Level 7 of 33 · Electrical lab
Forward and reverse with an interlock
Level 7 of 33 in the Electrical lab: a free panel wiring exercise at Intermediate level. Reverse a motor by swapping two phases on a second contactor, and make it impossible for both contactors to pull in together: each one's normally closed auxiliary contact sits in the other's coil path.
Goal
To reverse a three-phase motor you swap any two of its phases.
What you do
- Lock out the board at the isolator Q1: switch OFF, apply your lock and your tag.
- Prove it dead, live-dead-live: prove the meter on the proving unit, check the board reads 0 V, prove it again.
- Wire the 23 conductors of the schedule.
- Check the phase swap with the meter and a phase rotation indicator before you restore power: K2 puts L3 where L2 was.
- Last. Restore power (tick the checklist, remove your tag and lock, switch Q1 ON), try every button, then run the FAT.
Done when
The factory acceptance test is marked against the panel you built.
- 23 conductors in the wiring schedule
- 4 dead checks before you touch the panel
Skills
Motor starters at Intermediate level.
Before you start
Level 6, Direct-on-line motor starter, comes first. Do it first if the ideas are new to you.
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