How to Connect a Direct online Starter (DOL Starter)

Summary

In this instructional video, the presenter demonstrates how to connect a direct online starter, used for small motors or pumps, to a three-phase power supply. The process involves connecting the supply lines to the contactor's L1, L2, and L3 terminals and ensuring the contactor's voltage matches the supply. The overload is connected in line with the supply, and the contactor's coil is wired through a start-stop switch. The video also explains the importance of the normally open and normally closed contacts for the overload and contactor, and the role of the holding contact in maintaining the contactor's engagement. The presenter concludes with a test of the starter and a tip on how to identify and fix common issues with the starter's lid.

Takeaways

• 🔌 The direct online starter is used for starting small motors or pumps and includes a contact and overload for safety.
• ⚡ It is designed for three-phase supply, with connections to L1, L2, and L3, ensuring the contactor's voltage matches the supply.
• 🔗 The overload is connected in line with the supply wires to protect the motor from excessive current.
• 🔁 The contactor's coil has two power points, A1 and A2, which can be connected to the supply for operation.
• 🔄 A bridge is created between L1 and A1, and wires are run from L3 to the normally open contact on the contactor.
• 🔲 The start button is wired to the normally open contact of the contactor and to the normally closed contact of the overload.
• 🔕 The normally closed contact of the overload is crucial for stopping the contactor in case of a motor problem.
• 🛠️ If the starter doesn't operate correctly after the lid is put on, check for issues with the internal pins that connect to the buttons.
• 🔓 The normally open contact on the contactor acts as a holding contact, ensuring the contactor stays engaged when the start button is pressed.
• 🎯 Some contactors have a feature where the normally open contact slides onto the contactor, eliminating the need for a separate holding contact.

Q & A

What is the purpose of a direct online starter?

A direct online starter is used for starting small motors or pumps. It has a contact inside and an overload, unlike a manual motor starter which only starts and stops.

What type of supply is typically connected to a direct online starter?

A direct online starter is usually connected to a three-phase supply, as indicated by the use of red, yellow, and blue wires for L1, L2, and L3 respectively.

Why is it important to match the contactor voltage with the supply voltage?

It is crucial to ensure the contactor's voltage matches the supply voltage to prevent damage to the equipment. In the script, a 400-volt contactor is used for a 400-volt 3-phase supply.

How are the overloads connected in relation to the supply lines?

The overloads are connected in line with the supply lines L1, L2, and L3 to protect the motor from excessive current that could cause damage.

What is the function of the normally open and normally closed contacts on the overload?

The normally closed contacts on the overload are used to stop the contactor from switching on if there's a problem with the motor, while the normally open contacts are part of the holding mechanism that keeps the contactor engaged when the start button is pressed.

Why is it necessary to connect wires from the start button to both the normally open of the contactor and the normally closed of the overload?

Connecting wires from the start button to the normally open of the contactor and the normally closed of the overload ensures that the motor starts when the start button is pressed and stops when the stop button is pressed, providing control and safety.

What happens if the normally open contact of the contactor is disconnected?

If the normally open contact of the contactor is disconnected, the contactor will not stay engaged when the start button is pressed, which means the motor will not run continuously as intended.

What is the role of the holding contact in a direct online starter?

The holding contact, or normally open contact on the contactor, holds the contactor in the engaged position once the start button is pressed, ensuring continuous power supply to the motor.

Why might the starter not work properly when the lid is put on after testing without it?

If the starter doesn't work properly after the lid is put on, it could be due to the internal pins not making proper contact with the start and stop buttons, possibly due to paint or incorrect alignment.

What is the significance of the green button mentioned in the script?

The green button is a feature that, when pressed, stays in place and holds the contactor engaged without the need for the normally open contact, providing a convenient way to maintain power to the motor.