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Resistance of copper?
12.9 ohms
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Resistance of Aluminum?
21.2 ohms
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Neutral load of a 3-wire feeder supplied by a 4-wire 3-phase 120/208v or 277/480v wye-connected system formula.
Ln= root of ((L1^2 + L2^2) - (L1 x L2))
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In a 230/460v dual-rated motor is what voltage when field windings are connected in series?
Parellel?
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Voltage drop permitted for
-Branch circuit?
-Entire system?
-Feeders?
- branch- 3%
- system- 5%
- feeders- 3%
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order of conducters best to worst?
- silver 105%
- copper 100%
- gold 72%
- aluminum 61%
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Difference between
-Kilowatt (Kw)
-Kilovolt-ampere (Kva)
- Kw = 1000 watts
- indicates the measure of power available for work, indicates real power
- Kva = 1000watts
- indicates the measure of apparent power
- kv=kva when power factor is 1
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single phase standard transformer ratings in kva?
- 1
- 1.5
- 2.0
- 3.05.0
- 7.5
- 10
- 15
- 25
- 37.5
- 50
- 75
100 - 125
- Underlined = also standard 3 phase
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def. branch circuit
The circuit conductors between the final overcurrent device protecting the circuit and the outlets
-
power supplies wired in
-parallel?
-series?
- parallel- Voltage remains the same, current (amp hour for batteries) increases
- series- Voltage is added together, current remains the same
-
Volumes allowence per conductor size?
18, 16, 14, 12, 10, 8, 6
- 18- 1.5 in^3
- 16- 1.75
- 14- 2.00
- 12- 2.25
- 10- 2.5
- 8- 3.00
- 6- 5.00
-
one horsepower = ____watts
746 watts
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When doing a feeder service calculation the load demand factor is?
- 100% for the first 3kva
- 35% 3001va-120,000 va
- 25% 120,001va and up
-
values of AC?
- Instantaneous value- value at any given moment ranging from peak to neg peak
- Peak value- effective value /.707
- - effective value x 1.414
- Effective value- is DC voltage equivalent
- AKA RMS "root mean squared" backwards
-
Volatge drop formula?
VD = (2 x K x D x I)/cm
Voltage drop = 2 x constant x distance x currant / Circular mills
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Resister colors?
- Bad beer rots our young guts but vodka goes well
- black brown red orange yellow green blue violet gray white
-
risister values?
- 1st band - first number
- 2nd band- 2nd number
- 3rd band- multiplie
- 4th band- tolarance 5%-10%
- 5th band- quality
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