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DIRECT ON-LINE (DOL) starter: Direct On-Line is the simplest and cheapest method used for starting three-phase motor. Dol is used for up to 5 HP motor. dol starter is more popular due to the low price.  It connects the motor directly to supply without a reduction in supply voltage and apply full line voltage to 3 phase motor.this is the main disadvantage of dol starter.HP motor required special unit called a motor starter.  Three phase induction motors control and power circuit consist MCB or fuse unit which connected in series with the supply. Power contactor, thermal Overload relay for protection and stop and start push button. Working Principle of Direct online starter (DOL Starter ) : 1) To start the motor, start push button is pressed. After that, the main power contactor coil energized due to electromechanical action and this latch contactor pole.it applies full line voltage to the motor terminals. and the motor starts running. The motor will draw a very high inrush curr...

  Star delta starter working principle theory There are many different starting methods are used to start a three-phase induction motor like Star delta starter. One of them, popular and cheapest is a Direct online starter. But its use limited for smaller HP motor, to start higher rating 3 phase motors star-delta starter is used. Star-delta starter is useful where all six terminals of the motor are accessible.  we will discuss star delta starter working principle with help of power and control diagram, Theory, connection wiring diagram, parts like contactor, mcb, fuses, a timer circuit, overload relay. Star-Delta starter is the simplest starting method for reducing the inrush starting current of Induction motor. The starter can be used with all squirrel-cage induction motors that are delta-connected for normal operation.  The reduction of the high motor current causes a reduction of the starting torque of the motor. Star-delta starting is therefore especially suitable for...