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. … Magnetic contactors act as a safeguard to protect the power supply and the motor.
What is the use of magnetic contactor?
Magnetic contactors are a form of electrical relay found on most electrically powered motors. They act as a go-between for direct power sources, and high-load electrical motors in order to homogenize or balance out changes in electrical frequency which may come from a power supply as well as to act as a safeguard.
What is the main function of contactor?
Function of contactor, generally used for connected and disconnected of electric current supply. Usually in use for applications: motors, heater, lighting or electric power distribution.
How do you test a magnetic contactor?
Turn the control switch on to energize the coil in the contactor. You should hear a clear clicking and humming sound. Other magnetic contactors have a visual hint once the coil is energized. Get the volt ohmmeter and turn it on.
How do you know if a contactor is bad?
These bad AC contactor signs may include:
- Humming. When your AC is on, it may produce a humming sound – but, it won’t power on. …
- Chattering. When the contacts are dirty, or the coil has become weak, you may hear the plunger make a chattering sound. …
Why contactors are used?
Why are Contactors Used? Contactors are used for high power applications. They allow a lower voltage and current to switch a much higher power circuit, so they are generally larger and more heavy-duty than control relays, enabling them to switch higher power loads on and off for many thousands of cycles (Figure 1).
What’s the difference between a relay and a contactor?
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.
What is NO and NC In Contactor?
Relays and contactors have two types of contacts, each suited for different applications: Normally open (NO) contacts allow current when the relay or contactor is energized. … Normally closed (NC) contacts allow current through when the relay or contactor is not energized.
What is contactor and how it works?
A contactor is an electrical device which is used for switching an electrical circuit on or off. … Generally, these electrical devices feature multiple contacts. These contacts are in most cases normally open and provide operating power to the load when the contactor coil is energized.
What is the criteria to select the contactor?
The choice of contactor is dependant upon many parameters i.e. operating voltage, size of contacts, number of operations, ambient temperature, type of load supplied etc. Loads are categorised into various AC ratings, (AC1, AC2, AC3 etc.) and the higher the AC rating the more inductive the load becomes.
Why would a contactor not pull in?
AC contactor not pulling in is not a major issue. … Usually, the contactor malfunctions due to corroded contacts, coil failure, and contactor burnout. 1. Corroded Contacts – The contact points in an AC contactor are susceptible to corrosion because of moisture present in the air.
What causes contactor failure?
Electrical failure – Three different electrical issues can cause contactor failure. The insulation between the coil wires can break down and cause a short. The coil can become grounded through another metal component when the wiring insulation deteriorates. The coil can also become stuck in an open position.
How many ohms should a contactor coil have?
Touch each lead to the coils connectors like reading the voltage, but with the meter in the ohms position. The meter should read from 10 to 100 ohms. If the meter does not, the coil is bad and must be replaced.
Can you bypass a contactor?
A 2-contactor bypass allows a technician to flip the switch, bypass the VFD, and the motor will resume running at 100 percent speed. Eventually, the systems should be shut down in order to safely replace the drive.
When should a contactor be replaced?
Your contactor can fail electrically in one of three ways. The coil can become shorted, grounded, or open. Your technician will use a meter to determine the resistance crossing your contactor. If the readings are outside of a very narrow range; your contactor should be replaced.