Three-phase direct controllers are used to account for consumed electricity. A three-phase meter can be installed in areas with a combined power of more than 12 kW or 60 A, including in residential premises.
The need for three-phase metering
Current standards establish the requirement to use multiphase metering devices for consumers with power from 15 to 20 kW. With this indicator, the current in the circuit reaches 70 A, which is unacceptable for apartments.
PUEs also indicate that the modern power supply system is designed for 380 V, and only a 3-phase device can correctly take it into account. The entire power consumption can be divided into 3 cores, so that each will have about 2.5 A load.
The three-phase system is universal because it ensures the safety of household appliances, reduces the temperature load on the wire and prevents human injuries.
A three-phase type controller in a private house requires significant material investment.
Features of construction and work
To understand the principles of operation of a 3-phase meter in a network with a rated power of 15 kW or more, you should understand its design. A standard apparatus consists of the following parts:
- collapsible housing;
- two windings - voltage and current;
- aluminum disc;
- magnetic disk stop;
- worm-gear;
- counting device.
The principle of operation of the device depends on its type.
Analog models
Electrical energy passes through the current coil, creating an electromagnetic field. Next, eddy current is generated, which ensures the rotation of the aluminum disk. The torsion force is transmitted through the worm gear via a counting mechanism that fixes the consumption of electricity.
The higher the load on the coil, the faster the kilowatts are counted.
Electronic models
The design of the meter has an analog-to-digital converter. From it, pulses arrive at the microcircuit in the frequency graph. The microcircuit of a three-phase electronic meter stores information and displays it on the screen.
Electronic devices often fail due to voltage fluctuations.
Advantages of connecting to 3 phases
By installing a multi-tariff meter, the owners of a house or apartment receive many benefits:
- saving - some models have day and night charging modes, which allows you to use less energy at night than during the day;
- universality - devices can be connected from a standard 220 V network or a new 380 V network directly or through a transformer;
- continuous monitoring - the counter balances the mains voltage;
- accuracy - accounting for the consumed electricity is made with an error of 0.2 to 2.5%;
- additional functions - the counters are equipped with an event log, an electric power modem, user fixation, a monitor for data output.
The single-phase version gives an error of up to 5%.
The specifics of a modern three-phase meter
A multiphase apparatus must be reliable, durable, accurately transmit readings. Therefore, models of modern manufacturers are endowed with functions:
- tracking active and reactive electricity;
- the presence of self-diagnosis;
- taking readings at several rates;
- registration of incidents on line in the journal of notifications.
Some devices are compatible with smartphones, which allows you to track the reading remotely.
Types of electricity meters
Manufacturers produce three types of 3-phase electric meters:
- Direct connection - similarly to single-phase ones, they are connected to a network of 380 or 220 V. The throughput power of the devices is up to 60 kW, the maximum current does not exceed 100 A. For connection, wires with a cross section of 1.5-2, mm2 are suitable.
- Semi-indirect switching - they pop up through a transformer, therefore they are suitable for a network with a large load. Indications are calculated by multiplying the difference between previous and subsequent data by the transformation ratio.
- Indirect inclusion - connection is carried out through voltage and current transformers. They are used to account for electricity during high voltage integration.
The wiring diagram of the device will depend on its type.
Varieties of wiring diagrams
Three phase direct connection meter
The device is designed for installation in power lines with a current strength of up to 100 A. So you can reduce the load of equipment compatible with metering devices up to 60 kW. A feature of direct counters is the impossibility of connecting contacts to conductors of large cross section. Connect as follows:
- 5 mm insulation layer is removed from the cable. Oxidation is removed with a solvent.
- The conductors are connected to a three-pole circuit breaker installed for the meter. This is done in order to protect it from short circuits on the power line.
- There are contacts in the terminal compartment of the device.
- 3 phase wires from the power circuit breaker are thrown on the odd ones.
- Input and output neutrals are connected to terminals No. 7 and No. 8.
- After installing the accounting module, an automatic machine is installed, similar to the introductory product.
- The switch is connected to even terminals.
- The equipment is divided into groups and machines are placed on each phase (for networks with a voltage of 220 V).
Features of the wiring diagram can be found on the terminal board cover.
Semi-indirect metering device connection
The semi-indirect electric meter pops up on metering transformers. It is necessary to calculate the amount of energy used, focusing on the conversion index. To do this, use one of the schemes:
- Ten wire. It will take 11 wires that connect from right to left. On the first 3, phase A is connected, on the second 3 - phase B. Phase C is thrown on cables No. 7-9, on the tenth - neutral. Connect the three-phase to the test pads.
- Star. Application of the circuit allows to reduce the number of conductors. First, at one common point, the first unipolar outputs of the secondary winding are assembled. The next 3 points from the outputs are sent to the counter. Current windings are connected.
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- Star
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- Ten wire
Semi-indirect models are also allowed to be thrown using the coupling of the current circuit with the voltage circuit.
Indirect counter connection method
With minimal energy consumption, an indirect connection is relevant. Since increased current flows through the metering products, a separate transformer is required. The converter breaks the current winding when connected. The scheme is implemented sequentially:
- Selection of materials for the primary and secondary circuits. For the primary, you need a thick conductor passed through the center of the transformer. The secondary is wound from a thin wire.
- Transformers are thrown on each of the phases and are attached to the rear wall of the control cabinet.
- The ends of the wires of the primary are connected to the machine at the input.
- The second part of the primary circuit contacts with individual conductors with a cross section of 1.5 mm2 is connected to terminals No. 2, 5 and 8.
- The secondary coil is connected with similar cables to the terminals of the meter - 1 to 3, 4, and 6 and 7 to 9.
- A neutral wire is thrown on the terminal blocks No. 10 and 11.
If the connection sequence is not followed, the meter will transmit incorrect readings.
The nuances of choosing a counter for 3 phases
A high-quality three-phase energy meter will ensure accurate control of energy costs and save finances. When buying a device, consider:
- The voltage parameters with which the device is compatible are indicated on the housing or in the passport.
- If the installation is carried out outdoors, you must familiarize yourself with the permissible temperature rise.
- The accounting device must have black or red seals on the screw connections. On the electronic device, it is one, on the inductive - two.
- The minimum test period is once every 8-16 years. Less time is indicated by a poor quality counter.
- The presence of a certificate of compliance with domestic GOST and permission to install in the Russian Federation.
- Type of installation. A 3-phase meter for fixing energy costs is mounted on bolts or a DIN rail.
- Term of seals - must be on the meter for no more than 1 year.
- The accuracy class of a high-quality accounting apparatus is at least 2.
- Power indicators. If all the appliances in the apartment in total use no more than 10 kW, a modification of 60 A is suitable. An indicator of 10 kW provides for the installation of a device of 100 A.
- Automated flow control is needed to correctly display information to energy company representatives.
- Availability of tariff plans. Two-tariff models provide a schedule from 7 am to 11 pm and from 11 pm to 7 am. The nightly rate requires spending 50 less electricity.
A new meter can be connected only after sealing by an authorized authority.
Using a three-phase meter as a single-phase
According to the technical guidelines for a network of 15 kW, 3-phase meters can be installed. Network organizations and Energosbyt do not have the authority to indicate the number of connected phases. But this applies only to temporary use for the period of construction work.
Users who decide to include a three-phase as a single-phase, need to know the following:
- after the device, you can put 3 separate machines and throw up a 3-phase cable;
- an input is made to the counter, from which 1 phase goes;
- it is impossible to obtain official permission for such a line, since a 3-phase meter is used only on a three-phase four-wire network;
- on analog models, phases cannot be combined;
- when installing electronic, each phase is checked in turn;
- the load on the network will be asymmetric, which will lead to equipment breakdowns, accidents, injuries.
A three-phase electricity meter in one phase will incorrectly read the readings.
Networks powered by 3 phases provide high-quality connection of a large number of powerful equipment - air conditioners, electric stoves, heaters. Three-phase electric meter allows you to accurately control energy consumption, has several tariffs and the ability to install on the street.
