ELECTRICAL INSTALLATION SYSTEMS

Applications of direct online Starter ✅DOL starters are used to start small-rating motors like water pumps, compressors, conveyors, etc. The compressor motor starts at no load; therefore, this starter is suitable for compressor motors.

Disadvantages of DOL Starter ✅The starting current is high (5-8 times the full load current), so a higher rating of switch gears is required to be installed. ✅Direct online Starter causes a significant dip in voltage, hence suitable only for small motors. However, it can be used to start a large-rated motor up to 90 KW if the power transformer capacity permits. ✅DOL Starter reduces the lifespan of the machine because of higher thermal and mechanical stresses on the system.

ADVANTAGES ✅Simple and most economical starter. ✅More comfortable to design, operate and control ✅It provides nearly full starting torque at starting ✅Easy to understand and trouble shoot ✅DOL starter connects the supply to the delta winding of the motor.

Working Stages of DOL Starter ✅When the start push button S2 is pressed the contactor KM1 is energized and the Motor is connected directly on line/supply. ✅The contact KM1 (13-14 auxiliary contact) get closed and keeps the contactor ON when the push button is released(Holding contacts) ✅When the stop push button is pressed, it Stops the operation of the circuit.

Control circuit

The main components of Power circuit are; ✅Fused isolator/Circuit breaker(Short circuit protection) ✅Contactor (Switching) ✅Overload relay (Running overcurrent) protection

DIRECT ONLINE STARTING METHOD ✅It directly connects the contacts of the motor to the full supply voltage. ✅The starting current is very large, normally 6 to 8 times the rated current. ✅In order to avoid excessive voltage drops in the supply line due to high starting currents, ✅The DOL starter is used only for motors with a rating of less than 10 H.P ✅POWER CIRCUIT- is a circuit used to supply electric energy to the motor. ✅CONTROL CIRCUIT- is a circuit used to supply control components in the motor control circuit. . ✅POWER CIRCUIT + CONTROL CIRCUIT= COMPLETE MOTOR CONTROL CIRCUIT ✅The Direct-on-Line Starter usually mainly consists of two parts: ✅Control Part – Contactors and Push Buttons ✅Protection Part – Overload Relay

THE COMMON METHODS OF STARTING 3-PHASE INDUCTION MOTOR . Three types of starters are mainly used for starting a squirrel cage induction motor. ✅DOL( Direct Online Starter) ✅Star Delta Starter ✅Resistance starter ✅Auto transformer starter ✅Soft Starter ✅Variable frequency Drive ( Used for soft starting and speed control)

A motor starter is made of two main components that work together to control and protect the motor; ✔️Electrical Contactor: The purpose of the contactor is to switch ON/OFF the power supply to the motor by making or breaking the contact terminals. ✔️Overload protection circuit: The purpose of this circuit is to protect the motor from potential harm due to the overload condition. Huge current through the rotor may damage the winding as well as other appliances connected to the supply. It senses the current & breaks the power supply.

✅A motor starter is an electrical device that is used to start & stop a motor safely. The motor starter switches the power ON/OFF. . ✔️The main function of a motor starter is; ✅To safely start a motor ✅To safely stop a motor ✅To reverse the direction of a motor ✅To protect the motor from low voltage & overcurrent.

✅INDUCTION MOTOR STARTING METHODS

Motor terminal block connected in DELTA

Motor terminal block connected in Star

DELTA CONNECTION A connection where three dissimilar ends (Start and finish) of three phase windings are joined together.