Wiring Method and Working Principle of Single-Phase Watt-Hour Meter
Single-phase electric energy meter, used in active energy measurement. Accurate measurement, modular and small size (18mm), can be easily installed in various terminal distribution boxes. DIN-rail mounting, bottom wiring, perfectly matched with miniature circuit breakers. Intuitive and easy-to-read mechanical display reduces the risk of data loss in unexpected power outages. No external operating power supply is required. Wide operating temperature range.
The single-phase watt-hour meter is a kind of watt-hour meter. The main structure of the watt-hour meter is composed of a voltage coil, a current coil, a turntable, a rotating shaft, a brake magnet, a gear, and a meter. Single-phase meters are generally used for civilian use, connected to 220V equipment. The watt-hour meter uses the eddy current generated by the voltage and current coils on the aluminum plate to interact with the alternating magnetic flux to generate electromagnetic force to make the aluminum plate rotate. At the same time, the braking torque is introduced, so that the speed of the aluminum disc is proportional to the load power. Through the axial gear transmission, the electric energy is measured by accumulating the number of revolutions of the turntable by the counter.
Principle of watt-hour meter:
When the watt-hour meter is connected to the circuit under test, the voltage U of the circuit under test is applied to the voltage coil, forming an alternating magnetic flux in its iron core. Part of this flux, ΦU, passes through the aluminum disk from the return pole to the iron core back to the voltage coil. Similarly, after the current I of the circuit under test passes through the current coil, an alternating magnetic flux Φi is also formed in the U-shaped iron core of the current coil. This magnetic flux is formed by the U-shaped end of the iron core and passes through the aluminum disk from bottom to top, and then passes through the aluminum disk from top to bottom and returns to the other end of the U-shaped iron core.
The return magnet plate 4 is punched from a steel plate, and its lower end extends into the lower part of the aluminum plate, corresponding to the iron core column separated by the aluminum plate and the voltage component, so as to form a circuit of the working magnetic flux of the voltage coil. Since the two magnetic fluxes passing through the aluminum disk are alternating magnetic fluxes and pass through the aluminum disk at different positions, induced eddy currents are generated near the respective positions where they pass through the aluminum disk. The interaction of the two magnetic fluxes with these eddy currents produces a rotational torque on the aluminum disk that pushes the aluminum disk to rotate.
Single-phase watt-hour meter wiring method:
There are two wiring methods for the watt-hour meter: jump-in connection and shun-in connection;
These two wiring methods are not the same on the surface, but the internal principle is the same, that is, the current coil of the ammeter is connected in series with the load loop. While the voltage coil is connected in parallel with the load, the "*" end of the two coils should be connected to the same polarity end of the power supply. Generally, a single-phase watt-hour meter has a special junction box. When you open the box cover, you can see that there are four terminal buttons. The actual wiring method should be carried out according to the regulations in the watt-hour meter manual.
In single-phase circuits with low voltage and low current, the watt-hour meter can be directly connected to the line. If the load current is very large or the voltage is very high, it should be connected to the circuit through the transformer. At this time, the primary side of the current transformer is connected in series with the load, the secondary side is connected in series with the current coil of the watt-hour meter, the primary side of the voltage transformer is connected in parallel with the load, and the secondary side is connected in parallel with the voltage coil of the watt-hour meter.
How to use a single-phase watt-hour meter
1. Reasonable selection of watt-hour meter: First, select single-phase or three-phase watt-hour meter according to the task. For a three-phase watt-hour meter, it should be selected according to whether the line under test is a three-phase three-wire system or a three-phase four-wire system. The second is the selection of rated voltage and current, and the load voltage and current must be equal to or less than its rated value.
2. Install the watt-hour meter: The watt-hour meter is usually installed with the power distribution device, and the watt-hour meter should be installed below the power distribution device, and its center is 1.5 to 1.8 meters away from the ground. When installing multiple watt-hour meters side by side, the distance between the two meters shall not be less than 200 mm. Meters should be installed separately for power lines with different electricity prices. Electricity lines with the same electricity price should be combined with meters. When installing the watt-hour meter, the meter body must be perpendicular to the ground, otherwise its accuracy will be affected.
3. Correct wiring: According to the requirements of the manual and the wiring diagram, the incoming and outgoing wires should be connected to the outlet of the watt-hour meter in turn. When wiring, pay attention to the phase sequence relationship of the power supply, especially the reactive watt-hour meter, and pay attention to the phase sequence.
