Date: 2026-08-19
A contactor is an electromechanical device for remote and automated switching on and off of electrical loads. It is used to control electric motors, pumps, fans, heating systems, lighting and various industrial installations.
The correct selection of a contactor should not be based solely on the rated current. It is necessary to take into account the type of load, the category of use, the voltage of the control coil, the number of power poles and the required auxiliary contacts.
1. Determine the type of cargo
The first step is to determine what equipment the contactor will control. Electric motors, heating loads, and lighting systems have different starting and operating characteristics.
Motors, for example, can generate significant starting current. Therefore, a contactor suitable for a resistive load is not necessarily suitable for controlling a motor with the same rated current.
2. Check the operating current and power
The rated operating current of the contactor must be in accordance with the current of the controlled load and the applicable utilization category. When controlling an electric motor, the data on the motor nameplate and the technical documentation of the contactor must be checked.
The power in kW can serve as a guideline, but the final choice must take into account the operating voltage, rated current, operating mode and switching frequency.
3. Choose the correct coil voltage
The control coil operates the contactor. Its rated voltage must match the voltage in the control circuit.
Contactors are available with a variety of coil voltages, including AC and DC options. An incorrectly selected coil may prevent normal operation or cause damage to the device.
4. Determine the number of poles
The number of main poles is selected according to the electrical diagram and the load being controlled. For three-phase electric motors, three power poles are commonly used, while other applications may require a different configuration.
Before purchasing, it should be checked whether the specific contactor meets the wiring diagram and installation requirements.
5. Check the auxiliary contacts
Auxiliary contacts are used for signaling, latching, interlocking, and interaction with other control devices. They can be normally open — NO, or normally closed — NC.
Check that the selected contactor has the required configuration. If necessary, additional auxiliary contact blocks can be used if the specific series allows it.
6. The contactor does not replace the protection
The contactor is a control device and does not replace a circuit breaker, fuse or overload protection. When controlling an electric motor, it is usually necessary to provide appropriate short-circuit and overload protection.
Protective and control devices must be coordinated according to the load characteristics and the requirements of the electrical installation.
7. Standard or modular contactor
Standard contactors are widely used to control motors and industrial equipment. Modular contactors are designed for installation in distribution boards and are often used in lighting, heating and other building applications.
The choice between the two types depends on the load, operating mode, required switching capacity, installation location and switchboard design.
Summary
Before choosing a contactor, check:
- the type and rated current of the load;
- operating voltage and power;
- the category of use;
- the voltage and type of the control coil;
- the number of power poles;
- the necessary NO and NC auxiliary contacts;
- installation conditions and operating mode;
- the necessary protection against short circuit and overload.
Explore the available E.NEXT contactors and compare the characteristics of individual series and models.
Important: the selection, connection and adjustment of the contactor and protective devices must be carried out by a qualified specialist according to the load, the electrical diagram and the manufacturer's instructions.