A Complete Overview of Direct On Line (DOL) Motor Starters

When choosing a motor starter that is usually used to power industrial and commercial machinery, a lot of consideration is required. There are various types of motor starters, but the most preferred one among engineers and technicians is the Direct On Line (DOL) motor starter. It has been a simple and effective system that was applied many years ago, especially in motor control. In this blog, we will give a brief description of what DOL motor starters are, the types of DOL motor starter, where they are useful, and why they are important. 

What is a DOL Motor Starter?

A direct-on-line (DOL) motor starter is a machine employed to operate and regulate electric motor operations. As the name implies, it links the motor directly to the power supply. This is the reason why it is called direct on line. This method is cheap and efficient; thus, it is used in many applications. 

In the case of a Direct On Line motor starter, when the start button is depressed, the supply voltage is directly applied across the motor, which means that from the instance of starting, the motor is supplied full voltage. Such a starter is commonly used in motors whose starting is not very complicated and hence used mostly in small to medium size motors.  

Types of DOL Starter

DOL motor starters are of many types because they vary depending on the motor's application and power rating. The most common types of DOL starter include:

• Basic DOL Starter: This is the simplest type of DOL motor starter. They include a contactor, an overload, and the start/stop push button. The basic DOL starter is normally recommended in areas where more complex equipment is not required due to cost issues, among other factors.
• Automated DOL Starter: The use of an automated DOL starter comes with the extra benefits of alarms or lights such as timers or sensors. These improvements make it possible to exercise more authority in the control of motor operations, hence optimal results in complex tasks.
• Remote DOL Starter: Remote DOL starters are basically designed for convenience, which permits starting and operating this motor from a distance. This type is particularly beneficial in scenarios where the motor is hard to access or is placed in a risky area. 

3 Phase DOL Motor Starter

The 3-phase DOL motor starter is intended for three-phase motors, which are popular in industrial and commercial applications. A main benefit of a 3-phase DOL motor starter is that it is capable of starting large motors and other complex applications. 

Advantages of 3-Phase DOL Motor Starters:

• High Starting Torque: Three-phase motors are characterised by higher starting torque than single-phase motors and are thus best suited for heavy-duty operations.
• Balanced Load Distribution: The three-phase power supply is able to distribute the load in a balanced manner across the motor and the load, which results in less wear and tear on the motor components.
• Efficient Operation: Three-phase motors are generally more energy-efficient and possess a higher power factor, meaning that they cost less to run than single-phase motors. 

Single Phase DOL Motor Starter 

Single phase DOL motor starter is for single phase motive power, which is frequently encountered in residential and light commercial use motors. These starters are more appropriate for small motors, and the motor control application is more straightforward and compact in design. 

Advantages of a Single Phase DOL Motor Starter

• Cost-Effective: Single-phase DOL starters are mostly cheaper when compared to the three-phase types and can thus be ideal for use in low-power applications.
• Simplicity: In single-phase DOL starters, the designs, though simple, make them rather easy to install and maintain as well.
• Versatility: Single-phase motors are normally found in household appliances and small machines, and therefore, a single phase DOL starter is very useful. 

Applications of DOL Motor Starters

Some common applications of DOL motor starters include:

• Pumps: DOL starters are employed in several applications, such as pump control in water treatment and irrigation, fans, and other applications that require simple and efficient starting circuits. 
• Fans and Blowers: DOL starters are used to operate fans & blower motors for air circulation and heating, ventilating & air conditioning purposes.
• Compressors: DOL motor starters are also used in compressors where a high starting current and absolutely satisfactory operation are advantageous.
• Conveyors: In industrial applications and manufacturing, DOL starters help regulate the movement of the conveyor belt or transport of the products. 

Why DOL Starter Used in Motor?

Below are the reasons why DOL starter is used in motors.

• Simplicity: DOL starters are easy to install and use in an electrical system. They are suitable for most applications, whereby complicated starting procedures are unnecessary.
• Cost-Effectiveness: The low design of DOL starters implies that they are cheaper compared to other motor starters in the market. This cost-effectiveness is especially an added advantage when the cost aspect is an issue.
• Reliability: DOL motor starters are considered to be very reliable and long-lasting in their performance. They are strong and offer reliable and uninterrupted operation to minimise frequent maintenance, thus suitable for several uses.
• Ease of Maintenance: DOL starters are more basic as they include only the essential parts, hence making them easier to maintain and repair than the other motor starters.

Also Read: DOL Starters for Agricultural Motors and Pump Sets

Conclusion

It can be stated that DOL motor starters remain one of the simplest, rather inexpensive, and highly effective ways to manage electric motors. It does not matter if people are dealing with single-phase or three-phase motors; they are all the same when it comes to DOL starters. Its advantages include the simplicity of operation, the comparatively low cost compared to the equipment of other manufacturers, and the reliability of the motors produced. 

Those looking for DOL motor starters or any other electrical products can visit Lauritz Knudsen Electrical and Automation Smartshop, as our online shop is the best for these devices.  We provide a complete line of products that guarantee you to get the most suitable motor starter. Whether you need a basic DOL motor starter or a more professional type, Lauritz Knudsen Electrical and Automation Smartshop offers you all the solutions and services you need to maintain business continuity.