Motor Starter Contactor

July 28, 2023 Post a Comment

Motor starter contactor

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.

Why contactor is used in starter?

Protection of the internal thyristors: the line contactor isolates the soft starter and protects the internal thyristors from any problems present on the network, like severe voltage spikes on the incoming line, such as lightning strikes or downed power line, etc…

Why contactor is used in motor?

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).

How do you test a starter motor contactor?

It is best to check this on the cable going into the contactor at terminals L1, L2, and L3, or if there is a disconnect switch, check the incoming wires to the disconnect. Measure between the legs L1, L2, and L3 to verify you have full voltage according to your input line power to the motor.

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

A Motor Starter is a basically a contactor with the addition of an overload relay which will drop out the coil voltage in case of motor overload condition. A Contactor is an electrically control switch same as a relay. It is used for switching the current to ON and OFF a circuit.

Does a motor need a contactor?

Summary. – We use a contactor to turn on and off heavy and high voltage electrical devices such as motors, fans, pumps, etc. – The reason that we use a contactor is to control these heavy high voltage electrical devices indirectly and safely via a PLC and not to connect the PLC directly to these output devices.

What is a 3 phase motor contactor?

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.

What is the difference between relay and contactor?

Relays are used to control contacts of an electrical circuit due to a change of parameters or conditions in the same circuit or any other associated circuit. Contactors, on the other hand, are used to interrupt or establish connections in an electrical circuit repeatedly under different conditions.

What are motor starter contacts made of?

The material of choice, however, is most often silver-cadmium oxide. The mix is usually 85/15 or 90/10. These contacts are found in most AC contactors for NEMA size 00-6. A 50/50 silver tungsten mix is used for high-amp applications.

What is 13 and 14 on a contactor?

Many contactor manufacturers use the designations A1 and A2 for the terminals that connect power to the magnetic coil. Likewise, many manufacturers use the designations 13 and 14 for the terminals of normally open auxiliary contacts. Auxiliary contacts are operated by the magnetic coil just like the main contacts.

What is contactor and its function?

A contactor is an electromagnetic device that is used for switching an electrical power circuit on or off. It is a multi-pole switch i.e. multiple power circuits can be controlled by a single contactor. As it is controlled by electromagnetism, we don't have to switch on or switch off it manually.

How do you select a contactor for a motor?

There are 5 primary things to consider when determining how to size a contactor for your application:

Full Load Amperage at Line Voltage. The first item to consider is the load, which is measured in amperes.
Contactor Coil Voltage. ...
IEC Utilization Categories. ...
Reversing vs Non-Reversing Contactors. ...
Auxiliary Contacts.

How do you know if your contactor is bad?

To test the contactor, you'll need a multimeter (available at any hardware or big box store). Set it to the “OL” setting. Connect the multimeter to the low volt terminals on both sides of the contactor. If the contactor is working properly, the multimeter will show a reading between 5 and 20.

What causes a contactor to fail?

By far the most common cause of contactor coil failure is, surprisingly to many, undervoltage. There may be sufficient voltage to pull the contactor in, but not enough to keep the coil armature formers firmly "sealed".

How do you diagnose a bad contactor?

A bad AC contactor can be identified by physical signs of deterioration, also known as pitting. Pitting occurs when the contactor has encountered extreme voltage and heat. A pitted contactor tends to stick, causing a continuous flow of electricity to the unit.

Can I use a 3 phase contactor for a single phase motor?

Single phase motor starters are not commonly available since this is a rare case, and with a little bit of know-how, a 3-phase motor starter can easily be wired for single phase power.

What is the most common cause of motor failure?

Winding insulation breakdown and bearing wear are the two most common causes of motor failure, but those conditions arise for many different reasons.

What are the 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.

What is A1 and A2 in contactor?

A1 and A2 on a contactor typically refer to either end of the electromagnetic coil assembly. Most contactor manufacturers use A1 and A2 to designate the two terminals connecting electrical power to the contactor's magnetic coil.

What is the difference between a contactor and a switch?

Relays are switching devices used in any control circuit for checking a condition or multiplying the number of contacts available. Contactors are switching devices used to control power flow to any load. Mainly used in control and automation circuits, protection circuits, and for switching small electronic circuits.