• The main supply is connected to the contactor, which, when energized, connects the A.C motor to the supply.
• The START push button activates the contactor, allowing the motor to start running.
• Overload protection (O/L Relay) and Single Phase Protection Relay are connected in series with the contactor in the control circuit.
• If any protection device detects a fault (e.g., overload or single phasing), the contactor drops, opening the normally closed (NC) contacts and stopping the motor.
• The STOP push button also causes the contactor to drop, stopping the motor.
• The START and STOP push buttons can be located remotely for remote operation of the motor.
• The contactor has a solenoid with normally open (NO) and normally closed (NC) contacts, facilitating the control system's requirements.
• The main electrical equipment is connected to the supply through the contacts of the contactor, ensuring controlled motor operation and protection against faults.

Disadvantages of DOL starter:

• Direct-on-line starting of a squirrel cage induction motor results in a high inrush current, typically 6 to 8 times the rated full-load current. This high current can cause voltage dips and disturbances in the electrical system, especially when starting large motors. It can also lead to excessive heating of the motor windings and reduced motor life.

• The direct-on-line starting method produces high starting torque, which can be excessive for some applications. This high torque can cause mechanical stress on the motor

• The high starting current of a direct-on-line start motor can cause voltage fluctuations in the electrical system. These voltage fluctuations can affect other sensitive equipment connected to the same electrical network, potentially causing malfunctions or disruptions.

• Direct-on-line starting is not suitable for applications where a soft start or controlled acceleration is required. It is also not recommended for motors that are frequently started and stopped, as the high starting current and torque can cause premature motor failure.