Experiment_6_Three-Phase_Power_Measurement - Experiment 6...

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6 1 Experiment 6 Three-Phase Power Measurement OBJECTIVE To measure power in a three-phase circuit using the two wattmeter method. To determine the active, reactive power, and the power factor of a three-phase system. DISCUSSION A wattmeter, used for measuring power, is an electrodynamometer type instrument. This meter usually has two coils, one fixed, the other capable of turning in the magnetic field of the first. The fixed coil is connected in series with the line so as to carry the line current. The movable coil, which is of high resistance, is connected across the load (that portion of the circuit in which the power is to be measured). The small current in the coil is, therefore, proportional to the voltage between these terminals. This coil turns against a helical spring, and, since toque is proportional to the product of the values of the currents in the two coils, it is proportional to the product of the current I and the voltage E. The scale may, therefore, be graduated directly in watts. See Figure 6-1. The fixed current coil A is in series with the load, and the movable voltage coil V is across load. The resulting deflection is directly proportional to the active power delivered to the load. Figure 6-1
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6 2 If the power delivered by a three-phase, four-wire system is to be measured, we simply use three
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Experiment_6_Three-Phase_Power_Measurement - Experiment 6...

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