Flowchart guide for the Control Circuit of a Direct On Line DOL Electric Motor Controller - A how to do guide for electric motor controller

To help facilitate for a better understanding of the concept of the Direct On Line (DOL) control circuit covered in our previous article, a flowchart diagram is presented below as a follow up guide which shows a schematic representation of the sequence of operation for the start stop and run operation of the DOL electric motor controller control circuit in order to provide a visual aid to help diagrammatically visualize how the control circuit flows.

The electrical schematic diagram of the DOL electric motor control circuit:

The parts of the DOL electric motor control circuit includes:

1. Stop Push Button Switch (Normally-Close Contact) - 1 Piece
2. Run Push Button Switch (Normally-Open Contact) - 1 Piece
3. Thermal Overload Relay (Normally-Close Contact) - 1 Piece
4. Main Contactor Coil - 1 Piece
5. Main Contactor Auxiliary Contact (Normally-Open Contact) - 1 Piece 
   

The flowchart diagram of the DOL electric motor control circuit:

Procedural sequence for the method of operation of the DOL electric motor control circuit:

1. RUN MODE: Operator presses the run push button switch. If the stop push button switch and the thermal overload contact remains close at OFF state, then current flows down to the main contactor coil.
2. When the main contactor coil is energized, its auxiliary contact connected in parallel across the run push button switch closes which serves as a holding contact to maintain the main contactor coil energized after the operator releases his finger from the run push button switch.
3. STOP MODE: Operator presses the stop push button switch. This action disconnects the control circuit which prevents current flow to the main contactor coil as a result of the opening of the normally-close contact of the stop push button switch.
4. CIRCUIT INTERRUPTION: The thermal overload relay detects motor overload current which in turn activates the thermal switch to open its normally-close contact to isolate current flow to the main contactor coil, thus, deactivating the control circuit.
   

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