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Electrical apparatus

Electrical apparatus includes a wide range of products that are used in both low, medium and high voltage electrical installations. Within this category, various methods of grouping can be made, e.g. taking into account the operating voltage, the purpose of the installation, as well as the functions of individual apparatuses and devices.

Electrical apparatus - switches, automatics, power supply, measurement and compensation of reactive power

The tasks of electrical apparatus include, among others. power supply, measurement of electrical parameters, connection and protection, control and compensation of reactive power. Among electrical devices, it is also worth distinguishing modular devices that are widely used both in construction and industry.

Modular apparatus

Modular apparatus includes standardized electrical apparatus and devices. The dimensions of one module are 18 mm wide and 86 mm high. Standardization is aimed at standardizing the devices commonly used in construction and industry, such as overcurrent or residual current circuit breakers. In addition to standardized dimensions, modular devices manufactured by various manufacturers are designed so that they can be mounted on a standard TH 35 rail. The devices can have the width of one module or its multiple (eg 2 or 3). Whenever possible, single-phase devices are single-module, and three-phase - three-module. An example may be the above-mentioned miniature circuit breakers.


The purpose of switches is to connect electrical circuits in a manner appropriate for individual devices. This group of devices includes:

  • disconnectors - cut-off devices, the task of which is to create a safe isolation gap,

  • circuit breakers - devices equipped with extinguishing chambers that enable switching off overcurrents (overload and short-circuit),

  • disconnectors - switches for breaking the operating currents with a maximum intensity equal to the rated current. Disconnectors are not used to disconnect overcurrents.


The task of devices and apparatuses used in automation is to limit human participation in various processes, e.g. production. The most common devices in automatics include:

  • control and measurement devices such as sensors, meters, indicators, recorders or transducers,

  • control devices, e.g. PLC controllers, controllers,

  • input and output modules and communication modules,

  • power supplies.


Electricity supply equipment includes mainly transformers, i.e. electrical machines that use the phenomenon of electromagnetic induction to transfer electricity between circuits, while maintaining frequency. This process is accompanied by a voltage change (except for isolation transformers), which is used to enable the transformation of the power grid voltage from high, through medium to low, and finally supplying end consumers with a relatively safe low voltage.


Electrical measuring equipment includes a number of devices, among which there are frequently used voltage transformers (idle transformers, which enable the extension of the measuring range of voltmeters) and current transformers that allow the use of meters with small measuring ranges for high current measurements.

Even more common devices are the mentioned voltmeters, ammeters, universal meters and meters used to measure the electricity supplied from the power grid, as well as the electricity fed into the grid (e.g. energy produced by photovoltaic cells).

Compensation of reactive power

Losses resulting from an increase in the reactive power factor, both inductive and capacitive, translate into over-contractual reactive power consumption, for which fees are collected. It is assumed that when the annual sum of these fees exceeds the value of approximately PLN 500, it is worth applying compensation that lowers the reactive power factor.

Compensating devices must be properly selected in terms of a number of parameters, and in particular the type of compensated power. The capacitive reactive power is compensated by inductive devices, and the inductive power by capacitive devices. In practice, inductive reactive power is most often compensated by using capacitor banks.