Different Kinds of Contactors You May Need to Know

by Robert P.

An automotive contactor is a large relay that is electrically controlled. It is used for switching an electrical circuit on and off, hence protecting the motor from external power damage. It acts as a passage through which electric current flows. It is used in 3 phase applications such as electric motors and lighting applications with higher current carrying capacity. They come in different sizes, i.e., can be handheld or a large one measuring up to a meter. We look at the various types of contactors down below.

Types of Contactors

· Magnetic Contactors

These are the most common type in industrial applications. They are a form of electrical relay found in motors that are powered by electricity. They balance out changes in electrical frequency between the primary power sources and engines with high voltage capacity. You should note that they are not circuit breakers and can be separated from the motor when the current is off to allow for maintenance. Secondly, they are made of heat resistant and non-conductive material and have two contacts, one with a magnetic coil and the other with an iron core. When electricity flows through, a magnetic field is created, and the iron core is pulled towards the magnetic coil creating an electric arc.   

A magnetic contactor is automatic; thus, it does not require any manual operation. This helps to eliminate human-related risks and prevents any operator from potential danger that may arise, making it safe and efficient. It saves on energy as only a small amount is needed to open and close the circuit.

· Knife Blade Switch

It is a type of switch that regulates the flow of electricity in a circuit. There is a metal strip that acts as the switch. The strip drops on contact, and a lever pulls the switch up or pushes it down. The knife blade switch contactor is rare nowadays as the switching process was too fast and could not be controlled manually. It underwent corrosion and became less efficient. Over the years, the motors’ size increased, leading to increased demand in current volumes that were required to operate it. The high levels of current were a serious safety problem, making it difficult to manage. Its exposed metal parts also posed a high risk of electric shock and could cause fire or explosions in certain conditions.

· Manual Controller

It was developed after the knife blade contactor. It offered better safety and extra features that were not available in the previous design. Its new features include; reduced motor size making it easy and safe to operate, double break contacts which open the circuit simultaneously in two places and a case for the unit. The contactor is 100% manual as the switch is physically attached to the controller. Once a personnel activates the controller, the power circuit becomes engaged, and the current is carried to the load.

Bottom Line

Contractors are essential as they protect large electric motors from any damage caused by an overcurrent. There are various types, and each has its applications and capabilities, so choose one that fits your specific needs.

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