What is contactor
What is contactor?, Contactors are electrically controlled switches, which are controlled by voltage level usually lower than the switched circuit, such as a 48 DC volt coil controlling a 380 AC volt motor
What is contactor designed to control? Contactors are designed to be connected directly to high current electrical loads such as three phase induction motors
Contactor structure
What is contactor structure?
A contactor has three main parts.
- The moving and fixed contacts which are the current-carrying parts of the contactor, This includes both power and auxiliary contacts.
- The coil (or “electromagnet“) provides the driving force which moves and closes the contacts.
- The enclosure is a frame body for the contacts and the coil.
Contactor principle of operation
Magnetic field is produced when current passes through the electromagnet coil, which makes the moving contacts of the contactor to attract.
The force developed by the coil holds the moving contacts and the fixed contacts together.
When the control voltage of the contactor is switched off, a spring returns the core to its normal position and the contacts are opened.
What is contactor used for? Contactors are used to control loads like induction motors and lighting, contactor switch the loads on and off
What is contactor NC and NO?
Contactors have two contacts types:
- Normally open (NO) contacts which allow current in case the contactor control voltage is applied or the contactor is energized
- Normally closed (NC) contacts in the opposite of NO contacts , allow current in case the contactor control voltage is not applied or the contactor is de-energized
What is thermal current rating (Ith) for contactors?
A contactor with 9 Amp. on AC3, And its rated thermal current (Ith = 20 to 25 A) (this means it can switch up to 20 or 25 A for loads of AC1 (thermal load).
N.B: Ith is greater than I of loads with AC3 category
