DOL Starter (Direct Online Starter) is also known as “across the line starter”. DOL starter is a device consist of the main contactor, protective devices, and overload relay which is used for motor starting operations. It is used for low ratings usually below 5HP motors.
In the direct online starter method of motor starting, the motor stator windings are directly connected to the main supply where the DOL protects the motor circuit from high inrush current which may damage the overall circuit as the initial current is much higher than the full rated current.
- It is very simple to design, operate and maintain.
- It is the most cheapest and economical starter.
- It has a compact design and occupies less space.
- It provides 100% of the starting torque.
- The control circuit (green and red button) is simple and a layperson can operate it.
- Understanding and troubleshooting the system is easier.
- It connects the delta winding of the motor.
- As it utilizes the full voltage starting technique, the starting current is very high.
- The starting high current may damage the motor thus only low rating motors should be used.
- The high inrush current causes a voltage dip in the power lines that can be dangerous for other appliances connected in parallel.
- The high starting torque can be unnecessary in some cases.
- High starting torque causes mechanical stress reducing the life span of the motor itself.
- There is no control over the starting current and torque.
Some of the features of DOL starters are following;
- It provides a high starting current.
- It provides high starting torque.
- It causes a voltage dip in the power mains.
- It has the simplest controlling mechanism.
- It is suitable for low power rated motor.
- The DOL starters are used for motors having low power ratings.
- Where the starting current does not damage the windings of the motor.
- For applications where the starting current does not cause huge dips in the line voltage.
- Direct online starters are used for small water pumps, conveyor belts, fans, and compressors.
THE INFINITY CORPORATION is one of the leading suppliers of motor starter products all over India.