Level 3 · Free project

Commission the star-delta fan starter

Start an 11 kW exhaust fan in star to hold the starting current down, then change over to delta. Main, star and delta contactors, a hardwired interlock and a timed changeover.

Free with a free account. Runs in your browser.

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The circuit diagram of the panel, as drawn in the lab: Commission the star-delta fan starter
The closed cabinet door with its lamps, buttons and isolator handle, as drawn in the lab: Commission the star-delta fan starter

What you will build

Work order WO-PS-301. Your site team, Commission the star-delta fan starter.

Kaveri Textiles, Coimbatore. Exhaust fan EF-301 is driven by an 11 kW, 415 V motor (delta, 21 A) with six terminals. A direct start would draw about six times full-load current for the first second, so the motor is started in star, which cuts the starting current to a third, and then changed over to delta. The starter panel +F301 has arrived with its power circuit and 24 V supply wired. The control wiring to the PLC is yours.

What you will learn

  • Lock out and prove dead, live then dead then live
  • Land 25 control conductors from a wiring schedule
  • Read the supplied PLC program and match it to your wiring
  • Restore power safely, test, and run the FAT

How it goes

  1. Lock out the panel at the main isolator Q1: switch OFF, apply your lock and your tag.
  2. Prove it dead with the meter, live-dead-live.
  3. Wire the 25 conductors of the wiring schedule. Check the two interlock links: K2's coil goes through K3's NC contact, and K3's coil through K2's. K2 and K3 must never be in together: they would short two phases through the motor.
  4. Read the supplied PLC program: K1 for the whole run, K2 for the first 5 s, a 0.1 s dead time, then K3. The overload F3 is set to 12.2 A, which is 0.58 times the motor's 21 A, because in this starter it carries the winding current.
  5. Restore power: tick the checklist, remove your tag and lock, switch Q1 ON, put the PLC in RUN.
  6. Test: START starts in star and changes over to delta, STOP and the E-STOP stop the fan, and an overload trip stops it and lights TRIP. Then run the FAT.

Parts in the panel

  • Main isolator, 4-pole, 63 A

    Switches all three phases and neutral. The incoming cable lands on 1, 3, 5, 7: those terminals stay live when it is OFF.

  • MCB 2-pole, 6 A, C curve: control supply

    Feeds the 24 V power supply with 230 V (L1 and N).

  • MCB 3-pole, 32 A, D curve: motor circuit

    Protects the motor circuit against short circuits. The overload relay protects the motor against overload.

  • Main contactor 3-pole, 25 A AC-3, coil 24 V DC, 1 NO aux

    Connects the motor to the supply for the whole run, in star and then in delta. Its 13-14 auxiliary tells the PLC it really pulled in.

  • Star contactor 3-pole, 18 A AC-3, coil 24 V DC, 1 NC aux

    Ties the winding ends U2, V2, W2 together (the star point). Mechanically interlocked with K3. Its NC 21-22 is in K3's coil circuit.

  • Delta contactor 3-pole, 25 A AC-3, coil 24 V DC, 1 NC aux

    Closes the delta: U1-W2, V1-U2, W1-V2. Mechanically interlocked with K2. Its NC 21-22 is in K2's coil circuit.

  • Thermal overload relay, 10-16 A, set 12.2 A

    Set to 0.58 × the motor's 21 A, because in a star-delta starter the overload carries the winding current, not the line current. 95-96 (NC) opens and 97-98 (NO) closes on a trip.

  • Power supply 230 V AC to 24 V DC, 5 A

    Its 0 V (−) is bonded to PE at the factory, so 0 V and earth are the same potential.

  • PLC: compact CPU, 8 DI / 6 DQ, 24 V DC

    Inputs I0.0-I0.7 are PNP: 24 V on the terminal turns the input on, with 1M at 0 V. Outputs Q0.0-Q0.5 source 24 V from 3L+.

  • Terminal strip X2: 24 V DC distribution

    Positions 1-6 are bridged +24 V, 7-12 are bridged 0 V. Top and bottom of each position are the same point.

  • Terminal strip X1: motor, six winding ends

    The six winding ends of the motor land here: U1 V1 W1 and U2 V2 W2, plus earth.

  • PE bar

    Protective earth, bonded to the incoming supply's earth.

  • Push button START, green, 1 NO

  • Push button STOP, red, 1 NC

  • Emergency stop, 2 NC, twist to release

    Contact 11-12 is hardwired in the coil circuit; 21-22 tells the PLC.

  • Pilot lamp green 24 V: RUNNING

  • Pilot lamp amber 24 V: OVERLOAD TRIPPED

  • Motor 3-phase 11 kW, 415 V delta, 21 A, six terminals, driving exhaust fan EF-301

Questions

Is it free?
Yes. The lab is free to use with a free account. There is nothing to buy to open this scenario.
Do I need to install anything?
No. It runs in your browser with a 3D panel, a circuit drawing, a meter and a PLC.
What will I do in Panel Lab 3?
You wire a control panel, then check your work against an acceptance test.
How long does it take?
Plan for one sitting. You can stop and come back.
Do I need experience?
No. Each work order says what to do step by step, and hints are there if you get stuck.
Open in the lab