Construction and Working
Here, will have Construction, Working and Connection of DOL Starter given below :
Construction
The three-phase power supply lines (L1, L2, L3) to the DOL starter are connected in which L1 and L2 are connected to the main contacts of the contactor, while L3 is connected to the common point of the contactor coil as seen the diagram of construction of DOL starter. The three-phase leads from the motor to the other side of the contactor’s main contacts which connect the overload relay in series with one of the motor phases. Therefore, the start button in parallel with the contactor coil is connected and the stop button in parallel with the start button is connected for the working of the starter.
It consists of a coil-operated contractor C controlled by start and stop push buttons which may be installed at convenient places remote from the starter. On pressing the START push button S1 (which is normally held open by a spring) the contactor coil is energized from two line conductors L1 and L2. The three main contacts M and the auxiliary contact A close and terminals A and B are short-circuited.
The motor is thus connected to the supply. When the pressure on S1 is released, it moves back under spring action. Even the coil C remains energized through AB. Thus, the main contacts M remain closed and the motor continues to get supply. For this reason, contact A is called hold-on-contact.
Construction of DOL Starter
Working of DOL Starter
On pressing the START push button S1 (which is normally held open by a spring) the contactor coil is energized from two line conductors L1 and L2. The three main contacts M and the auxiliary contact A close and terminals A and B are short-circuited as seen in the above image. The motor is thus connected to the supply. When the pressure on S1 is released, it moves back under spring action.
Even the coil C remains energized through AB. Thus, the main contacts M remain closed and the motor continues to get supply. For this reason, contact A is called hold-on-contact.
When the STOP push button S2 (normally held closed by a spring) is pressed, the supply through the contactor coil C is disconnected. Since coil C is de-energized, the main contacts M and the auxiliary contact are opened. The supply to the motor is disconnected from the supply.
DOL Starter
For cases to avoid damage to the motor, various techniques are used to reduce the starting current with the use of a motor starter, these techniques vary on different factors and also protect the motor from overcurrent and overloading. DOL starter is one of the techniques used and in this article, we are going to discuss DOL starters and the starting of induction motors. We will cover what is starting induction motors and their functions, what are DOL starters, their application, terminologies, theory, construction, working, and the difference between DOL and star-delta starters.
Table of Content
- DOL Starter
- Important Terminologies
- Construction and Working
- 3 Phase Motor Starter with Overload Protection
- DOL Starter Wiring Diagram
- Advantages , Disadvantages and Applications