Stage Electrics 234-236 Possible Quiz Questions

Note that I may ask some questions that are not on this list!!  Please do not assume that these are the only possible questions!!

DEP235
Quiz 1
Quiz 2

Mid-Term
Quiz 3

Final

DEP236
Quiz 1
Quiz 2
Quiz 3
Quiz 4

DEP235 First Quiz - class #4

1. Use W=VA and P=IE and know what they mean
   1. W=Watts, V=Volts, A=Amps, P=Power (Watts), I=Intensity (Amps), E=Energy (Volts).
   2. 120v X 20a = 2400W
2. Because of P=IE, 2.4Kw dimmers are only good for 2.4Kw when they have a full 120v.  As the voltage is lower so is the actual ability for the dimmer to output wattage.  The dimmer has a breaker rated for 20 amps, therefore if the voltage is 117v then a "2.4Kw dimmer" can only output 2340w, because that equals 117v X 20a
3. Amperage capacity is related directly to how large the wire is: 12 gauge wire can handle more amperage than 14 gauge wire.
4. How to identify different types of power and make certain you have the type you want.
   1. Single phase power uses a neutral, ground and one or two hots.  You would find: 120v between any hot and neutral or hot and ground; 220v between the two hots (if there are two) and zero between neutral and ground (if the service is wired correctly).
   2. Three phase power uses three hots and...
      1. Delta would have a ground.  Delta power should have an orange wire in the mix, but to make certain, power should always be METERED.  You would find: 208v (or similar) between the "high" leg and the ground; 125v between either of the two "low" legs and ground; 240v between any two "hots."  Delta, strictly speaking does not require the neutral to work, this could be another clue - if your tie-in panel is missing the neutral (the white one), it could be Delta - stay away!
      2. Three-phase "Y" would have a ground and a neutral.  Three phase "Y" power provides the type electricity typically used by theatrical dimmer racks.  This is the 120/208v variety.
5. Rule of Thumb amperage ratings - pretty much the chart in table 400.5 of the code.
6. NEC520 governs the use of electricity in theaters.  It is good to know NEC400.

*As far as I know there are no cables in theater larger than #2, therefore the "Rule of Thumb" chart moves from table 400.5a (cables) in the code to 400.5b (single wire) and assumes the use of feeder cable (SC or SCE cable rated at 90º) that is NOT banded together.  Once feeder is banded the rating is reduced by 75%!

6. The standard wiring of 6-circuit cables using Socapex compatible connectors is:

   CIRCUIT NUMBER	HOT	NEUTRAL	GROUND
   Circuit 1	pin 1	pin 2	pin 13
   Circuit 2	pin 3	pin 4	pin 14
   Circuit 3	pin 5	pin 6	pin 15
   Circuit 4	pin 7	pin 8	pin 16
   Circuit 5	pin 9	pin 10	pin 17
   Circuit 6	pin 11	pin 12	pin 18

     Pin 19 is a "special pin sometimes used for shield."

    

7. Color coding is used when wiring buildings to help indicate which wire does what.  The colors can be wrong!  Always meter power!  Conventional colors mean:
   1. Black - either "A" phase in 3-phase or a "hot" in single phase.
   2. Blue - "C" phase of a 3-phase circuit.
   3. Green or Green with yellow stripe - Ground
   4. Orange - Probably a "hot" in Delta 3-phase - make sure you meter power!
   5. Red - "B" phase of a 3-phase circuit.
   6. White or Gray - Neutral
   7. Any hot with a white stripe is often a "switch-leg." Ask me about it sometime.