The Basic Construction and Sizing of a Contactor

by Tyron

So, you are determined to acquire or buy a contactor switch, impressive move! There are basic criteria used to find a top-notch switch for different applications. It is the objective of experienced professionals to ensure that the process is pretty simple. Looking into the history of contactor switches, it might be of some help to garner general comprehension of what their function is in different industrial applications.

As you have garnered from different blog posts in this series, a DC contactor is controlled by a switch. This device comes in various capacities. It also has different features.

And unlike in a circuit breaker, the device is not intended to interfere with the short circuit current. Contactors come in several amperes to several kilovolts.

Therefore, the size of a contactor actually ranges from a small device to a large one depending on its actual applications.

Contactors are generally used in controlling electric motors, thermal evaporators, as well as other additional electrical loads.

Understanding Basic Construction and Size

Before you delve into the process of selecting the contactor for your project, you should comprehend its basic anatomy. Here are the fundamentals of the device.

A contactor comes in three main components:

The contact is responsible for carrying the fundamental part of the entire contactor. This covers power contacts, contact springs, in addition to the auxiliary contacts.

Then, there is the electromagnet, which offers a major driving force to the contacts.

And finally, the contactor has a frame that houses it. It is known as an enclosure and is made of various insulating materials such as a thermoplastic.  

The enclosure is also known for its properties of insulating the contacts while protecting the user from touching the contacts.

A basic DC or AC contactor comes with a coil input. The coil can easily be energized with a voltage.

Choosing the Right Contactor Size

Check the coil ratings

· The coil ratings of a contactor will determine its size in many ways. So you need to take a look at the following elements when making your selection:

· The pick-up voltage which refers to the switch that should be in the operating position

· The motor’s pick-up voltage is highly considered in the selection process

· The rated coil voltage-  must be equal to the volt of the circuit that powers the coils when selecting a contractor

· Consider the operating current of the contactor since it is rated in volts and should determine the size of contactor you are investing in a contactor

Check the electrical properties of the device

The impressive electrical characteristics of a motor need to be analyzed and studied in detail for you to be able to select the right contactor for a motor.

Some of the common properties are also highly regarded and mentioned when it comes to choosing the right motor.

Attention is given to the parameters of power within the motor, which can be the hose power and motor voltage.

To be precise and accurate in selecting the right contactor size, you should have a data sheet. This should help you to determine the properties of the motor.

Final Thoughts

Deciding the power supply for your contactor is an excellent determinant in choosing the right size. This is also a great move towards selecting the right device for your electrical projects.  If you would rather have the control unit using the PLC, you can use the 24 VDC.

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