Rated voltage: definition of the term and types of phase-to-phase parameters of the network and transformers

Every user of electrical appliances came across the concept of rated voltage, who looked at the attached small plate with characteristics. Significant deviations from the established norm will lead to product breakdown. There are standard values ​​of the indicated potentials for various types of networks <1000 volts and more, sources and converters of alternating and direct current.

Types of voltages

One of the energy characteristics of an electric field is a voltage equal to the ratio of the work of charge transfer in joules to its value in coulombs. Other name - potential difference: having 2 points with values ​​of 5 and 10 C, it is possible to determine the interaction between them: 10-5 = 5 J / C, which is 5 V.

The voltage in electrical installations is measured in volts. If its operating value does not exceed 1000, the voltage is considered low. At higher values, the unit of measurement is kV. A voltmeter is used to determine the potential difference. The entire power system is formed from three-phase networks, where

there are 2 types of voltages:

• linear - between two cable cores with potential;
• phase manifests itself when measuring the potential of a wire that is energized and zero - neutral.

When consumers are connected to the network according to the Δ (triangle) scheme, the values ​​of both types of voltages are equal to each other. If the connection is made using Y (star), the numerical value of the linear is √3 times greater than the phase value (1.732). It is customary to write the marking of the voltage measured in a three-phase network in the form of a fraction: 380/660 V, 220/380 V, 127/220 V, where the upper number is phase, the lower is a linear value.

Electrical equipment manufacturers be sure to indicate on the device its main parameters: power in watts, amperage in amperes and rated voltage are the baseline from a standardized series of potentials that determine the insulation level of devices and the network. The table shows the values ​​of the main indicator of the low-voltage power system.

Kind of current	Nominal voltage Unom of power grids and electrical receivers	U nom for generators and converters
~ 1ph	6, 12, 27, 40, 60, 110, 220	6, 12, 28, 42, 62, 115, 230
The same, 3ph	40, 60, 220, 380, 660	42, 62, 230, 400, 690
CONST	6, 12, 27, 48, 60, 110, 220, 440	6, 12, 28, 48, 62, 115, 230, 460

Unom for lines and power grids is the same as for electrical receivers. Voltage suppliers are generators of power plants, converters are secondary windings of transformers.

Household network potential ratings

Exceeding or decreasing the established standard in the power system leads to improper operation of consumers, breakdown of devices. It is especially important to maintain the required level of Unom in production schemes - here the consequences are more severe: up to stopping the technological process. Household appliances according to the degree of susceptibility to a change in value from the most resistant to the most sensitive divided into the following groups:

1. Devices with heating elements: heaters, irons and kettles. With excess voltage, excess power goes into heat, protecting the device from damage.
2. Apparatus with an electric drive in the form of an asynchronous motor: fans, air conditioners, refrigerators. A short-term drop will lead to a malfunction of the equipment, but a long-term power failure will cause a breakdown of the motor windings and the need to replace the motor.
3. Electronic devices: TVs, laptops and computers. Any deviation of the supply network from the norm can disable the devices, therefore, protection is provided in their design. In case of short-term violations, the fuse saves, but prolonged overvoltage leads to the loss of an expensive item.
4. Lighting devices: fluorescent, incandescent, LED lamps. Energy-saving models are more demanding on the constancy of network parameters.

Main characteristics

Voltage stabilizers are used to protect critical electrical circuits from surprises. Depending on the power, they are used in everyday life and in production. The nominal values ​​of the potential for some objects are given in the table.

Construct name	The nature of the current load	Unom in volts, unless otherwise noted
Cardiogram	Pulse	1.0―2.0 mV
Battery: -mizinechikovy, alkaline cell	CONST	1,5
- Crohn's type	9,0
Antenna for TV	High frequency	1―100.0 mV
Laptop rectifier, car battery	CONST	12,0
Phone line	―″―	60
Electric discharge: -step	―″―	250
eel	650
Trolley system of tram, trolleybus	―″―	660
Subway contact rail	―″―	825
Power grid: -Russian Federation	~ variable	220/380
-U.S.A	110/190
-Japan	100/172
Electrified railway	―″―	25 kV
Also	Constant	3 kV
Thunder cloud	―″―	≥10 gigavolts (1 billion volts)

Standard range of nominal values ​​of the network ≥1000 V: 3.0; 6,0; 10,0; 20,0; 35.0... A significant excess of the standard is called overvoltage.

Designated transformer voltage

Transformare - transform, transform. This is an electrical device with two or more windings on a magnetic circuit, designed to transform current or voltage without changing the frequency. A distinction is made between the following definitions of potentials in a converter devicecalled a transformer:

• rated primary voltage - winding 1 is designed for it;
• Unom secondary - potential at the clamps of the sheath 2, measured at idle speed of the converter and the standard value at the input terminals;
• higher U nom of the transformer - the highest of the given winding voltages;
• the lowest nominal potential, respectively, the smaller of the indicators;
• average Unom - intermediate between the two previous values.

During operation, a short-circuit (SC) mode sometimes occurs, when one of the transformer windings is internally connected, and the second remains energized. If an event occurs during operation at rated voltage, short-circuit currents appear in the windings, 5-10 times higher than standard ones. The phenomenon is accompanied by a significant increase in the temperature of the windings, large mechanical loads act in them - the situation becomes emergency.

To prevent such circumstances, they use protection that is triggered in a fraction of a second. The rated line voltages (kV) of high voltage transformers are given in the table.

First winding	3,00; 3,15	6,00; 6,30	10,00; 10,50	20, 0; 21,0	35,0; 36,5	110; 115	158: 165	220; 230	330	500
Second wrapping	3,15; 3,3	6,30; 6,60	10,50; 11,00	21,0; 22,0	38,5	115; 121	158: 165	230; 242	330	―

In order to reduce losses in power transmission lines, the secondary windings have Urated 5 - 10% higher than in the corresponding lines. The exception is short-haul networks, for which the nominal voltage values ​​are set to be the same for the supply and consuming equipment.