Flashcard · Electrical Theory and Calculations
Three-phase current from VA?
I = VA ÷ (1.732 × line-to-line volts).
Electrical theory: three-phase power
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- Three-phase current from VA?
- I = VA ÷ (1.732 × line-to-line volts).Electrical theory: three-phase power
- Handy products: 1.732 × 208, × 240 and × 480?
- 360.3, 415.7 and 831.4.Electrical theory: three-phase power
- kVA from kW and power factor?
- kVA = kW ÷ PF. kVA is always the larger number.Electrical theory: power factor
- What does raising power factor do to line current for the same kW?
- Lowers it. New current = old current × old PF ÷ new PF.Electrical theory: power factor correction
- Single-phase voltage drop formula (circular mil method)?
- VD = 2 × K × I × L ÷ CM, with L the one-way length.Electrical theory: voltage drop
- Three-phase voltage drop formula?
- VD = 1.732 × K × I × L ÷ CM.Electrical theory: voltage drop
- K for copper and for aluminum?
- About 12.9 for copper and 21.2 for aluminum, trade approximations rather than NEC values.Electrical theory: voltage drop
- Sizing a conductor for drop: which formula?
- CM = 2 × K × I × L ÷ VD (single-phase) or 1.732 × K × I × L ÷ VD (three-phase), then pick the first size at or above it.Electrical theory: voltage drop; NEC 2023 Chapter 9
- Where do conductor areas in circular mils come from?
- The conductor properties table in Chapter 9.NEC 2023 Chapter 9
- Are 3% and 5% voltage drop NEC requirements?
- Not for general circuits. They are recommendations in informational notes in Articles 210 and 215.NEC 2023 Articles 210 and 215 (informational notes)
- Transformer full-load current, three-phase?
- I = kVA × 1,000 ÷ (1.732 × V), at the voltage of the side you want.Electrical theory: transformer current
- Maximum fault current at a transformer secondary (infinite primary)?
- Full-load current × 100 ÷ %Z, the same as dividing by %Z as a decimal.Electrical theory: short-circuit current