I work with many electrical motors. The most common starting method I have ever seen is DOL, direct online.
However, Star Delta and VSD starters, are also used for larger motors. In this article let’s discuss DOL starter vs Star Delta starter.
Table of Contents
What is a DOL starter?
What is Star-Delta Starter?
Star Delta vs DOL table
|DOL Starter||Star Delta Starter|
|The motor starts on its full starting torque||Starts motor on third of its starting torque|
|Motor starts at full starting current||Reduces starting current|
|Very simple and needs just one contactor||More complicated in design and needs 3 contactors|
|Suitable for high starting torque applications||Not good for applications with high starting torque|
|Lower cost, and requires less maintenance||Costs more, and requires more maintenance|
|Works for motors with Delta or Star connection||The motor must be designed to work on the Delta connection|
|Full voltage is applied to the motor at the starting||The voltage is reduced to a lower value|
Now let’s dive into some details of DOL starter vs Star Delta starter
dol starter circuit diagram
DOL starter circuit consists of, a contactor, overload relay, start button, and stop button.
These components are used for control and protection purposes.
In case of a fault condition, the contactor opens with the help of a thermal overloaded relay.
The contactor is also controlled by the start and stop buttons.
When the motor is working the contactors are electrically closed. To stop the motor, just press the stop button to de-energize the contactor.
Star Delta starter circuit diagram
In the case of a star delta starter, the power supply source to the motor is connected to the delta connection from a star with the help of wiring.
In this process, full voltage is applied to the motor when it is running and in this way, full torque is obtained as an output.
The star delta starter is used to start the motor and when it gets the speed after starting it is converted to the delta.
Star connection starts the motor with less voltage and the motor takes time to get the speed in this mode.
As we know the torque is proportional to the square of voltage that’s why the starting torque also reduces in the star mod.
when to use DOL and Star Delta starter
Star and Delta Motor Terminals
In the case of a star delta starter, the motor is connected in such a way that it can be switched over from star to delta.
To complete this task the six ends of the winding of the motor are connected to the terminals. Then the starter switch of star delta starter performs its action of switching over the motor accordingly.
The working system of the DOL starters is different. It requires only one set of cables from the starter to the motor.
That wire and the single switch perform all the tasks. That is the reason the DOL starter is easier to troubleshoot and understand.