What is Three Phase Energy Meter？
Definition
A three - phase energy meter is an instrument designed to measure the power of a three - phase electrical supply. It is constructed by connecting two single - phase meters via a shaft. The total energy consumption is determined by summing the readings of both elements.
Working Principle of Three - Phase Energy Meter
The torques generated by the two elements are mechanically combined. The total rotation of the shaft is directly proportional to the energy consumption of the three - phase system.
Construction of Three - Phase Energy Meter
The three - phase energy meter features two discs mounted on a common shaft. Each disc is equipped with a braking magnet, a copper ring, a shading band, and a compensator to ensure accurate readings. Two elements are employed to measure the three - phase power. The construction of the three - phase meter is illustrated in the figure below.
In a three - phase meter, the driving torques of the two elements need to be equal. This can be achieved by adjusting the torques. The adjustment is carried out by connecting the current coils of the two elements in series and their potential coils in parallel. When the full - load current passes through the coils, two opposing torques are generated within the coils.
Since the magnitudes of these two torques are equal, they prevent the disc from rotating. However, if the torques become unequal and the disc starts to rotate, the magnetic shunt is adjusted. Before testing the meter, a balanced torque must be obtained. To achieve this balanced torque, the positions of the compensator and the braking magnet for each element are adjusted separately.
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