{"id":80322,"date":"2026-10-22T00:10:00","date_gmt":"2026-10-22T00:10:00","guid":{"rendered":"https:\/\/www.ktb-europe.com\/?p=80322"},"modified":"2026-10-21T21:55:20","modified_gmt":"2026-10-21T21:55:20","slug":"contactor-vs-relay-difference","status":"publish","type":"post","link":"https:\/\/www.ktb-europe.com\/en\/blog\/unterschied-schuetz-relais\/","title":{"rendered":"Contactor vs relay: the difference simply explained"},"content":{"rendered":"

A component has burnt out in the control cabinet of an older packaging machine. The housing shows a coil voltage and, below it, a few contact markings. The colleague from purchasing asks: \u201cSo is this a relay or a contactor? And aren\u2019t they the same thing anyway?\u201d<\/p>\n

It is a fair question. Both components work on the same principle, and both use a coil to switch contacts. Even so, they are not interchangeable. If you fit a relay where a contactor belongs, you risk welded contacts, a motor that no longer switches off, or a fire in the control cabinet.<\/p>\n

This article explains the difference between a contactor and a relay in plain terms: how both work, where they are used, how to recognise them and what you need to specify for a replacement.<\/p>\n

The shared principle<\/h2>\n

Relays and contactors are electromagnetically operated switches. When current flows through a coil, a magnetic field is created. This pulls in a movable armature, and the armature moves the contacts. When the coil voltage drops out, a spring pushes the armature back and the contacts return to their rest position.<\/p>\n

The point of it all: a small control current switches a separate circuit. The control circuit and the switched circuit are galvanically isolated from each other. That way a controller running on 24 V DC can switch a load at 230 V or 400 V without the two circuits being electrically connected.<\/p>\n

What is a relay?<\/h2>\n

A relay is built for small currents. It switches signals and control circuits: an indicator lamp, a controller input, the coil of a contactor or a low-power solenoid valve. Typical relays are compact, often plug into a socket and frequently have changeover contacts, i.e. contacts that switch between two positions.<\/p>\n

Electromechanical relays are covered by the EN 61810 series of standards. For relays in the control circuits of industrial plants, EN 60947-5-1 also applies, with its utilisation categories for control circuits, such as AC-15 for electromagnetic loads on AC and DC-13 for electromagnets on DC.<\/p>\n

What is a contactor?<\/h2>\n

A contactor is built for switching power. It switches motors, heaters, lighting groups or capacitor banks \u2013 in other words, loads with high currents, often three-phase. For this it has three main contacts, usually normally open, plus auxiliary contacts for control and signalling functions.<\/p>\n

The crucial difference lies inside. When high currents are switched off, especially under an inductive load such as a motor, an arc forms. A contactor is designed for this: its main contacts usually break the current at two points at once (double break), and arc chutes extinguish the arc quickly. A relay does not have these features.<\/p>\n

Contactors for motors and other loads are tested to EN 60947-4-1. This standard defines the utilisation categories that indicate what kind of load a contactor is designed for:<\/p>\n