| Common Electrical Terms, Formulas and Charts |
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Below are some commonly used electrical reference items.
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Common Electrical Terms Simplified
- Ampere - rate of flow of current
- Kilovolt Ampere - one kilovolt ampere - KVA - is equal to 1,000 volt amperes
- Kilowatt- Unit of power - KW - equal to 1000 watts
- Ohm - unit of resistance
- Power Factor - ratio of watts to volt amperes
- Volt - unit of electrical potential or motive force
- Volt Ampere - product of volts and amperes as shown by a voltmeter/ammeter
- Watt - unit of electrical energy or power
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Portable Cord Letter Connotations
- S = 600 Volt Service Cord
- J = Junior Service - 300 Volt
- T = Thermoplastic
- E = Elastomer - thermoplastic that looks and feels like rubber
- O = Oil Resistant Outer Jacket
- OO = Oil Resistant Outer Jacket and Oil Resistant Insulation
- W = CSA Weather and Water Resistant (approved for indoor and outdoor use)
- SPT-1 = All thermoplastic construction, parallel jacketed. 300 Volt (18 gauge)
- SPT-2 = Same as SPT-1, but with heavier construction (18-16 gauge)
- SPT-3 = Same as SPT-2, but with heavier construction (18-10 gauge)
- SRDT = Portable dryer or range cord, parallel jacketed. 300 Volt
- HPN = Two-conductor, neoprene insulated heater cord. Parallel construction, damp location. 300 Volt
Example: 12-3 SJOW = 12 Gauge, 3 Conductor, Service Junior 300 Volt, Oil and Weather resistant
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Common Electrical Formulas, NEMA Charts & Definitions
KW = Kilowatts
KVA = kilovolt/amperes
HP = horsepower
% Eff. = percent efficiency
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To Find
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Single Phase
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Amps
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Amps = Watts ÷ Voltage
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Watts
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Watts = Amps x Voltage
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Voltage
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Voltage = Watts ÷ Amps
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To Find
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Three Phase
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Amps
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Amps = Watts ÷ Voltage ÷ 1.73
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Watts
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Voltage x Amps x 1.73
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To Find
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Single Phase
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AMPERES when KVA is known
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KVA X 1000
Volts
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AMPERES when horsepower is known
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HP X 746
Volts X % Eff.X Power Factor
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AMPERES when kilowatts are known
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KW X 1000
Volts X Power Factor
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KILOWATTS
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Amps X Volts X Power Factor
1000
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KILOVOLT/
AMPERES
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Amps X Volts
1000
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HORSEPOWER
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Amps X Volts X % Eff. X Power Factor
746
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WATTS
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Volts X Amps X Power Factor
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If power factor is unknown, multiply by 1, use result as a guide.
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To Find
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Three Phase
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AMPERES when KVA is known
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KVA X 1000
Volts X 1.73
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AMPERES when horsepower is known
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HP X 746
Volts X 1.73 X % Eff. X Power Factor
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AMPERES when kilowatts are known
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KW X 1000
Volts X 1.73 X Power Factor
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KILOWATTS
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Amps X Volts X 1.73 X Power Factor
1000
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KILOVOLT/
AMPERES
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Amps X Volts X 1.73
1000
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HORSEPOWER
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Amps X Volts X 1.73 X % Eff. X Power Factor
746
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WATTS
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Volts X Amps X 1.73 X Power Factor
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If power factor is unknown, multiply by 1, use result as a guide
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To Find
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Direct Current
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AMPERES when horsepower is known
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HP X 746
Volts X % Eff.
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AMPERES when kilowatts are known
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KW X 1000
Volts
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KILOWATTS
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Amps X Volts
1000
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HORSEPOWER
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Amps X Volts X % Eff.
746
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WATTS
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Volts X Amps
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NEMA Enclosure
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Definition
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Type 1
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Indoor use, limited protection
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Type 2
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Indoor use, greater protection against water and debris
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Type 3
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Outdoor use, limited protection
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Type 3R
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Outdoor use, greater protection against water, debris and ice
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Type 4
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Indoor or outdoor use, greater protection against hose directed water, debris and ice
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Type 4X
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Same as Type 4, corrosion resistant (normally Stainless Steel)
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Type 6
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Same as Type 4, with temporary protection from limited submersion
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Overcurrent protection for conductor types marked (*) shall not exceed 15 amperes for No. 14, 20 amperes for No. 12, and 30 amperes for No. 10 copper. See NEC 240-2 for motor & welders overcurrent protection exceptions. See NEC 240-3D.
For ambient temperatures other than those noted above, see NEC tables 310-16 & 310-18 Footnotes.
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Disclaimer
This material is presented as a guide only. A-Line Electrical Supply, Inc. assumes no responsibility for any information or results from the use of such information. The results produced by these calculators and general information are not guaranteed to be correct or applicable in any or all situations. The user must have a thorough understanding this trade and any applicable Electrical Codes where work is being performed. It is the users responsibility to verify compliance with local jurisdictions.
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