Auxiliary contacts

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Auxiliary contacts

Auxiliary contacts belong to the basic electrical apparatus. They are often referred to as auxiliary contactors. They are switching apparatus, used in control circuits and auxiliary circuits.

Auxiliary contacts: characteristics

Auxiliary contacts are used to implement control systems, signaling or electrical interlocks. Their role is to transmit information about the operation of a particular receiver. Therefore, such an electrical switch must be very well adapted to the tasks to be performed. Front auxiliary contactors are mounted on the front of the main unit. Auxiliary contacts, made of durable materials, guarantee the safe use of the indicated device. This type of component is designed to work for both alternating and direct voltages. Auxiliary contacts can be equipped with screw terminals or spring terminals. The basic models have 4 poles, although, when justified, this number can be increased to 8 by means of an auxiliary contact block.

The main difference between auxiliary contacts and contactors is that contactors connect high-current systems, while relays connect only those devices that transmit low-current or zero potential signals. The contactors are used to connect electrical devices, such as motors, and the auxiliary contacts are used to provide control signals, such as from or to PLCs. However, both contactors and auxiliary contacts work on the same principle. They pass on a signal by means of a junction. Depending on how a particular device is constructed, the signal may be voltage or current.

Contactor as an electrical switch, whose contacts are in the open state, and their change to closed when another device or electromagnet operates is responsible for on and off specific systems. It is worth noting that contactors can perform a function such as conducting current under all conditions. Not only when the circuit operates normally, but also when there are overloads. Contactors are used in: heaters, fans, pumps, sirens, lamps, and motor circuits. Each contactor consists of a coil, operating contacts and auxiliary contacts. There can be several auxiliary contacts in a contactor. The most commonly used are the front auxiliary contacts, whose role is to provide information about the operation of a particular load. Front auxiliary contacts for contactors are mounted on the front of the contactor. They are made of durable materials, ensuring the safe use of the entire device. This ensures that the main circuits remain intact.

Auxiliary contacts: use in contactors

Auxiliary contacts have the same role as relay contacts. Therefore, they are used to transmit information. They can be NO or NC contacts. They switch on (NO) or off (NC) as soon as the coil is energized. Auxiliary contacts

In contactors, auxiliary contacts are mainly used for:

  • transmit a message about the operation of a designated load, for example to a PLC or by lighting an indicator lamp,

  • blocking the activation of another contactor,

  • self-sustaining contactor,

  • logic for controlling contactors by so-called cascade control.

Auxiliary contacts are used in large numbers, for indirect control of motors, valves, couplings and heating equipment. Due to the use of appropriate design, galvanic separation is ensured between the control circuit and the switched circuit, and in the off state between the input and output of the contacts. The main advantages of these components are: simple design, uncomplicated control structure, easy start-up, high level of safety. Auxiliary contacts are ideal for modular use. Therefore it is good to use them where their application is justified.