Product: Direct On Line (DOL) Starter

Model: NQ3-11P

Brand: Chint

Coil voltage: optional (220v/440v)

Power: 17~25 Amp = 15 HP/11 KW

Rated frequency: 50 Hz

Protection rating:IP55

Standard: IEC/EN60947-1

Specification

• DOL starter (or Direct On Line starter or across the line starter) is a method of starting of an induction motor.
• In DOL Starter an induction motor is connected directly across its supply, and the DOL starter applies the full line voltage to the motor terminals.
• Despite this direct connection, no harm is done to the motor.
• A DOL motor starter contains protection devices, and in some cases, condition monitoring.
• A direct on line starter can only be used if the high inrush current of the motor does not cause an excessive voltage drop in the supply circuit.
• If a high voltage drop needs to be avoided, a star delta starter should be used instead.
• Direct on line starters are commonly used to start small motors, especially 3 phase squirrel cage induction motors.

Working

• A direct online starter consits of two buttons, a GREEN button for starting and a RED for stopping purpose of the motor.
• The DOL starter comprises of a contactor and an overload relay for protection.
• These two buttons, i.e. Green and Red or start and stop buttons control the contacts.
• To start the motor, we close the contact by pushing Green Button, and the full line voltage appears to the motor.
• A contactor can be of 3 poles or 4-poles, It contains three NO (normally open) contacts that connect the motor to supply lines, and the fourth contact is hold on contact (auxiliary contact) which energizes the contactor coil after the start button is released.
• If any fault occurs, the auxiliary coil gets de-energized, and hence the starter disconnects the motor from supply mains.
• If we press the stop button, the current through the contact becomes discontinued, hence supply to the motor will not be available, and the similar thing will happen when the overload relay operates.
• Since the supply of motor breaks, the machine will come to rest.
• The contactor coil (Magnetizing Coil) gets supply even though we release start button because when we release start button, it will get supply from the primary contacts.