Why are mechanical motor starters still used?

The simple answer is they work well. And in some scenarios mechanical starters offer better performance or are the better option. In high voltage operations they offer superior performance and reliability. Additionally, they offer the ability to interrupt the flow of current almost instantly (even tolerating high voltage arcing). This makes mechanical starters the preferred solution in production lines (e.g., conveyor systems) and in situations when starting and stopping is repeated (e.g., cranes, elevators, etc.).

What is a mechanical starter?

A mechanical starter is a simple device that opens or closes a circuit mechanically. It generally consists of the contactor which contains a control coil and shunts. The shunts convey current to the control coil energizing it, the coil then creates a magnetic field that opens or closes the contactor. The electrical contactor also has stationary and movable contacts. When the coil is energized the magnetic field "mechanically moves" the contactor to close or open the contacts.

The uncomplicated and dependable operation of a mechanical starter often makes it the best choice. For instance, when devices are handling over 15 amperes or more than a few kilowatts, contactors are superior to relays or electrical starter solutions. Electrical contacts can also handle higher voltages and operate well using either AC or DC current. Contactors also tolerate "dirtier" conditions better than electronic control solutions. That’s why you’ll find electromagnetic motor starters in process plants, heavy lift cranes, gantry cranes, mining operations, and anywhere conditions can be "messy".

Electromagnetic-mechanical starters come in all forms

Just like motors, electrical contactors and coils in mechanical starters come in all shapes and sizes. Performance requirements and function determine their shape and type - but the basic operation of contactors and the mechanical starter remains the same. The coil is energized, the movable contacts open or close and the flow of current to the motor is regulated.

It’s the simplicity and reliability of a mechanical motor starter that continues to make it a preferred standard - even in today’s digital world.