Simulation 2D - How to wire direct online starter ? Wiring tutorial D.O.L
A *Direct Online (DOL) Starter* is the simplest way to start a 3-phase induction motor by connecting it directly to the power supply.
To wire a DOL starter properly, you need to divide the task into two parts: the *Power Circuit* and the **Control Circuit**.
1. Components Required
*Main Circuit Breaker (MCB/MCCB):* For short-circuit protection.
*Magnetic Contactor:* To switch the power on/off.
*Thermal Overload Relay (OLR):* To protect the motor from overheating/overcurrent.
*Start Push Button (NO - Green):* To initiate the circuit.
*Stop Push Button (NC - Red):* To break the circuit.
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2. Power Circuit Wiring
This circuit carries the high voltage to the motor.
1. *Supply to Breaker:* Connect the 3-phase incoming supply () to the input terminals of the Circuit Breaker.
2. *Breaker to Contactor:* Connect the output of the Breaker to the input terminals ( or ) of the Magnetic Contactor.
3. *Contactor to Overload Relay:* Usually, the Overload Relay pins plug directly into the output terminals ( or ) of the Contactor.
4. *Relay to Motor:* Connect the output terminals of the Overload Relay to the motor terminals ().
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3. Control Circuit Wiring
This circuit manages the logic of the starter (Start/Stop/Latching). Assume a 230V AC Coil for this example.
1. *Phase to Overload Relay:* Take one phase from the breaker and connect it to the *NC contact (Normally Closed)* of the Overload Relay (usually terminals **95-96**). This ensures that if the motor trips, the control power is cut.
2. *OLR to Stop Button:* Connect terminal *96* of the OLR to the input of the **Red Stop Button (NC)**.
3. *Stop to Start Button:* Connect the output of the Stop Button to the input of the **Green Start Button (NO)**.
4. *Latching (The "Hold-on" Circuit):* To keep the motor running after you release the Start button, connect an *NO auxiliary contact* of the contactor (usually terminals **13-14**) in parallel with the Start button.
Connect terminal *13* to the input of the Start button.
Connect terminal *14* to the output of the Start button.
5. *Start to Coil:* Connect the output of the Start button to the *A1* terminal of the Contactor Coil.
6. *Neutral to Coil:* Connect the *A2* terminal of the Contactor Coil to the *Neutral* line.
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4. How It Works
*Starting:* When you press the Start button, current flows to the coil (), creating a magnetic field that closes the contactor. The auxiliary contact () also closes, providing an alternative path for the current so the coil remains energized when you release the button.
*Stopping:* Pressing the Stop button (NC) breaks the circuit, the coil loses power, the magnetic field collapses, and the contactor opens.
*Tripping:* If the motor draws too much current, the Overload Relay heats up and opens its NC contact (), cutting power to the control circuit and stopping the motor immediately.
Safety Note
Always ensure the power is *OFF* before wiring.
Double-check that the *Coil Voltage* ( or ) matches your control supply voltage.
Ensure the Overload Relay is set to the *Full Load Amps (FLA)* of the motor.