DESIGN AND CONSTRUCTION OF A DIRECT ON-LINE MOTOR STARTER
Abstract
This project presents the design and construction of a Direct On-Line (DOL) motor starter, intended for the protection and control of three-phase squirrel cage induction motors during startup. The DOL starter delivers full line voltage directly to the motor terminals, ensuring rapid acceleration to full speed. The design incorporates essential components including a three-pole electromagnetic contactor for switching, thermal overload relays for motor protection against excessive current, and a control circuit comprising start and stop push buttons with auxiliary contacts for interlocking and safety. Detailed calculations for the selection of contactor ratings and overload relay settings performed based on the motor’s rated current and service conditions. The construction involves assembling the control panel with appropriate wiring according to industrial standards and testing under simulated load conditions to verify the functionality and reliability of the starter. This project demonstrates a cost-effective and robust solution for motor starting applications, providing fundamental insights into motor control circuitry and protection techniques.
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