Electrical Engineering ⇒ Topic : Power Measurement in 3phase Circuits

Daniel
 
Power Measurement in 3phase Circuits At first glance, the measurement of the power drawn by a 3phase load seems to be a simple problem. We need place only one wattmeter in each of the three phases and add the three readings algebraically to obtain the total power. This procedure for the measurement of power in a 3phase circuit is certainly impracticable if not impossible. It is because the neutral of a Yconnected load is usually not accessible and the phases of Δconnected load are not available for insertion of wattmeter in each phase. Inmost of the *practical 3phase circuits, only three line terminals are available. It is obvious that we need a method for measuring the total power drawn by a 3phase load having only three accessible terminals (i.e. the three lines). Two such methods available are (i) Threewattmeter method (ii) Twowattmeter method Both these methods can measure power in a 3phase load (Y or Δ) whether the load is balanced or not. The twowattmeter method is widely used for the measurement of 3phase power due to its many advantages. Note. If the load is balanced, the power in any phase can be measured by a single wattmeter. The total circuit power is given by multiplying the wattmeter reading by three. This method can only be used if the load is balanced. Its principal disadvantage is that it is not always possible to make the required connections  
 
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