The main heart of dol starter is relay coil. Working principle of dol starter.

Electric Motor Starter Wiring Diagram Harness Down3
Single phase dol starter wiring diagram. Collection of single phase motor starter wiring diagram. Single phase dol starter wiring diagram. Direct on line starter wiring diagram. The dol starter comprises of an mccb or circuit breaker contactor and an overload relay for protection. These two buttons ie. A single phase dol motor starter can be designed using the same components as shown in following diagram.
Normally it gets one phase constant from incoming supply voltage a1when coil gets second phase relay coil energizes and magnet of contactor produce electromagnetic field and due to this plunger of contactor will move and. We have to use all 3 poles of the overload relay otherwise the imbalance due to the current flow in only 2 of them will cause unnecessary tripping. A direct online starter consits of two buttons a green button for starting and a red for stopping purpose of the motor. Please see the attached diagram for guidance. It reveals the parts of the circuit as simplified shapes and the power and signal links between the gadgets. This diagram illustrates possible wiring using a tesys d lc1d contactor and tesys lrd overload lrd and stop control is assumed to be by operation of the stop button on the overload.
The diagram below shows the wiring for a single phase motor and the path through the contactor and overload. Green and red or start and stop buttons control the contacts. The wiring diagram for a dol stater is shown below. A wiring diagram is a simplified traditional photographic representation of an electric circuit.