Level 9 of 33 · Electrical lab
Timers and relays
Level 9 of 33 in the Electrical lab: a free panel wiring exercise at Intermediate level. Use a timer relay three ways: a lamp that comes on after a delay, a lamp that stays on after you switch off, and a flasher built from two timers and a control relay.
Goal
A timer relay changes its contact a set time after its coil is switched on (on-delay) or off (off-delay).
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 24 conductors of the schedule.
- The timers are set to 5 seconds (delay-on and delay-off) and 2 seconds (the flasher timers). Turn the selector S4 to ON and watch.
- 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.
- 24 conductors in the wiring schedule
- 4 dead checks before you touch the panel
Skills
Timers at Intermediate level.
Before you start
Level 8, Star-delta with a timer, comes first. Do it first if the ideas are new to you.
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