Point (STAR) on the Phase Sequence Indicator on the scope and copy this display. b. Being fully aware of the potential for an electric shock, and therefore careful to shut off the 3-phase breaker each time the DMM connections are moved, accurately measure the rms values for the three line-to-line voltages and the three line-to-neutral voltages at your station using three DMMs. c. The "green" neutral wire on the 3-phase supply provides a return to ground. It is well and thoroughly grounded and will remain at Mother Earth potential as long as there is no IR voltage drop, i.e, as long as the neutral return current is zero. This is the case for perfectly balanced three phase voltage sources and perfectly Three Phase Circuits - 11Three Phase Circuits - 12Input Phase CBAInput Phase ABCNormalReverseBACA CBbalanced loads since no neutral current will exist to produce an IR voltage drop. Using a coaxial cable, determine the existence of any neutral point offsets by observing on the scope the voltage waveform between the Neutral Point (N) on the Phase Sequence Indicator and the "green" ground on its chassis and copy your observation. Note that the scope is already referenced to ”green” ground. 3. Balanced Three Phase Resistive Loadsa. Using a DMM to measure the left and right side resistances of the left rheostat, adjust it to make 2 equal resistances of approximately 25  each. Record the 2 resistance values. Now adjust the right rheostat until its left side resistance is equal to the two left rheostat resistances and record its value. Now connect these three equal resistances to form a balanced Three Phase (3) Wye load by connecting the yellow receptacles on the rheostats to form a load resistance Common Point (O). Connect the left side of the left rheostat to the Phase A output of the Phase Sequence Indicator (PSI) and the right side to the Phase B output of the PSI. Connect the left side of the right rheostat to the Phase C output of the PSI. Connect the rheostat Common Point (O) to the Neutral Point (N) of the PSI to form a Neutral Return line. Show your set-up to the instructor.b. Now instrument the set-up, using 3 DMMs and 1 Wattmetter, to measure Phase Aline current (IA), Phase A load voltage (VAO), Phase A load power (PAO), and Neutral Return line current (ION). Use current shunts as required. Use a 10x probe to observe Phase A rms voltage (VAG) and a coaxial cable to observe the rheostat Common Point (O) rms voltage (VOG). Show your set-up to the instructorbefore turning on 3 power. Once your set-up is approved by the instructor, turn on 3 power and record all measurements and copy the scope display. With power on, carefully move the 10X probe to also measure Phase B (VBG) and Phase C (VCG) rms voltages. Separately record these rms measurements. Turn off 3 power when finished recording all measurements. c. Now remove the “O” to “N” Neutral Return wire and change the DMM being used to measure Neutral Return current to now measure rheostat Common Point (O) rms voltage (VON) relative to the Neutral Point (N) on the PSI. Turn on 3 power and record all measurements. Turn off 3 power when finished.Three Phase Circuits - 134. Unbalanced Three Phase Resistive Loadsa. Now disconnect the Phase A and Phase B leads from the left rheostat. Connect a DMM to the left side of the left rheostat and adjust this rheostat until a resistance of 15  is obtained. Measure and record both of the left rheostat resistances. Now reconnect the circuit as it was in Part B.3.c. above and show it to the instructor. When approved by the instructor, turn on 3 power and record all DMM and wattmeter measurements. Turn off 3 power when finished.b. Obtain a second Wattmeter and reconfigure the instrumentation to measure load power using the 2 wattmeter method. Configure the DMMs to measure the three load voltages relative to the rheostat Common Point (O). Show this set-up to the instructor. When approved, turn on 3 power and record the measured powers and load voltages. Be sure that both Wattmeters read upscale. Turn off 3 power when finished.c. Remove both Wattmeters from the circuit and reconnect the Neutral Return wire between the rheostat Common Point and the Neutral Point of the PSI.