Flowchart schematic diagram for the Control Circuit of a Forward Reverse Star Delta or Wye Delta Electric Motor Controller - A how to learn skills training guide for electric motor controller

To help facilitate for a better understanding and further learning and training on the concept of the forward reverse star delta (or wye delta) control (ckt) circuit covered in our previous article, a reversible star delta starter control circuit diagram accompanied with a flowchart diagram is presented below as a follow up learning guide which shows a schematic representation of the sequence of operation for the starting and stopping and running operation of a reversible star delta or wye delta electric motor control circuit in order to provide a visual aid to help diagrammatically visualize how the control circuit flows.

The electrical schematic diagram of a reversible star (wye) delta electric motor control (ckt) circuit:

The parts of the reversible star (wye) delta electric motor control (ckt) circuit includes:

1. Stop push button switch (Normally-Close Contact) - 1 piece
2. Forward push button switch (Normally-Open Contact) - 1 piece
3. Reverse push button switch (Normally-Open Contact) - 1 piece
4. Magnetic contactor coils (for star contactor, forward main contactor, reverse main contactor, forward delta contactor, reverse delta contactor) - 5 units
5. Timer coil - 1 piece
6. Thermal Overload Relay Contact - 1 piece
7. Forward Main Contactor Auxiliary Contact (Normally-Open Contact) - 3 pieces
8. Forward Main Contactor Auxiliary Contact (Normally-Close Contact) - 2 pieces
9. Reverse Main Contactor Auxiliary Contact (Normally-Open Contact) - 3 pieces
10. Reverse Main Contactor Auxiliary Contact (Normally-Close Contact) - 2 pieces
11. Star Contactor Contact (Normally-Close Contact) - 1 piece
12. Timer Contact (Normally-Open Contact) - 1 piece
13. Timer Contact (Normally-Close Contact) - 1 piece

The flowchart diagram of the star (wye) delta electric motor control (ckt) circuit:
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Procedural sequence to learn about the method of operation of the star (wye) delta electric motor control (ckt) circuit:

1. RUN MODE: Depending on the choice of the motor rotational direction, the operator presses the forward or the reverse push button switch. With the stop push button switch and the thermal overload contact remained close at OFF state, then power flows down to the selected forward or reverse main contactor coil.
2. When any of the forward or the reverse main contactor coil is energized, its auxiliary contact connected in parallel across the forward or reverse push button switches closes which serves as a holding contact to maintain the forward or the reverse main contactor coil energized after the operator releases his finger from any of the push button switches.
3. While the normally-close contact of the timer is yet inactive at close state, and with the forward or the reverse main contactor coil energized, and with another normally-open contact of either the forward or the reverse main contactor now at close state, power is then permitted to flow to the star contactor coil and the timer coil, thereby placing the motor terminal connected in star configuration.
4. With the timer coil activated, the timer starts to count up until it reaches its specified time period. Once the elapse time is up, the normal state of the timer contacts changes state from close to open and from open to close.
5. The elapsed time will open a timer contact to remove power flow to the star contactor coil thereby releasing the motor from star configuration, while at the same time another timer contact will close to permit power flow to either the forward or reverse delta contactor coil to reconfigure the motor terminal to a delta connection.
6. During the initial start sequence wherein the star contactor coil is active, its auxiliary normally-close contact is opened to prevent power flow to both the forward and the reverse delta contactor coils. And then when the control circuit switches to the delta mode with the activation of the timer, the auxiliary contact from any one of the energized forward or reverse delta contactor coils would also be opened to prevent power flow to the star contactor coil. These interlock contacts that are each connected in opposite order to the star and delta contactor coils are intended to prevent the simultaneous activation of both star and delta contactor coils.
7. During the final run sequence of the circuit wherein the control switches from star to delta mode, interlock contacts from both forward and reverse main contactors are placed on opposite sides of both forward and reverse delta contactor coils, that is, when the forward command is active then the forward interlock contact placed before the reverse delta coil will be open to prevent power flow to the reverse delta coil, likewise, when the reverse command is active then the reverse interlock contact placed before the forward delta coil will also be open to prevent power flow to the forward delta coil.
8. STOP MODE: Operator presses the stop push button switch. This action disconnects the control circuit from the power source which prevents power flow to all energized contactor coils including the timer coil as a result of the opening of the normally-close contact of the OFF push button switch.
9. CIRCUIT INTERRUPTION: The thermal overload relay detects motor overload current, which when detected will activate the thermal switch to open its normally-close contact to isolate power flow to all energized coils in the circuit, thus, deactivating the control (ckt) circuit.

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