Modular Contactors

What is a modular contactor?

Upon receiving an electrical signal, a circuit can be opened or closed by a modular contactor in the electrical panel. Their role is therefore to open or close a circuit, like a switch. They control the operation of electrical circuits, including lighting, heaters, fans, and motors. Contactors are not designed to protect electrical circuits, but to open or close them. In the residential sector, we mainly find day/night contactors, also known as "peak/off-peak" contactors. The primary application of contactors in industry is to start motors (machine tools, furnaces, hoists, etc.).

What's the difference between a relay and a contactor?

Relays and contactors are both electrical switching devices, controlled by a coil and used to open and close an electrical circuit. But that's where the similarity ends, as their uses are quite different. Relays are designed to detect, transmit, convert or eliminate an electrical signal, whereas contactors are there to connect and disconnect the main circuit. Due to its limited contact capacity, relays are only suitable for circuits with low currents, around 5 A. In contrast, contactors are used in industrial applications, facilitating the connection and disconnection of high-power loads with currents reaching 1000 A.

What's the difference between a contactor and an auxiliary contact block?

In simple terms, a contactor is designed to withstand an electric arc generated by a high current when a circuit is opened or closed. They are used to power and control high-power industrial motors. The auxiliary contact block has no power contacts. It is part of the control circuit of an electrical assembly, and can therefore only cut low-value currents. It is intended for switching weak signals and relaying power contactors.

Contactors or modular contactors, which to choose?

In the electrical industry, the term "modular" refers to any LV device installed on a DIN rail inside a switchboard or enclosure. The term "modular" refers to the place of the module in the switchboard, and the width of a module is standardised at 17.5 mm. So a contactor can be a modular contactor when it is installed on a DIN rail. In reverse, a modular contactor can be a contactor.

Different modular contactors

Depending on their use, there are several types of modular contactors. Make the right choice by selecting the number of poles and type of contacts required for each specific function.

The number of poles in a modular contactor

Modular contactors can have 1, 2, 3 or 4 poles. In other words, they have from 1 to 4 power contacts. Single-pole contactors are rarely used and are generally installed within older electrical installations with a common neutral, such as heating systems.

Contact type

Typically, there are two types of contact:

• NO (Normally Open Contacts), sometimes referred to as A contacts
• NC (Normally Closed), sometimes referred to as B contacts

Modular contactor functions

There are 4 main families of modular contactors:

• Domestic contactors for peak/off-peak hours, or for switching on a heating circuit via a centralised thermostat;
• Contactors and motor control contactors. With a particularly long contact life due to a high number of switching operations;
• Reversing contactors. By combining 2 standard modular contactors and a mechanical interlock unit, we can create a reversing contactor that reverses the power supply circuit and, therefore, the motor's direction of rotation. They are mainly used in hoisting applications, for example;
• Safety contactors. These contactors, easily recognisable by their bright colour (red or yellow), use mirrored contacts to indicate the open or closed position of the power poles. They are used, for example, for emergency machine shutdowns.