ELECTRICAL DISTRIBUTION:

Dimmer Systems may be permanent or temporary.
Some understanding of power distribution is necessary if you ever 
need to do a hook-up.
BUT
This lecture does not mean you will be qualified to DO IT!
Electricity is not complicated, but it CAN BE dangerous.

Electric Distribution Systems
USA standard line voltage of 120 v., 60 Hz. 
Quite different elsewhere in the world. 

Direct Current: Earliest power systems (Edison's) were DC.
Simple to make and use, but wouldn't reach over great distances.

Alternating Current system: Universal now:
Generated at power plants as very high voltage 3 phase Delta.
    -Three coils arranged around a core, spun by steam, water, wind, etc.
    -Phases are 120 degrees shifted in phase from each other.
    -Carried cross-country and transformed into several schemes:

Delta Service
Three-phase: 3 hots, no neutral.
208 v. between Hots, 120 v. to Ground, but NO NEUTRAL.
Used mostly to run three phase motors.

Wye Service:
Also Three phase, an adaptation of Delta
Three Hots, one Neutral,  120 volts any Hot to Neutral or Ground.
•Three phases 120 degrees out of phase w/ next, 208 v. Hot-to-Hot, 
   120 v. Hot-to-Neutral.
•This system used in most industries, inc. Theatre.
•Can be used as three single-phase or one three-phase lines.

Single phase 240:
most modern residences, older theatres.
Taken as secondary to one coil of 3 phase supply tranformer.
•Neutral derived as center tap of coil.
•Either hot-to-neutral = 120 volts   Hot-to-Hot = 240 v.

Single phase 120:
Standard wall outlet.
One hot and one neutral, which is grounded at the entrance panel.

AN IMPORTANT NOTE ABOUT GROUNDING!:
 Grounding conductor which isn't supposed to carry current.

Neutral and Ground are bonded ONLY ONCE- at the Service Entrance.

Theatres come as Wye, ocassionally split Single phase.
Dimmers must be wired in to match service available.  
    Some care needed to balance phases.
Some industry uses 480 v. systems, but of no use in theatre. balance phases.

Making a hook-up:
Portable dimmers connected at the Company Switch or Bull Switch
Five lugs for each hook-up, Ground, Neutral, 3 Hots
   Neutral and ground NEVER connected at Bull, only at service entrance.

RULES of HOOKUPS:
   •Make SURE power is disconnected
   •Attach tails in right order with right colors: 
    Ground/ green Neutral/ white or grey Hots/ Black, Red. Blue 
    Orange may be used, but really for something else
   •Meter tails before connecting board.
   •Always CONNECT feeder in proper order.

FEEDER cable is usually:
   •4/0 cable, good for up to 400 amps.
   •2/0, good up to 195 amps.
Feeder usually uses Cam-loks, not legal in most other industries.

Important to hook up properly.  NOTE REPETITION!
1.  Ground/ green 2.  Neutral/ white or grey 3-5.  Hots/ Black, Red. Blue


©2000, Mick Alderson