What Is Direct-On-Line Starter (D.O.L.)

DIRECT-ON-LINE STARTER (D.O.L.)

✴️ DOL starter full form is Direct-on-line. When the green button (start in Fig.) is pressed, it causes the contacts to make contact and then electro-magnet becomes magnetized and attracts metallic strips to short respectively L1, L2 and L3 to M1, M2 and M3 through overload release heating elements. If due to any reason (overload or fault, or single phasing), the load current is increased, the overload strips bend and disconnect the electric circuit of no-volt coil through a switch. The no-volt coil becomes demagnetized and all the strips will come to their original positions and motor will stop.

No-volt coil circuit is shown separately. 

DIRECT-ON-LINE STARTER (D.O.L.)

Note that  - 

1. No-volt coil IS connected with two phases.

2. Start push, overload relay, stop push and coil is connected in series with each other, and then connected to two phases.

3.Interlock switch is connected in parallel with start push.

4. When the start push button is pushed circuit is L3-NVC stop, OLR, AB, ON to L1.In this way, the plunger is pushed downward and the interlock switch is also pushed downward. Now when the start push is released, the circuit becomes L3 -N.V.C. stop,. OLR, to interlock to L1.

5. Remote control : With the help of this control the motor can be started or stopped from anywhere even if the starter and motor is placed at other place. The separate switch unit is available for remote control, the circuit diagram is shown in Fig.

(a) 3 points (terminals) have been taken from the starter circuit on L and two others by disconnecting at A and B.

(b) ’On push’ of remote control is connected in series with stop switch of starter.
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