In this topic, you study Three Phase Energy Meter – Working, Construction, Types & Diagram.
Three Phase Energy Meter is used for measuring the power consumption in kWh of a three phase electrical installation.
Types of Three phase Energy Meter
- Three-phase, Three-wire Energy Meter
- Three-phase, Four-wire Energy Meter
Three-phase, Three-wire Energy Meter
It is a combination of two single phase energy meters, as shown in Fig. 1. It consists of two pressure coils and two current coils and a single aluminium disc. The meter employs eddy current damping system by using a permanent horseshoe magnet. The meter is used on 3-phase balanced load circuit.
Fig. 1. 3-Phase, 3-Wire Energy Meter
The deflecting torque is the resultant of reaction between the fluxes of pressure and current coils connected to two phases, while the third phase is kept common. The counting mechanism mounted on the spindle gives kWh reading. Minor adjustment in the rotational speed of the disc can be made by adjusting the position of permanent magnet. The overall working of the meter is identical to that of a single phase energy meter.
Three-phase, Four-wire Energy Meter
It is also used for measuring kWh of a three phase electrical installation. It is a combination of three single phase energy meters; as shown in Fig. 2. It consists of three pressure coils and three separate aluminium discs one for each set of coils. The meter is capable to measure kWh of a three-phase unbalanced load circuit. The 3-phase 4-wire line can be used for power and light and fan purpose. All three aluminium discs are mounted on a single spindle. The counting mechanism mounted on the spindle gives kWh reading. The deflecting torque is the resultant of reaction between the fluxes of pressure and current coils connected to three phases. Minor adjustment in the rotational speed of the disc can be made by adjusting the positions of three permanent magnets, which provide eddy current damping to the meter. The overall working of the meter is identical to that of 3-phase 3-wire energy meter.
Fig. 1. 3-Phase, 4-Wire Energy Meter