What is DOL starter

 A DOL starter, also known as a Direct-On-Line starter, is a type of motor starter used to start and control the operation of electric motors. It is one of the simplest and most common methods of starting motors in industrial and commercial applications.

The DOL starter consists of a contactor, an overload relay, and a start and stop push button. The contactor is an electrical switch that controls the flow of electricity to the motor. The overload relay is a protective device that monitors the motor's current and protects it from damage in case of overloading or excessive current.

When the start button is pressed, the contactor closes, allowing electricity to flow directly to the motor. This results in an immediate full-voltage connection to the motor windings, causing the motor to start running at its rated speed. The overload relay protects the motor by sensing the current passing through the motor and disconnecting the power supply if it exceeds the predetermined threshold.

DOL starters are commonly used for smaller motors, typically up to a few kilowatts. They are suitable for applications where the starting current surge is not a concern and where the mechanical load on the motor is light at startup. However, for larger motors or applications with heavy starting loads, alternative starting methods like star-delta starters or soft starters may be used to reduce the inrush current and minimize mechanical stress on the motor.

It's important to note that while DOL starters provide a simple and cost-effective starting method, they can cause a significant voltage dip in the power supply when the motor starts. This voltage dip may affect other equipment connected to the same power supply.