A Guide to the Four Basic Functions of a Motor Starter

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  • Author Shamrock Controls
  • Published November 27, 2019
  • Word count 523

What is a motor starter?

A motor starter is an electrical device that controls the electrical power for starting a motor. It can also stop, reverse, and protect the motor. The two major components of a start include a contractor and an overload relay.

What is a contractor?

The contractor controls the electric current to the motor. It can also make or break the power that goes through the circuit.

What is an overload relay?

The overload relay prevents the motor from burning out when it overheats. That’s how it protects the motor from potential damage.

What are the types of starters?

The two most basic types of starters include manual starters and magnetic motor starters. The first one only requires manual operation to work, which makes for a unit that is easy to use. Operators are not required to get expert intervention. The second option, though, works electromagnetically.

What are the functions of a motor starter?

A motor starter has four basic functions. These include:

• Control

• Protection from a short-circuit

• Protection from overload

• Disconnect and Break current

What are the control functions?

The control function refers to the role of the starter in closing and opening an electrical power unit. The main contacts or poles of the contractor is where the switching occurs. When an electromagnetic coil is energized, this opens or closes the contacts.

How does it protect against a Short Circuit?

When normal load currents jump, the short circuit steps in. The short-circuit disconnects the supply. That prevents severe damage to the system. Fuses are used to break or connect currents, along with circuit breakers.

What is overload protection?

A motor may sometimes draw more current that it is capable of handling. That’s when an overload happens. The overload relay works to identify the excess currents, which alerts the auxiliary contact of the relay. It opens the circuit to keep the motor from burning out. It also prevents overheating of the motor. The overload relay, along with the contractor, provides the motor with ample overload protection.

How does it disconnect and break the current?

The motor must be disconnected from the main power circuit before it restarts. To isolate it from power and switch it off, the disconnect switch or circuit breaker makes this happen. Operators use this to perform maintenance on a motor or starter. They isolate the unit from the main power line before they carry out repairs and system checks.

Where do you buy a motor starter?

Shopping online is easy. You get plenty of options. But be careful to ensure that you buy from reputable sources. Don’t take the risk of ordering from a dicey site. Check the information about the site, its products, and the people behind it. Consider its qualifications and credentials. Is it trustworthy? Once you tick off that box, cover the basics: look for discount promos and free shipping offers. Check reviews about the site and its products. Consider its customer service levels and go over its return policy. By the time you take all these steps, you’ll have a better idea of which site hits the mark.

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