What is a power contactor?
A power contactor or switching contactor is an electromechanical switch. This works like a relay, but contactors are particularly suitable for switching high power. It is internally divided into two circuits, the control circuit and the load circuit. Now, when current flows through the control circuit, the contactor closes the load circuit. Contactors operate in two switching states, open or closed, and switch monostable. This means that as long as the control circuit is energized, the connection state of the load circuit remains unchanged. During monostabilization, the power contactor is prevented from going to the de-energized rest position. Power contactors are used wherever high loads are switched, such as the control of three-phase motors or the switching of strip lights in hall lighting.
How are contactors used?
Contactors and relays are both electromagnetic switches and have very similar structures. They all consist of a coil with an iron core, a moving armature, and one or more contacts. A contactor has contacts that act as switches, and a relay also has contacts that act as changeover contacts. Both consist of galvanically separated control circuit and main circuit. This allows switching operations to be carried out via control lines with a small wire cross-section. The contactor has double switching contacts, actuated by a mechanically robust tie rod, and is thus suitable for high switching capacities at AC voltage.
Difference between contactors and relays
The functions of load switches and disconnectors are combined in the high quality load break switches. Load switches are switches that can only be used in the low and medium voltage range. Among other things, this includes the simple switching on and off of light. Load break switches are usually operated manually. Motors cannot be switched because the inrush current is too high. Circuit breakers, on the other hand, are high-voltage switches. As the name implies, a circuit breaker achieves significantly more power than a switch disconnector. They are also capable of switching on higher currents in the event of a fault, stopping them for a certain time and then switching them off again safely. These include high overload currents as well as short-circuit currents. The biggest difference, then, is the amount of current that a switch-disconnector and a circuit breaker can easily switch. Furthermore, unlike the load-break switch, the circuit-breaker uses an electric drive in addition to the manual drive.