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AC contactor for pump application. A contactor is an electrically controlled switch used for switching an electrical power circuit. [1] A contactor is typically controlled by a circuit which has a much lower power level than the switched circuit, such as a 24-volt coil electromagnet controlling a 230-volt motor switch.
For contact spots of radii smaller than the mean free path of electrons , ballistic conduction of electrons occurs, resulting in a phenomenon known also as Sharvin resistance. [10] Contact force or pressure increases the size of the a-spot which decreases the constriction resistance and the electrical contact resistance. [11]
The current rating of smaller NEMA contactors or their auxiliaries are defined by NEMA ICS 5: Industrial Control and Systems, Control Circuit and Pilot Devices [1] standard. The nomenclature is a letter followed by a three-digit number, the letter designates the current rating of the contacts and the current type (i.e., AC or DC) and the number ...
Vacuum interrupter with ceramic housing. In electrical engineering, a vacuum interrupter is a switch which uses electrical contacts in a vacuum. It is the core component of medium-voltage circuit-breakers, generator circuit-breakers, and high-voltage circuit-breakers.
Continuous current ratings for common contactors range from 10 amps to several hundred amps. High-current contacts are made with alloys containing silver. The unavoidable arcing causes the contacts to oxidize; however, silver oxide is still a good conductor. [22] Contactors with overload protection devices are often used to start motors. [23]
Arc suppression is an area of interest in engineering due to the destructive effects of the electrical arc to electromechanical power switches, relays and contactors' points of contact. [11] There are many forms of "arc suppression" that provide contact protection in applications operating at less than 1 Ampere .
The development of the varistor, in form of a new type of rectifier based on a cuprous oxide (Cu 2 O) layer on copper, originated in the work by L.O. Grondahl and P.H. Geiger in 1927. [3] The copper-oxide varistor exhibited a varying resistance in dependence on the polarity and magnitude of applied voltage. [4]
Plasma contactors are devices used on spacecraft in order to prevent accumulation of electrostatic charge through the expulsion of plasma (often Xenon). An electrical contactor is an electrically controlled switch which closes a power or high voltage electrical circuit .