Tungsten Point/Contact

Tungsten:
Tungsten point/contacts are for use in high voltage applications, usually where highly repetitive switching is required. Tungsten has a melting temperature of 3,380oC which gives it excellent arc-erosion resistance.Tungsten may develop troublesome oxide films, especially when used as the anode contact in some DC applications. Therefore, tungsten is often used as the cathode contact, and a palladium alloy used as the anode contact. Such a combination also minimizes contact interface resistance and material transfer.

Copper/Tungsten contact:
A combination of copper and tungsten provides a cost efficient relay contact that resists both arcing and corrosion. However they need to be cleaned or burnished occasionally.

Tungsten-copper contactor is suitable for using the circuit up to the rated voltage 660V AC 50HZ or 60HZ,rated current up to 95A,for making, breaking,frequently starting and controlling the AC motor. Combined with the auxiliary contact block,timer delay and machine interlocking device etc.,it becomes the delay contactor,mechanical interlocking contactor, star-delta starter. With the thermal relay. It is combined into the electromagnetic starter.

Application:

Tungsten point/tungsten contact is widely used in relays.The term Relay generally refers to a device that provides an electrical connection between two or more points in response to the application of a control signal. The most common and widely used type of electrical relay is the electromechanical relay or EMR.

The relay tungsten point/tungsten contact is electrically conductive pieces of metal which touch together completing a circuit and allow the circuit current to flow, just like a switch. When tungsten point/contacts are open the resistance between the contacts is very high in the Mega-Ohms, producing an open circuit condition and no circuit current flows. When the contacts are closed tungsten point/contact resistance should be zero, a short circuit, but this is not always the case. All relay contacts have a certain amount of "contact resistance" when they are closed and this is called the "On-Resistance", similar to FET's. With a new relay and contacts this ON-resistance will be very small, generally less than 0.2Ω's because the tips are new and clean.

Tungsten point or tungsten contact can be made from tungsten rod or tungsten disk.