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A relay Electromechanical relay principle Electromechanical relay schematic showing a control coil, four pairs of normally open and one pair of normally closed contacts An automotive-style miniature relay with the dust cover taken off. A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple ...
A solid state relay (SSR) is an electronic switching device that switches on or off when an external voltage (AC or DC) is applied across its control terminals. They serve the same function as an electromechanical relay , but solid-state electronics contain no moving parts and have a longer operational lifetime.
In electrical systems, a static relay is a type of relay, an electrically operated switch, that has no moving parts. [1] Static relays are contrasted with electromechanical relays, which use moving parts to create a switching action. Both types of relay control electrical circuits through a switch that is open or closed depending upon an ...
A common design principle of these devices is a special galvanic isolation module between the input (control) and the output (switching) circuits of the relay. Interface relays are widely used in control and protection systems of high voltage (10-100 kV) electronic and electrophysical equipment and in high power installations. [3] [5] [6]
In many cases, it is possible to design a relay logic diagram directly from the narrative description of a control event sequence. In general, the following suggestions apply to designing a relay logic diagram: 1. Define the process to be controlled. 2. Draw a sketch of the operation process. Make sure all the components of the system are ...
A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) [a] is an electrical safety device, more specifically a form of Earth-leakage circuit breaker, that interrupts an electrical circuit when the current passing through line and neutral conductors of a circuit is not equal (the term residual relating to the imbalance), therefore ...
The operating time of relay decreases with the increases in the current. The operation of the relay depends on the magnitude of the current. [33] An inverse definite minimum time (IDMT) relay is a protective relay which is developed to overcome the shortcomings of the definite time overcurrent (DTOC) relays. [1]: pp 30-31 [34]: 134
After the control of air flow and temperature was standardized, the use of electromechanical relays in ladder logic to switch dampers became standardized. Eventually, the relays became electronic switches, as transistors eventually could handle greater current loads. By 1985, pneumatic controls could no longer compete with this new technology ...