Electricity

Quick Links:

Formula Tables

Formula Wheel, Ohms Law Circle, & PIE Circle

Series & Parallel Circuits

Voltage Drop Calculations

MikeHolt_Section01_Electricial Basics

  • Unit 01: Basic Electrical Math and Formulas
  • Unit 02: Electrical Circuits
  • Unit 03: Alternating Current

MikeHolt_Section02_Conductor Sizing and Protection

  • Unit 06: Conductor Sizing and Protection Calculations

MikeHolt_Section03_Raceway, Conductors, and Box sizing

  • Unit 05: Raceway, Conductors, and Box Calculations

MikeHolt_Section04_Motors, Transformers, and HVAC

  • Unit 04: Motors & Transformers
  • Unit 07: Motor and Air Conditioning Calculations

MikeHolt_Section05_Voltage Drop Calculations

  • Unit 08: Voltage Drop Calculations

MikeHolt_Section06_Dwelling Units

  • Unit 09: Dwelling (Single) Unit Calculations
  • Unit 10: Multi-Family Dwelling Calculations

MikeHolt_Section07_Commercial Calcs

  • Unit 11: Commercial Calculations

MikeHolt_Section08_Transformers

  • Unit 12: Transformer Calculations

Definations

Laws

Minnesota Statutes

Character Map & Alt-Codes


NEC Code Book Notes

Important Code Book Sections

Codebook Section Page Description Notes
240.6(A) 70-95 Fuse Sizes
210.52 70-64 Receptacles Dwelling Units
310.15(B)(16) 70-150 Table_Conductor Amps
210.19(A)-Note 4 Voltage Drop
215.2(A)-Note 2 Voltage Drop
210.8 Ground Fault
210.13 Ground Fault
215.10 Ground Fault
240.13 Ground Fault
Overhead Wiring Clearances

Formulas Included

70-147 (& 154) Ambient Temperature Correction
70-149 Conductor Ampacities
70-689 Temperature Change Equation
70-690 Effective Impedance
70-795 I=VA / (E * 1.732)
70-801 Conductor Ampacity
70-806 Availability of System Performance
70-102 Short circuit formulas for conductors
?? Formulas

Ch.9-Tables contain:

  • Raceway Sizing & Bend Radius
  • Conductor Fill & Voltage Drop

Metric Notes

  • KW = 1000 watts
  • KVA = 1000 volt-amps
  • KCMil = 1000 circulr-mills
  • KFt = 1000 feet
  • kVA = Watts / 1000
  • kWh = Watts * Hours / 1000

Equivalences and Acronyms

  • E = V
  • R = (Ohm’s symbol)
  • P = W = VA
  • I = A
  • CEMF = Counter-Electromotive Force = back-EMF = induced voltage = self-inductance
  • Apparent Power = Volt-Amps = VA = Voltage = E

Key People of Electrical History

Michael Faraday (1831)

Heinrich Hertz

Andre-Marie Ampere

Nikola Tesla

Thomas Edison

George? Westinghouse


Internet Resources


Class Notes

Bring Gum, water, snacks to test

Annex D has examples and math calcs – study

  • Multi-Dwelling Units

╧ to earth:

  • limits spikes
  • limits static electricity
  • limits over-current
  1. Grounded = Neutral
  2. Grounding = tied to earth
  3. Ungrounded = hot wire

 

Voltage Drop

  • k = kilo / 1000 / will be given in problem
  • i = current / amps
  • l = length
  • cm = circular mils, Ch.09-Table 08

1 Ø

  • VD = 2kil/ cm
  • CM = 2kil / vd

1 Ø or 3 Ø

  • VD = √3 kil / cm
  • cm = √3 kil / vd

OH/NH = OG/NG

  • Old hot / new hot = old ╧ / new ╧

 

Table 250.66

  • grounding wire
  • earth to panel
  • applies to waterline and building frame

Table 250.102C

  • hot wires

Disregard Ch.’s 1 thru 7 unless referrenced to in Ch. 08NEC Ch. 08

725.3

  • Only those sections of article 300

Continuous duty

  • Considered 3 hours or more

Fuses

  • 80% load if continuous
  • 100% load if non-continuous

Impedence

  • Total opposition to current flow
  • DC circuits
    • resistance
  • AC circuits
    • resistance + impedence
  • Both measured in Ω

Table 110.28

  • Pg 70-50
  • Watertight

Pipe Fill

  • fill nipple to 60% (up to 24″ length)
  • fill conduit to 40% at most

Insulation

  • Pipe fill – Include in calculations
  • Box fill – Do not include in calculations

Use table 4 & 5 to see how much to fill a pipe

Table C1

  • how many of the same cable can get into 1 pipe

Table 5A

  • same size wire but compact

Table 8

  • Circular mils given

Receptacles-Walls

  • 210.52(A)(2)
  • 2′
  • 6′
  • 12′

Receptacles-Kitchen Counters

  • 1′
  • 2′
  • 4′

Interrupting Rating

  • 110.9
  • LEARN THIS!! – unsure the formula – Notes pg 8

250.50

  • Grounding = bare green electrode buried in earth

Use 80% and 125% if need to guess

  • Cu” = box fill
  • Sq” = Pipe fill
  • Pg  10-11, 15, 50, 51, 53-to-61
  • Pg 65-71
  • Pg 97-117

PF = w / va

Eff = Out-Eff / In-Eff

SF (service factor) = ??

Transformer Formula

  • VAP = VAS
  • NP / NS = VP / VS = IS / IP

FD – 2 kil / cmil

CM = 2kil / vd


Questions

  • Power loss in relation to P=IE
  • VAC with Unity Power Factor
  • Difference between a volt-amp and a watt?
  • I = P(E*1.732)
  • Where is Tables 430.3(B)?? Replaced by 450.3(A)  (B), pg 70-333?

To Do

  • Fix Voltage Drop Formulas in table
  • Center Formula Wheel Memorization Tool Table
  • NOTE: Write out Q47, pg 37, MH book
  • add cell borders to series and parallel rule charts
  • Capacitive Reactance is a

 

 

Default Table
Default Table