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The redundant design ensures that wiring errors do not lead to the loss of the safety function. Two relays (K1, K2) with positive-guided contacts provide the safe switching contacts. The two input circuits CH1 and CH2 each activate one of the two internal relays. The circuit is activated via the start relay K3.
Since relays are switches, the terminology applied to switches is also applied to relays; a relay switches one or more poles, each of whose contacts can be thrown by energizing the coil. Normally open (NO) contacts connect the circuit when the relay is activated; the circuit is disconnected when the relay is inactive.
Digital relays can also provide functions such as communications interface, monitoring of contact inputs, metering, waveform analysis, and other useful features. Digital relays can, for example, store multiple sets of protection parameters, [27] which allows the behavior of the relay to be changed during maintenance of attached equipment ...
High voltage interface relays, a.k.a., interface relays: [1] [2] or coupling relays or insulating interfaces [3] [4] is a special class of electrical relays designed to provide informational and electrical compatibility between functional components isolated from each other and not allowing for a direct connection due to a high difference of potentials.
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.
Today, microprocessor-based relays can perform many protective functions in one device. [1] When one device performs several protective functions, it is typically denoted "11" by the standard as a "Multifunction Device", but ANSI Device Numbers are still used in documentation like single-line diagrams or schematics to indicate which specific ...
The National Association of Relay Manufacturers and its successor, the Relay and Switch Industry Association define 23 distinct forms of electrical contact found in relays and switches. [ 12 ] A normally closed ( NC ) contact pair is closed (in a conductive state) when it, or the device operating it, is in a deenergized state or relaxed state.
At least two separate faults would be required to allow this relay to close inadvertently. Double switching, double cutting, or double breaking is the practice of using a multipole switch to close or open both the positive and negative sides of a DC electrical circuit, or both the hot and neutral sides of an AC circuit.