Relay. Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Relay. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Electrician's Handbook

Relay - this is a device for automatic switching of electrical circuits by a signal from the outside (English Relay - change, relay race, road station where horses were replaced; French relais, from relay - change, replace).

Composition

Any relay device, like a relay for switching electrical circuits, consists of two main parts:

relay element (with two states of stable equilibrium);
groups of electrical contacts that close (or open) when the state of the relay element changes.

Classification

On method of connection to the main electrical circuit protection relays are divided into:

primary, connected directly to the main electrical circuit;
secondary, connected via inductive or capacitive coupling.

On the method of influencing the disconnecting electrical installation relay devices are divided into two groups:

relay of direct action (directly affect the disconnecting device);
relay of indirect action (act through an intermediate element).

On purpose of relays are divided into two groups:

measuring, designed to operate with a certain accuracy at a predetermined value of the influencing quantity within the continuous range of its change;
logical, designed to operate or return with a discrete change in the influencing value.

Measuring relays, designed to operate at values of the influencing quantity greater than the specified one, are called maximum relays, with values of the influencing quantity less than the specified one, - minimum relay.

On type of influencing quantity measuring relays are divided into the following groups:

current relay (influencing value - current);
voltage relay (influencing value - voltage);
power relay (influencing value - the product of current, voltage and the sinusoidal function of the angle between them);
phase shift relay (influencing quantity - angle between input vector quantities);
power direction relay (influencing value - the angle between the input vector quantities of current and voltage);
resistance relay (influencing value - the ratio of voltage to current, expressed in complex form);
relay of symmetrical components (influencing value - symmetrical components of current and voltage or their combination);
frequency relay (influencing value - frequency of alternating current).

A measuring relay that performs the functions of several relays united by a logical connection is called combined.

In addition to measuring relays in protection devices, logic relays. These relays are:

intermediate relays designed to expand the functions of other relays;
indicator relays designed to indicate the operation of other relays;
time relays designed to operate with an adjustable time delay having a given accuracy;
delayed relay designed to trip or reset with a specially designed delay.

According to the principle of operation of the protection relay are divided into the following groups:

electromagnetic relays (the work is based on the effect of the magnetic field of the current flowed around the winding on the ferromagnetic armature);
polarized relays (electromagnetic relay with an auxiliary polarizing magnetic field);
magnetoelectric relays (work is based on the interaction of a permanent magnet and a current-blown relay winding);
induction relays (work is based on the interaction of magnetic fields of fixed windings with magnetic fields of currents induced in a moving element);
semiconductor relays (the work is based on the use of the properties of semiconductor devices).

Author: Koryakin-Chernyak S.L.

See other articles Section Electrician's Handbook.

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