Charlotte Miller

What Is DOL Starter?

Are you curious to know what is DOL starter? You have come to the right place as I am going to tell you everything about DOL starter in a very simple explanation. Without further discussion let’s begin to know what is DOL starter?

In the domain of electrical engineering, the DOL (Direct-On-Line) starter stands as a fundamental component that kickstarts the operation of induction motors, facilitating their efficient and reliable performance. Let’s explore the essence of the DOL starter, its functionality, and its pivotal role in empowering the journey of induction motors in various industrial and commercial applications.

What Is DOL Starter?

The Direct-On-Line (DOL) starter is a straightforward yet indispensable device used to initiate and control the operation of induction motors, particularly in scenarios where high starting torque is required. It serves as a simple and cost-effective method for starting and stopping motors by directly connecting them to the power supply.

Functionality And Operation

  • Starting Procedure: Upon activation, the DOL starter directly connects the motor to the power supply, providing full line voltage to the motor windings. This results in the motor starting at its maximum speed and torque.
  • Starting Current: As the motor starts at full voltage, it draws a high starting current, causing a sudden rush of electricity that can impact the system and cause voltage drops.
  • Switching to Running Mode: Once the motor reaches its rated speed, the DOL starter maintains the connection to the power supply, enabling the motor to continue running at its designated speed.

Significance And Applications

  • Simplicity and Reliability: DOL starters are prized for their simplicity, reliability, and ease of implementation, making them suitable for various industrial applications requiring high starting torque.
  • Induction Motor Compatibility: They are commonly employed with squirrel-cage induction motors, particularly in scenarios where a high starting torque is essential, such as in conveyor belts, pumps, compressors, and certain types of machinery.
  • Cost-Effectiveness: As compared to more complex motor starting methods like soft starters or variable frequency drives (VFDs), DOL starters are more cost-effective and simpler in design.

Safety Considerations

While DOL starters offer simplicity and reliability, the high inrush current during the starting phase can impact the power supply and cause voltage dips. This factor should be considered when designing electrical systems to ensure stability and prevent potential disruptions.


The DOL starter serves as a cornerstone in the realm of motor control, providing a straightforward yet effective method to initiate the operation of induction motors across various industrial and commercial applications. Its simplicity, reliability, and capability to deliver high starting torque make it a vital component in powering a multitude of machinery, enabling the smooth and efficient functioning of essential systems in the modern world.


What Is The Purpose Of DOL Starter?

DOL starters are used for motors with low power ratings where the starting current does not damage the motor windings. Direct online starters are used for small water pumps, conveyor belts, fans, and compressors when the starting current does not produce significant fluctuations in the line voltage.

What Is DOL Starter And Star Delta?

DOL starter is the suitable and cheapest method to start up a motor only for more normal sizes motors, larger motors must use the star-delta starter.

What Is A DOL Contactor?

The main objective of the contactor is to control the machinery that uses electric motors. It consists of a coil that is connected to the voltage sounds and quite often for the single-phase motors, 230 V coils are used and for three-phase, 415V coils.

Is DOL Starter Used For Hp?

Direct-on-line starting (DOL): As the name suggests, direct-on-line starting means that the motor is started by connecting it directly to the supply at the rated voltage. Direct-on-line starting, (DOL), is suitable for stable supplies and small induction motors up to 5HP.

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