Starters are electromechanical devices used to control the starting, stopping, and protection of electric motors. They are commonly employed in industrial, commercial, and residential applications to ensure safe and reliable operation of motor-driven equipment. Starters typically consist of contactors, overload relays, and control circuitry, and they provide various functions such as motor starting, motor stopping, overload protection, and fault detection. Here's an overview of starters and their applications:

1. Components of Starters:

   • Contactor: A contactor is an electromechanical switch that controls the flow of electrical power to the motor. It typically consists of a coil, contacts, and an electromagnetic mechanism that operates based on the principles of electromagnetism.
   • Overload Relay: An overload relay is a protective device that monitors the current drawn by the motor and disconnects the power supply in the event of an overload or excessive current condition. It helps prevent motor damage due to overheating or overloading.
   • Control Circuitry: The control circuitry includes devices such as push buttons, switches, relays, timers, and sensors, which are used to start, stop, and control the operation of the motor.

2. Types of Starters:

   • Direct-On-Line (DOL) Starter: A DOL starter connects the motor directly to the power supply at full voltage during starting. It is suitable for small- to medium-sized motors and applications where the starting current is within acceptable limits.
   • Star-Delta Starter: A star-delta starter initially connects the motor windings in a star configuration to reduce the starting current and torque. After a specified time, the windings are switched to a delta configuration for normal operation. It is used for larger motors and applications where reduced starting current is required.
   • Auto Transformer Starter: An auto transformer starter uses an auto transformer to reduce the voltage applied to the motor during starting, thereby reducing the starting current and torque. It is suitable for medium- to large-sized motors and applications where smooth starting and reduced stress on the electrical supply system are desired.
   • Soft Starter: A soft starter gradually ramps up the voltage applied to the motor during starting, allowing for smooth acceleration and reduced starting current and torque. It is used for applications where precise control of starting characteristics and reduced mechanical stress on the motor and driven equipment are required.
   • Variable Frequency Drive (VFD): A VFD, also known as an adjustable speed drive (ASD) or inverter drive, controls the speed and torque of the motor by varying the frequency and voltage of the electrical supply. It is used for applications where variable speed control, energy savings, and precise control of motor performance are required.

3. Applications of Starters:

   • Starters are used in a wide range of applications where electric motors are employed, including:
     • Industrial machinery and equipment: such as pumps, fans, compressors, conveyors, mixers, and crushers.
     • HVAC (heating, ventilation, and air conditioning) systems: such as air handlers, chillers, cooling towers, and pumps.
     • Water and wastewater treatment facilities: such as pumps, blowers, mixers, and aerators.
     • Manufacturing processes: such as machine tools, presses, extruders, and packaging equipment.
     • Commercial buildings: such as elevators, escalators, lifts, and HVAC systems.
     • Residential appliances: such as refrigerators, washing machines, air conditioners, and garage door openers.

In summary, starters are essential devices used to control the starting, stopping, and protection of electric motors in various industrial, commercial, and residential applications. They provide functions such as motor starting, overload protection, and fault detection, ensuring safe and reliable operation of motor-driven equipment while minimizing energy consumption and mechanical stress on the system.