Experiment_1_The_Wattmeter

# Experiment_1_The_Wattmeter - Experiment 1 The Wattmeter...

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1 1 Experiment 1 The Wattmeter OBJECTIVE To learn how to use a wattmeter. To become familiar with active and apparent power in AC circuits. DISCUSSION In direct current (DC) circuits, the power (in watts) supplied to a resistive load is always equal to the product of the voltage and the current. In alternating current (AC) circuits, the product of the voltage and the current does not always give an answer which can be stated in watts. For this reason, wattmeters are essential in AC circuits, so that the active power (in watts) may be measured. Apparent power (in volt-amperes) is defined as the product of the AC voltage and the AC current. Apparent power is only equal to active power when the load circuit is entirely resistive. When the load circuit is not entirely resistive, the apparent power (VA) can be quite different from the active power (W). It is a little early to explain why this is so, but we will shortly explain the phenomenon. At present, we will perform some experiments to show what we mean by active and apparent power, and how these powers can be measured. EQUIPMENT REQUIRED Workstation AC power supply, Single-Phase Wattmeter, AC Voltmeter, AC Ammeter, Resistance Module, Inductance Module, Capacitance Module PROCEDURE CAUTION! High voltages are present in this Experiment! Do not make or modify any banana jack connections with the power on unless otherwise specified!

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1 2 The grading in this section is 1 point for each correct answer. 1. Examine the construction of the Single-Phase Wattmeter. Pay particular attention to the meter, connection terminals and the wiring. The module wiring schematic is shown in Figure 1-1. Figure 1-1 The internal meter current coil connections are brought out to meter terminals A and B. The internal meter voltage coil connections are brought out to meter terminals C and D. The current coil (protected by the diodes) is connected in series with the line (module terminals 1 and 3). The voltmeter coil is connected in parallel across the load side of the line (module
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Experiment_1_The_Wattmeter - Experiment 1 The Wattmeter...

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