Three-phase meter - a device for measuring electricity consumption in an alternating current network with a voltage of 380 V. Single-phase meters are used in 220 V networks in office and residential premises. Devices operating in a three-phase network are installed in large industrial enterprises. With the use of powerful electrical equipment, they are increasingly used in the electrical lines of private and country houses.
Content
- Types of devices
- Design features and principle of operation
- Popular models
- Connection diagram
Types of devices
Three-phase electricity meters are divided according to the type of connection and measured values, types of designs. By the way they are connected to the electrical network, they are divided into 2 types. These include:
- Direct connection - devices are installed directly in a 220 or 380 V network. They have the ability to transmit power up to 60 kW and a maximum current of up to 100 A. Connection is carried out with wires with a cross section of 1.5 to 2.5 mm².
- Indirect connection - meters are connected via transformers and are used in high voltage networks. They are most often used in large production areas.
Structurally, devices are induction and electronic. In induction devices, counting occurs due to the rotation of a conductive disk under the influence of a magnetic field from the coils.
Such units are also called electromechanical. The number of revolutions of the disc is directly proportional to the amount of consumed electrical energy. These counters there are a number of disadvantages:
- lack of remote reading;
- large error;
- one tariff;
- the possibility of using unaccounted electricity.
Increasingly, they are being replaced by electronic devices in which voltage acts on solid-state elements that convert analog signals into pulses.
The advantages of electronic meters include: multi-tariff, remote reading, long service life, high measurement accuracy.
Design features and principle of operation
A three-phase device differs from a single-phase device in its ability to work in networks where the rated power is 15 kW and above. They are considered multifunctional units, since they can be used both in household networks and to control the operation of three-phase electric motors. The design of the device includes:
-
collapsible body; - two windings: current, voltage;
- aluminum disc;
- magnet to stop the disc;
- worm-gear;
- counting mechanism.
An aluminum disc is located between the two electromagnets. The current magnetic circuit is connected in series, and the voltage electromagnet is connected in parallel. When the meter is turned on, a current flows through the windings, which causes alternating magnetic fluxes.
They penetrate the disc and form inductive eddy currents, which interact with the currents and cause the disc to rotate. Through a worm gear, the counting mechanism periodically rotates.
The main elements of an electronic device are: current and voltage transformers, converter, controller, terminals. The converter receives analog signals from current sensors and converts them into digital pulses.
The pulses are sent to the controller and the display shows figures showing the current energy value.
Three-phase meters are connected to both three-wire circuits and four-wire ones. The devices are capable of storing all information with reference to time.
Popular models
The most popular are multi-tariff three-phase meters. There are many electronic models produced by Russian manufacturers. These include:
-
Mercury 236 ART-02 RS 100 A - the device is designed to account for active and reactive electricity with a direct connection. Has a device for long-term storage of information and its transfer to the collection center. Recording of readings is carried out at 4 tariffs. - Neva 303 1S0 5-100 A - a combined device that can be used both in single-phase and three-phase networks. The display is additionally equipped with an LED indicator.
- Energometer TsE 6803 V / 1 - single rate meter, which is installed on a DIN rail. The maximum amperage for direct connection is 100 A. The products are manufactured by the Stavropol Joint Stock Company.
- Agate 3-1.50.5 - an electronic multi-tariff device with digital indication from Moscow manufacturers. The IRDA communication interface is built into the design. The meter is equipped with protection against common methods of electricity theft. Service life - 32 years.
You can also note the mechanical and electronic models of meters from the Russian companies Matrix, Omron, Kaskad, etc.
Connection diagram
To connect a three-phase meter, an input switch with three or four contacts is required. It is not recommended to use three single-pole circuit breakers, since in them the protective shutdown does not occur simultaneously. Instrument terminals connect from left to right:
- 1 and 2 - input and output of the first phase;
- 3 and 4 - second phase;
- 5 and 6 - connection of the third phase;
- 7 and 8 - points of connection of the neutral wire.
The ground wire is usually routed out through a separate terminal block. Before starting the installation of a new meter, turn off the introductory machine. If the fastening of the old meter does not fit, then new mounting holes are pre-drilled with a drill. Then, using self-tapping screws, the counter is installed on a special platform.
Some models are mounted directly on the DIN rail of the electrical panel. After checking the reliability of the fixture of the device, the wires are connected in series from left to right. After connecting the wires, the machine turns on, and the meter is checked for load.
An appropriate specialist is invited to register and seal the device.
