What is an auxiliary contact on a contactor?

Asked By: Rosend Tomey | Last Updated: 14th February, 2020
Category: technology and computing computer peripherals
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The auxiliary contact is often used in a relay logic circuit, or for some other part of the motor control scheme, typically switching 120 Volt AC power instead of the motor voltage. One contactor may have several auxiliary contacts, either normally-open or normally-closed if required.

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Hereof, what is a auxiliary contactor?

An auxiliary contactor is a regular (low-power) relay - but built like a "power" contactor and when used together with another contactor it is called auxiliary contactor. This is to clarify that it is not used for switching loads but has an activation/deactivation or control function instead.

Secondly, what are the two basic types of contactors? There are different types of contacts in a contactor namely, contact springs, auxiliary contacts, and power contacts. Each type of contact has an individual role to play. Operating Principle of a Contactor: The current passing through the contactor excites the electromagnet.

Beside this, what is an auxiliary contact on a breaker?

Auxiliary contacts are electrically isolated from the main contacts and the protection portion of the breaker. They are usually used to provide a signal to outside equipment that the monitored breaker has tripped for some reason, and to sound an alarm, initiate a safe shutdown, engage a backup power source, etc.

What is the function of auxiliary relay?

auxiliary relay. Relay that operates in response to the opening or closing of its operating circuit to assist another relay or device in performing a function.

39 Related Question Answers Found

What is auxiliary circuit?

An auxiliary circuit is a single-pole, double-throw circuit operated by the movable contact arm assembly. It is used to remotely indicate the position of the main circuit breaker contacts, whether open or closed. Auxiliary switches can be used to operate indicator lights, relays or other accessories.

What is the difference between load and auxiliary contacts?

Explain the difference between auxiliary contacts and load contacts. Auxiliary contacts are small for control circuits. Load contacts are large for large amounts of current. The control side of the relay is separated from the load side by a light beam.

What are the two types of relays?

The two most popular types of these relays include differential and bridge type relays. In differential magnetic system, the difference of two fluxes of permanent magnet acts on the armature.

What are the parts of contactor?

A contactor has three components. The contacts are the current-carrying part of the contactor. This includes power contacts, auxiliary contacts, and contact springs. The electromagnet (or "coil") provides the driving force to close the contacts.

How does a trip coil work?


On medium voltage circuit breakers used on 4 kV up to 35.2 kV , the trip coil is energized by the action of a set of relays (one for each phase, one for ground faults, etc.) that sense some form of fault current flow through the circuit breaker. This done by the action of a reclosing relay.

What is the symbol for a circuit breaker?

225 A/3P Indicates the fixed circuit breaker represented by the symbol as a 225 ampere, three-pole breaker. Indicates that the transformer represented by the symbol is connected delta-wye.

What is an auxiliary contact block?

The auxiliary contact blocks are used for the operation of auxiliary circuits and control circuits for standard industrial environments. The auxiliary contact blocks are equipped with screw type connecting terminals delivered open, protected against accidental direct contact and bear the corresponding function marking.

What is difference between relay and contactor?

Contactors and Relays perform the same task of switching a circuit. Both are electromagnetic switches and operate under similar principles. The difference comes if we see from the application perspective. Contactors are used for high voltage switching purposes whereas relays are used for low voltage switching.

How does a relay trip a breaker?

In a typical application, the over current relay is connected to a current transformer and calibrated to operate at or above a specific current level. When the relay operates, one or more contacts will operate and energize to trip a circuit breaker.

What is a trip coil in circuit breakers?


Such breakers have two electromagnetic coils inside: one to close the breaker contacts and one to open them. The “tripcoil can be energized by one or more protective relays, as well as by hand switches, connected to switch 125 Volt DC power.

What is closing coil in ACB?

Command Close coil is used to switch ON the Power Circuit Breaker remotely. When commanded it releases the spring charged mechanism thus ensuring a rapid connection of the main contacts. Additional connections allow it to be wired out through the trip unit to be commanded through the communications bus.

What is a 52 relay?

48 - Incomplete-Sequence Relay. 49 - Machine or Transformer Thermal Relay. 50 - Instantaneous Overcurrent. 51 - AC Inverse Time Overcurrent Relay. 52 - AC Circuit Breaker.

How does a circuit breaker work?

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current from an overload or short circuit. Its basic function is to interrupt current flow after a fault is detected.

What is an overload relay?

An overload relay is an electrical device used to protect an electric motor from overheating. So it is essential to have sufficient motor protection. For instance, an overload relay can explore without the tripping of a CB (circuit breaker).

What is a definite purpose contactor?


Specifically designed for the HVACR industry, definite purpose (DP) contactors are electrically operated switching devices. They are used for switching a power or control circuit, and are typically controlled by automatic (thermostat) control or manual (pushbutton) interfaces.

What is NO and NC In Contactor?

NO is normally open i.e. the contacts are normally open and close when the switch is actuated. NC is normally closed i.e. the contacts are normally closed and open when the switch is actuated. 1NO1NC is generally used to describe contactors (industrial power relays) and manual switches like emergency stop buttons.

How do you wire a 3 phase contactor?

How to Wire a Three-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.
  3. Connect the control circuit to the positive and negative control terminals of the contactor.