Contactor

What is a contactor?

A contactor is an electrically regulated switch used for switching an electrical power circuit. A circuit generally controls it with a much low power level than the switched circuit, such as a 24-voltage coil electromagnet controlling a 230-voltage motor switch.

Unlike relays, contactors are directly connected to high-current load electrical devices. Devices exchanging more than 15 amperes or circuits rated more than a few kilowatts are called contactors. Apart from that optional auxiliary low current contacts, contactors are almost solely fitted with normally open (“form A”) contacts. They are designed with features to control and subdue the arc made when interrupting heavy motor currents.

Components of Contactors:-

• The contacts are the current-moving part of the contactor. This contains power contacts, auxiliary contacts, and contact springs. 
• The electromagnet (or “coil”) delivers the driving force to shut the contacts.
• The enclosure is a structure housing the contacts and the electromagnet. Enclosures are created of insulating materials such as Bakelite, Nylon 6, and thermosetting plastics to shield and insulate the contacts and provide protection against personnel touching the contacts.

Applications

Lighting control

Contactors provide central control of large lighting installations, such as office buildings or retail buildings. Latching contactors reduce power consumption in the contactor coils, which have two operating coils. The first coil, momentarily energized, closes the power circuit contacts, which are then mechanically held closed; the second coil opens the contacts.

Magnetic starter

A magnetic starter is a device created to supply power to electric motors. It includes a contactor as a vital component while providing power-cutoff, under-voltage, and overload safety. 

Vacuum contactor

Vacuum contactors are only functional for use in AC systems. The AC arc generated upon opening the contacts will self-destroy at the zero-crossing of the existing waveform, with the vacuum controlling a re-strike of the arc across the open contacts. Vacuum contactors are, thus, very efficient at disrupting the energy of an electric arc. They use when relatively fast switching is required, as the periodicity of the AC waveform determines the maximum break time.

Mercury relay

A mercury relay sometimes called a mercury displacement relay, or mercury contactor, is a relay that uses the liquid metal mercury in an insulated sealed container as the switching component.

How Long a Contactor Stands - The Life Longing of a Contactor

The life longing of a contactor or its “contact life” is one of the most important concerns of a user. So naturally, the contacts are being opened and closed more repeatedly, and the life of the contactor will reduce. This is because the opening and closing of the contacts form an electric arc, which generates extra heat. The continuous production of these arcs can damage the contact surface.

Likewise, the electrical arcs cause pitting and burn marks, eventually blackening the contactors. However, the black deposit or oxide on the contactors makes them more capable of efficiently conducting electricity. However, they must be replaced when the contactors get worn out and eroded to a large extent.

Therefore, the faster the contact closes, the quicker the arc destroys. This, in turn, enables to enhance the life of the contactor. The latest contactor versions are created so that they close very quickly and vigorously. Which causes them to slam against each other and generate a bouncing action as they rebound. This action is known as contactor bounce. The contactor bounce phenomenon forms a secondary arc. Therefore, it is not only essential to close the contactor fast but also to reduce the contactor bouncing. This helps reduce wear and secondary arcing.

BCH Contactor is ideal for tough industrial applications. When using BCH Contactor and overload relays, you choose reliability to lower maintenance time and increase productivity. BCH offers a wide range of contactors to control single or multiple capacitor banks efficiently.