A three-phase contactor is an electronic device used to turn power on or off at a three-phase load. These devices are used when the voltage requirements of the load exceed the power-handling capability of a mechanical relay. … A contactor uses a low-voltage signal to control the high-voltage circuit.

What is the purpose of a contactor?

A contactor is a special type of relay used for switching an electrical circuit on or off. They are most commonly used with electric motors and lighting applications.

Does a 3 phase contactor need a neutral?

A: Because the supplied three-phase voltage consists of three voltages which are phase-shifted by 120° from each other. Therefore, at any instant in time, current will be returning from the load to the source through at least one phase conductor, without the need of a neutral conductor or a ground conductor.

What does a 3 pole contactor do?

3 pole contactors are electrically controlled switches (relays) used for switching an electrical power circuit. A contactor is typically controlled by a circuit which has a much lower power level than the switched circuit, such as a 24-volt coil electromagnet controlling a 220-volt motor switch.

What is the difference between a contactor and a relay?

A contactor joins 2 poles together, without a common circuit between them, while a relay has a common contact that connects to a neutral position. Additionally, contactors are commonly rated for up to 1000V, while relays are usually rated to only 250V.

How does a single phase contactor work?

When electric current pass through the contactor, it causes the electromagnet to create a strong magnetic field. This magnetic field pulls the armature into the coil, and this creates an electrical arc. Electric currents flow in through one contact and into the device in which the contactor is embedded.

What are two basic types of contactors?

There are different types of contacts in a contactor, and they are; auxiliary contact, power contact, and contact spring. The power contact has two types that are; stationary and movable contact. Material for making contacts must have a high welding resistance and stable arc resistance.

How do you get a 3 phase neutral?

The only way to get a neutral point in a three-phase system is to use a star topology. The only (real) way to convert a delta into a star topology is to use a delta-to-star transformer (AKA Delta-Wye transformer). You often find them at the top of wooden poles.

What are a1 and A2 on a contactor?

One side of the contactor coil (A2) is connected directly to one of the incoming power lines. The other side of the coil (A1) has two possible pathways to complete a connection to the other incoming power line.

Is a contactor coil wired like a load or a switch?

They are wired in circuits exactly like switches and they behave like switches because they are switches. Relay coils are loads; specifically, solenoids.

Article first time published on

What is the difference between starter and contactor?

Here are those: A contactor is an electrically controlled switch similar to a relay. In comparison, a starter is a contactor with the addition of an overload relay. A contactor applies voltage to a contactor coil to close the contacts and to supply and interrupt power to the circuit.

What is difference between contactor and circuit breaker?

The main difference between electrical contactor and circuit breaker is, a contactor is an electrically controlled switch that makes contact to connect the load with the power supply whereas a circuit breaker is an electrical protective device that breaks contacts to disconnect the load from the power supply during a …

How do I choose a contactor size?

1. Type of Contactor = AC7b.
2. Size of Main Contactor = 100%X Full Load Current (Line).
3. Size of Main Contactor = 100%x6 = 6 Amp.
4. Making/Breaking Capacity of Contactor = Value above Chart x Full Load Current (Line).
5. Making/Breaking Capacity of Contactor = 8×6 = 52 Amp.

What are DC contactors?

A DC contactor is an electrically controlled device designed to switch current on and off. DC contactors control current in DC circuits by closing and opening internal contacts. DC contactors control much lower voltages than AC circuits and offer the benefit of minimal arcing as the circuit opens and closes.

What are different types of contactors?

There are two types of power contact; stationary contact and movable contact. The material used for the contacts has stable arc resistance and high welding resistance.

What is the major difference between a contactor and a motor starter?

The contactor applies voltage to a contactor coil to close the contacts and to supply and interrupt power to the circuit. A motor starter is simply a contactor PLUS an overload relay and is rated by motor HP or amperage. If there is no overload relay it is not a starter any longer. It’s back to being just a contactor.

How many terminals does a contactor have?

On the front of the contactor, you’ll see two wire terminals of A1 and A2. This is where we can connect a 24-volt DC power to the coil to energize it. The A1 wire terminal is where the 24-volt DC positive signal wire gets connected and the A2 wire terminal is where the 24-volt DC negative signal wire gets connected.

What are magnetic contactors?

Magnetic contactors are the same as the electrical relays which are used in a number of electric motors. Magnetic contactors are used in the electric motors to balance the change in frequency of the motor or the state of the motor which can be termed as the switching of the motor from ON and OFF state.

Does a contactor need a neutral?

In general, no, a it is not necessary that a lighting circuit, of which a contactor is a part, have a neutral conductor in all cases. The contactor must open all UN-grounded conductors. If the contactor is a single pole, then one of the current carrying conductors must be a groundED (not the groundING) conductor.

What is difference between 220V and 380V?

Two, the difference between the line diameter and the number of turns: relatively, the line diameter of the 220V AC contactor is rough and the number of turns is small; the 380V AC contactor is the opposite, the line diameter is fine and the number of turns is big!

What do the numbers on a contactor mean?

These auxiliary contacts (also called control contacts) each have an order number and a function number. The first number is used consecutively (order number) and the second number specifies the type of contact (function number).

Can a three phase contactor be used for starting a single phase motor?

Yes you can. Feed your single phase in on one pole and then back thru the contactor on the second pole followed by thru the third pole. This will mean that you are going thru the contactor and overload three times which the overload will see as the same effect as a three phase motor being supplied.

How many amps does a contactor coil draw?

The Coil does not draw . 5 amps or 55 watts.

When the contactor coil is de energized?

De-energizing the coil causes it to de-magnetize, releasing the armature and enabling a return spring inside the contactor to snap all three contacts to the open (off) position.

What is 95 and 96 on a contactor?

The contact 95-96 is used to control the load contactor. The overload relays have a setting scale in Amperes, which allows the direct adjusting of the relay without any additional calculation.

What does L and T stand for on a contactor?

With “L” 1,2,3, the L = “Line”, meaning the incoming supply line. For the load side, “L” already had a different meaning, so the the label is T 1,2,3, with “T” = Terminus, meaning the exit point, ie going to the last thing connected in the circuit.

How do you wire a 3 phase contactor?

1. Shut off the power to the three-phase load. …
2. Take additional black, red, and blue three-phase wire that is the same size as the supply wires and connect one end of these wires to the T1, T2, and T3 terminals on the contactor.

Can I use a 3-phase overload for single phase motor?

If you use a 3-phase overload in a single-phase application you will lose protection. This is because the 3-phase overloads needs to see the 3-phase angles and the microprocessor inside the CEP7 overload requires a 3-phase power source to function correctly.

Can a 3-phase switch be used for single phase?

To convert 3-phase to single-phase power, you can use a phase converter. This device can be wired to the motor you plan to run that requires single-phase power. … Then, run two wires from the converter to the power supply.

Does the neutral wire carry voltage?

Voltage is carried by the live conductor, but a neutral conductor is also necessary for two important functions: Serving as a zero voltage reference point. Completing the circuit, providing a return path for the current supplied by the live conductor.

Is neutral the same as ground?

Definitions. Ground or earth in a mains (AC power) electrical wiring system is a conductor that provides a low-impedance path to the earth to prevent hazardous voltages from appearing on equipment (high voltage spikes). … Neutral is a circuit conductor that normally completes the circuit back to the source.