Commission the star-delta fan starter

The brief

Work order

WO-PS-301

Job

Commission the star-delta fan starter

Difficulty

Intermediate

Type of work

Commissioning

Detail

25 wires, lockout, meter checks and a PLC program

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 do

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.

What the test checks

The factory acceptance test is marked against the panel you built. The level sets out:

• 25 conductors in the wiring schedule
• 6 dead checks before you touch the panel

In this lab

• Lock out and prove dead, live-dead-live
• Wire the backplate from the schematic
• Meter, tester, clamp and insulation tester