The contactor is an electrical mechanical switch, which is characterized by the fact that it is moved in a way other than manual. This element is designed to switch on, switch off and conduct current in normal operating conditions of the circuit, as well as in case of overloads. These devices allow mechanization of the processes of switching on and off selected electrical devices. This, in turn, improves their lifespan and performance and minimizes the risk of failure and increases safety.

Contactors are used, for example, to switch on:

  • motor circuits,
  • heaters,
  • modular devices,
  • pumps,
  • siren,
  • lamp,
  • fans.

Contactors also give the possibility of connecting accessories that increase functionality (e.g. auxiliary contacts, time releases), and also have a large switching capacity in capacitive and inductive loads and ensure galvanic separation between the contact circuit and the coil circuit.

Contactors vs Relays – what is the difference

A contactor is very similar to an electromagnetic relay in terms of construction and operation. Both work on the same principle – by switching on, they transmit the signal further. The difference, however, lies in the application, because contactors are designed to connect main circuits, and relays - auxiliary ones. Therefore, contactors are called devices for switching on high-current systems, while relays are those that switch on low-current signals or signals with zero potential. Contactors are used to switch devices such as electric motors. Relays, on the other hand, are used, for example, to provide control signals to (or from) PLC (programmable logic controller). In the relay there is a contact gap in one track, while in the contactor there are two switching gaps, which allows it to cope better with disconnecting higher currents and inductive loads. Contactors are usually larger than relays. They have a larger electromagnet and are adapted to withstand higher current overloads, both on the coil and on the contacts. How contactors are built The main elements of a contactor are: working contacts, coil and electromagnet. The device works in such a way that at a sufficiently high voltage on the coil, the contacts remain closed, while when it drops, the armature drops and the contacts are opened by the electromagnet.

The detailed, basic elements of a standard contactor are:

  • insulating base,
  • stationary core,
  • contactor coil,
  • moving armature of the electromagnet,
  • fixed and movable contact,
  • make and break contacts,
  • contact springs ensuring contact pressure,
  • arc extinguishing chambers.

Contactors are distinguished by high mechanical durability with small size and weight. The correct construction, contacts, coils and components of the highest quality are the basis for high mechanical and electrical strength and long service life. Types of contactors

These devices are divided into:

  • AC contactors - they are used to switch on and off various devices. Very often they are used to control the operation of motors, modular devices, pumps, heaters, fans, lamps and sirens;
  • DC contactors - they are used primarily in railway, battery and tram tractions;
  • modular contactors (also called installation contactors) owe their name to their construction, which allows them to be mounted in a modular cabinet on a DIN rail. Modular installation contactors are mounted on modular devices as well as on heaters, pumps and fans;
  • auxiliary contactors - switching devices used in control circuits and auxiliary circuits. The role of auxiliary contacts consists mainly in transmitting information about the operation of a specific receiver).

There are also single-phase and three-phase contactors.

Contactors in the el12 range

The offer of the el12 electrical wholesaler includes all the most popular types of contactors. The products have been grouped into the following subcategories:

  • AC (alternating current) contactors,
  • DC contactors,
  • contactors in modular enclosures,
  • contactor starter kits,
  • contactor parts.

The contactor starter kits subcategory includes, among others: air contactor, direct-on-line starter, star-delta set, reversing starter. Among the parts for contactors, you can find, among others: contact block, auxiliary contacts, coils, auxiliary contact modules, parallel jumper, voltage failure detector, auxiliary-changeover contact, sealing cover for contactor ;w, screw terminal, current limiter, varistor system for contactors, reversing wiring kit, power contactor, star point jumper, phase separation plates, busbar terminal block, thermal overload relay, 4-way joystick body, base mounts for thermal relays, mounting module, overvoltage filter.

How to mount contactors

Contactors, both single-phase and three-phase, are rail mounted. This solution enables precise and quick positioning of the system element in high-current devices. In order for the whole thing to work stably and safely, it is necessary to connect the contactor to the circuit, connect the control, the supporting cable and the cable to switch on the device to the appropriate phase. How to choose the right contactor The choice of contactor is determined by its function and the specified range of system parameters, i.e. the type of current and voltage. In order to select the appropriate contactor for the motor, it is necessary to take into account the value of the rated current consumed by the device in amperes and select a contactor with a nominal current not lower. For example, for an 11 kW motor, a contactor not weaker than 25 A, 11 kW or even more powerful - such as 32 A, 15 kW, will be suitable. For intensive work in industry, oversizing is used, i.e. selecting a contactor 1 or 2 sizes larger. This procedure allows you to extend the life of frequently switched contactors. It is worth remembering that the lifetime of such devices depends on the load category and the number of connections per hour. The time of failure-free operation of a relay or contactor (especially with very frequent on and off cycles) can be effectively extended by appropriate selection and oversizing. In the case of industrial contactors, manufacturers often specify the maximum number of operations that the device can perform in an hour. In the case of modular contactors, this parameter is more often omitted.

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