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Normally closed mercury relay, with coil around top of tube and adjustable angle. A mercury relay (mercury displacement relay, mercury contactor) is a relay that uses mercury as the switching element. They are used as high-current switches or contactors, where contact erosion from constant cycling would be a problem for conventional relay contacts.
Schematic of the Birkeland or Field-Aligned Currents and the ionospheric current systems they connect to, Pedersen and Hall currents. [1]A Birkeland current (also known as field-aligned current, FAC) is a set of electrical currents that flow along geomagnetic field lines connecting the Earth's magnetosphere to the Earth's high latitude ionosphere.
Another type of thermal switch is a PTC (Positive Temperature Coefficient) thermistor; these thermistors have a "cutting off" temperature at which the resistance suddenly rises rapidly, limiting the current through the circuit. When used in conjunction with a thermistor relay, the PTC will switch off an electrical system at a desired temperature.
An inrush current limiter is a component used to limit inrush current to avoid gradual damage to components and avoid blowing fuses or tripping circuit breakers.Negative temperature coefficient (NTC) thermistors and fixed resistors are often used to limit inrush current.
Electromechanical protective relays operate by either magnetic attraction, or magnetic induction. [9]: 14 Unlike switching type electromechanical relays with fixed and usually ill-defined operating voltage thresholds and operating times, protective relays have well-established, selectable, and adjustable time and current (or other operating parameter) operating characteristics.
Leakage current can range from less than a hundred mA at rated voltage up to a few hundred mA at lower voltages. The device can be said to have latching functionality. [6] The hold current is the maximum current at which the device is guaranteed not to trip. The trip current is the current at which the device is guaranteed to trip. [7]
23 – Temperature control device, Heater; 24 – Volts per Hertz Relay (in some old analog applications, a 59 and an 81 device would be chained together as a 59/81 to implement the equivalent of V/Hz protection) 25 – Synchronizing or Synchronism-check Device; 26 – Apparatus Thermal Device, Temperature Switch; 27 – Undervoltage Relay
A Single-Pole, Single-Throw (SPST) mercury switch on millimetre graph paper, device length approximately 1.5 cm Another mercury switch design. A mercury switch is an electrical switch that opens and closes a circuit when a small amount of the liquid metal mercury connects metal electrodes to close the circuit. There are several different basic ...