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Modular Contactors Explained — What They Do and When to Use Them

Enclosures & Components

Modular Contactors Explained

A contactor is an electrically operated switch. It carries load current on command from a control signal, which makes it the part that actually connects and disconnects a charger or load.

Quick answer

A modular contactor switches a load on and off from a low-power control signal on its coil. It is not a protective device: it does not protect against overload, short circuit or earth faults, so it is always used alongside MCBs, RCBOs or RCDs.

How it works

A control signal energises the coil, which closes the contacts and connects the load. Remove the signal and the contacts open. That lets a small controller, timer or protection relay switch a large load safely.

Where contactors are used

  • EV charging: switching the supply to the charger on and off under controller or protection-device command
  • PEN fault and PME protection units, which disconnect the charger by opening a contactor when a fault is detected
  • Time-switched or tariff-controlled loads
  • Load shedding and load management

Choosing one

Check Why
Pole count 4-pole for three-phase loads, 2-pole for single-phase
Current rating Must exceed the load current, for example 63A or 100A
Utilisation category Match the type of load switched, as stated on the datasheet
Coil voltage Must match the control supply
AC or DC DC circuits need DC-rated contactors

WCED modular contactors are certified to BS EN IEC 60947-4-1. Always protect the circuit with a suitable MCB or RCBO as well.

Shop contactors and relays

63A and 100A 4-pole modular contactors, plus DC contactors.

Contactors

Frequently asked questions

Is a contactor the same as an MCB?

No. An MCB protects against overload and short circuit. A contactor only switches. You normally need both.

Can a contactor replace an isolator?

Not on its own. An isolator provides a visible or verified isolation point, whereas a contactor is a controlled switch, so follow the regulations for isolation.

Why do EV protection units contain a contactor?

So the unit can disconnect the charger automatically when it detects a fault, such as a PEN fault.

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