Therefore the current through the current coil of the wattmeter will be equal to load current and the voltage across the pressure coil of. The pressure coil of both the wattmeters connects across the third phase say b.
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3 phase wattmeter connection diagram. The circuit diagram is shown below here it is applied to three phase four wire systems current coil of all the three wattmeters marked as 1 2 and 3 are connected to respective phases marked as 1 2 and 3. Connections of three phase wattmeter. In general m phase power can be measured by means of m 1 wattmeters. The method is valid for both balanced and unbalanced circuits with either the load or the source unbalanced. Such as system is shown in fig. Three wattmeter method of three phase power measurement.
This is known as the two wattmeter method of measuring three phase power. This point is often grounded at the supply for safety reasons. Figure 431 shows the connection diagram for the two wattmeter method of measuring three. This type of load is rarely found in practice because all the three wire star loads are balanced. Wye or star connection a three phase system with a common connection is normally drawn as shown in figure 5 and is known as a wye or star connection. Please not the connection of two wattmeters.
Consider the circuit has two wattmeters. The common point is called the neutral point. The connections for star connected loads for. Pressure coils of all the three wattmeters are connected to a common point at neutral line. The mutual interference between the elements of the three phase wattmeter will affect their accuracy. By correct connection we mean the current coil must be connected in series and the pressure coil must be connected in parallel to the load whose power is to be measuredideally current coil and pressure coil have zero and infinite resistance respectively.
However this method can also be employed in a 3 phase 3 wire delta connected load where power consumed by each load is required to be determined separately. 1 this only works as long as the voltages between themselves and the loads from the three phases are exactly the same. Three wattmeter method is employed to measure power in a 3 phase 4 wire system. Three wattmeter method is used to measure power in 3 phase 4 wire circuits. It is very obvious to measure the power of only a single phase and to multiply this by three to become the total power of the installation. This is irrespective of the circuit connection star or delta.
The current coil of both the wattmeter connects across any two phases say r and y. The circuit may be taken as balanced or unbalanced one balanced type being only a special case. In practice loads are not perfectly balanced and a fourth neutral wire is. Connection diagram to measure the three phase power with one wattmeter. The connection diagram for the measurement of power in three phase power measurement circuit using two wattmeters method is shown in figure 1. The figure below shows the three wattmeter connection of 3 phase 4 wire star connected load.
However this method can also be used in 3 phase 3 wire delta connected load where power consumed by each load is required to be determined separately. In a three phase four wire system if the connection between supply neutral and load neutral is broken it would result in an unbalanced three wire star load.
