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Unformatted text preview: Scott R. Smith ENEE473 Lab 4: Three-Phase Transformer March 2, 2007 Purpose: This experiment will show the differences between three-phase connections using three- phase transformers and resistive loads. The four configurations under consideration are shown below. No neutrals will be connected in this experiment. Y- Connection Y-Y Connection A A A A B B B B C C C C Figure 1 Figure 2 - Connection V-V Connection A A A A B B B B C C C C Figure 4 Figure 3 Devices and Instrumentation: Resistor Banks Each bank of resistors is made up of ten individual resistors that can be connected together using single pole double throw switches. By systematically setting the switches it is possible to create many resistance values by combining series and parallel branches in one bank. Each resistor has a power dissipation rating of 100 W and a resistance value of 250 . The power dissipation capacity can be increased by using parallel branches of resistors to achieve the same value as a series connection would. Multimeter The multimeter will mainly be used to check actual resistance values and measure voltages. Transformer There are three single-phase step-up transformers in the lab station. Each transformer is rated at 1 kW . The primary is on the left and secondary on the right. Wattmeter The wattmeter is a three-terminal device where two terminals are connected in-line with the circuit to measure current and the third terminal measures voltage of the in-line voltage relative to the connected node. There are two wattmeters at the lab station. Using both of them, three-phase power can be measured. Experimental Procedure: I. Voltage Measurement 1. Using the results from the winding sense test in lab 3, connect the transformers in the lab in the Y- configuration, as shown in figure 1. 2. Excite the primary winding up to 110 V per transformer leg using the three- phase voltage source. II. Y- Transformer 1. Using the Y- transformer configuration in figure 1, connect a balanced Y resistive load with each leg at 250 . No neutral should be connected. Be sure the dotted terminals are in the correct orientation....
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- Spring '07