What is a Contactor? | Type | working | Contactor vs Relay?
A contactor is an electrical device that acts like a switch to turn on and off higher-load electrical equipment. A contactor is an electrical device that is used to control heavy loads like motors, Outdoor units, Compressors etc. It is an Electromechanical relay that is designed to control higher current and voltage as compared to a regular relay or normal relay.
A contractor consists of a coil known as a magnetic coil, a set of contacts and a frame. When a voltage is applied to the contactor coils. It gets energies and the magnetic field is generated, This magnetic pull the Contactor contactor together, which allows to flow current from one end to another through contact, when voltage applied to the coil is stop, then again the contactor coil gets de-energized, and contact return to their initial position.
Contactors are commonly used in small equipment and commercial application like HVAC, Electrical equipment, manufacturing equipment and electrical vehicle.
They are usually controlled by control panels, Programmable logic controllers(PLCs) and automation systems and can be used to turn on and off electrical equipment or multiple loads at once.
Component of Contactor ?
It is an electromechanical device that is used to control the flow of current through contact, by applying voltage between its coil. It is made up of several key components. Which have their importance:-
1. Coil:-
A coil is a part of contactors, that create a magnetic field. That magnetic field pulls its contact together to flow current from one end to another. When Proper voltages are applied to the coil. the coil gets energized. And that creates a magnetic field, which pulls contact together to flow current. The coil is made up of copper wire, which is wrapped in a magnetic core
2. Contacts:-
The contacts are the part of contactors. These are typically NO( means Normally open Contact) and NC ( means Normally Closed Contact).Basically Contacts are two types:-
a) Main Contacts
b) Auxilary contacts
Main contacts are larger contact used to transfer load current whereas auxiliary contacts are used to provide a control signal.
For low application aluminium contact is made but for high load application silver cadmium oxide and silver nickel
3. Frames:-
The frame is an outer cage of contactor, which helps to hold the coil and contact in one place. The frame is designed to protect from the environment and help to hold coil and contact together. The frame is made up of durable materials like plastic, metals etc.
The material used for frame has high arc resistance and welding resistance. These materials must withstand high stress, arc and erosion. The material should be low as low because during a full load of equipment high current is passed through contact.
Working of Contactor?
The whole arrangement is shown in the figure.
An Electromagnetic field is created when the coil gets energized, as we see in the components. The contacts is connected to the armature of the electromagnet.
When gets energized, their electromagnetic field is generated. Then the armature experiences force and pull towards a fixed contact. This is only possible when magnetic force is greater than spring tension force. Now currents start flowing from one end to another end. These contacts remain in contact until the coil de-energizes.
When the coil is de-energized the electromagnetic force becomes zero, due to spring the contact comes back to its initial state and the current flowing from one end to another end is stopped. The contactor is designed in a such way for rapid ON-OFF of load.
The input of the contactor may be AC or DC single phase of 230 Volts or may be AC or DC of 24V. It depends upon the application or need of the user. The universal contactor has a coil that can operate on both AC and DC.
When making and breaking off contact small amount of current is loss due to the arc generated. This is called energy loss of the contactor. While making and breaking contact arc generated, this arc reduces the life of the contactor and also produces harmful gas.
Application:-
It has a wide range of application in various industries.
1) it is used to make starter panels
2) it is used for controlling of current flow from one end to another end for heavy loads like motor,pump, compressors, and havey electric equipments.
3) It is also used in HVAC system for controlling of blower, motor, heaters and compressors.
4) Lighting system:- It is used as commergial and industials scope for controlling of large scale lighting system.
5) Electric Vehicles:- Now a days electric vehicle is increasing, in this industries it is used to controlling power of motors.
6) Elevators and Escalators:- It is used in Elevators and Escalators to control operation of motor. That drives the lifting mechanism.
Difference between Relay and Contactor?
1) Contactors are used for high voltage and current switching application where as relay are used for low current and voltages switching application. If the curren is higher than 15A then Contactor are used, if Current is lower than 15A, relay are used.
2) The size of Contactors are higher as compare to relay.
3) The maintenance of contactor is easy while most of condition relay cannot be repaired.
4) The relay latching time is faster than contactor.
Q & A (Question and Answers)
Q.1) What is Contactor?
A contactor is a electrical device which is used to controlling heavey load like motor, Outdoor unit, Compressor etc.
Q.2) What is Relay?
A relay is an electrical devices, which is used to controlling electrical equipment having low current. Electrical equipment having less than 15A current.
Q.3) What is Contactor coil?
A coil is a parts of contactors, that create magnetic field. That magnetic field pulls its contact together to flow current
Q.4) Difference between contactor and relay?
The function of contactor and relay are same. but main difference is that we can use contactor for heavy load and Relay for Low current Load.
Q.5) How to select contactor?
To select suitable contactor for hour electrical load. Follow below formula:-
Contactor size(A)= 1.5 x Full load Current of LOAD
also we need to check our application or its operating voltage.
Q.6) How to check NO and NC contact?
We can easily check or cross verified NO and NC contact by using a multimeter or continuity tasters. Also, there is a clearly mention about NO and NC on the top of the contactor.
Q.7) Function of contactor?
Contactors are used to Control heavy duty load with singles phase switch or device.
Q.8) Contactor price?
Its price depend on the Make of it. Also depend on the Rating current of contactor.
Q.9) What are the component of contactor?
Components are Coil, Contacts(NO, NC), Frame, Spring, Armature and an electromagnetic coil.
Q.10) Application of contactor?
It is used for the operation of motors, pumps, Electrical panels, compressors, elevators and To make breaker panels.
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