# What is an electricity meter? The working principle and classification of electricity meters are introduced

Electricity meter is used to measure electric energy meter, also known as electricity meter, fire meter, kilowatt-hour meter, refers to the measurement of various electric quantity meters.

When using an electricity meter, it should be noted that at low voltage (not more than 500 volts) and small current (tens of amps), the electricity meter can be directly connected to the circuit for measurement. In the case of high voltage or high current, the watt-hour meter cannot be directly connected to the line. It should be used with the voltage transformer or current transformer.

How an electricity meter works

When the watt-hour meter is connected to the circuit under test, alternating current flows through the current coil and the voltage coil, and these two alternating currents produce alternating flux in their iron cores respectively. Alternating magnetic flux passes through the aluminum disk and induces eddy currents in the aluminum disk; ​the eddy currents in the magnetic field under the action of force, so that the aluminum disc to obtain a torque (active moment) and rotation. The greater the power consumed by the load, the greater the current through the current coil, the greater the eddy current induced by the aluminum disk, and the greater the rotational torque of the aluminum disk. That is, the torque is proportional to the power consumed by the load. The greater the power, the greater the torque, and the faster the disc rotates. When the aluminum disk rotates, it is subjected to the braking torque produced by the ** magnet. The braking torque is opposite to the active torque. The braking torque is proportional to the speed of the aluminum disc. The faster the aluminum disc rotates, the greater the braking torque is. When the active torque and brake torque reach temporary equilibrium, the aluminum disc will rotate at a constant speed. The electrical energy consumed by the load is proportional to the revolution of the aluminum disk. When the aluminum plate turns, it drives a counter to indicate the electrical energy consumed. This is the simple process of how an electricity meter works. Classification of commonly used electricity meters

(1) Electricity meters can be divided into DC electricity meters and AC electricity meters according to the circuit used. Ac watt-hour meter can be divided into single-phase watt-hour meter, three-phase three-wire watt-hour meter and three-phase four-wire watt-hour meter according to its phase line.

(2) Electricity meter according to its working principle can be divided into electrical mechanical electricity meter and electronic electricity meter (also known as static electricity meter, solid state electricity meter). Electro-mechanical watt-hour meters are used in AC circuits as common electric energy measuring instruments, among which induction watt-hour meters are commonly used. Electronic watt-hour meters can be divided into all-electronic watt-hour meters and electromechanical watt-hour meters.

(3) The electricity meter can be divided into integral electricity meter and split electricity meter according to its structure.

(4) According to its use, electricity meter can be divided into active electricity meter, reactive electricity meter, maximum demand meter, standard electricity meter, multi-rate time-of-time electricity meter, pre-paid electricity meter, loss electricity meter and multi-function electricity meter.

(5) According to its accuracy level, electricity meters can be divided into ordinary installed electricity meters (0.2, 0.5, 1.0, 2.0, 3.0) and portable precision electricity meters (0.01, 0.02, 0.05, 0.1, 0.2).