ELECTRICAL TOOLBOX

Power conversions — kW ⇄ kVA ⇄ Amps · 1-phase & 3-phase · LV & primary voltages

system

line-to-line volts

power factor

kW (real)

kVA (apparent)

amps

—

kVA

—

wire basis (×1.25)

—

kVAR @ PF

—

transformer full-load current

kVA

system

primary volts

secondary volts

primary FLC

—

secondary FLC

—

turns ratio

—

std 1-ph kVA: 10 · 15 · 25 · 37.5 · 50 · 75 · 100 · 167 · 250 · 333 · 500 | std 3-ph kVA: 15 · 30 · 45 · 75 · 112.5 · 150 · 225 · 300 · 500 · 750 · 1000 · 1500 · 2000

motor quick table — NEC 430.250, 460 V · 3-ph induction

230 V ≈ ×2 · 575 V ≈ ×0.8 · 1 HP = 746 W

Power wire selector — ≤600 V · NEC 75 °C copper · OCPD · EGC · voltage drop

system

volts

load amps

one-way length ft

max voltage drop

continuous load

wire size (Cu)

—

ampacity 75 °C

—

breaker / fuse

—

ground (EGC)

—

voltage drop

—

sized by

—

size	ampacity	OCPD	EGC	drop V	drop %

Ampacities: NEC 310.16, 75 °C Cu, 30 °C ambient, up to 3 current-carrying conductors — derate for more. Small-conductor OCPD caps per 240.4(D): 14→15 A · 12→20 A · 10→30 A. Effective Z from Ch.9 Table 9 (Cu, PVC conduit, 0.85 PF). EGC per 250.122.

above 600 V — MV quick reference

5 kV class → 2.4 / 4.16 kV systems · 8 kV → 7.2 kV · 15 kV → 13.2 / 13.8 / 14.4 kV · 25 kV → 24.94 kV · 35 kV → 34.5 kV (L-L)
Typical: EPR/XLPE insulation, 133%/100% insulation level, copper, shielded, in concrete-encased duct or direct burial (jacketed). Terminations: load-break elbows (deadfront) or potheads — only with proper MV training/PPE. Min bending radius ≈ 8–12× D. Sizing must follow the manufacturer's ampacity table (duct bank grouping, soil RHO, loading depth) — never a web tool alone.

Low voltage selector — 12 / 24 / 48 V AC & DC · voltage-drop limited

system

load amps

≈ load VA / W

one-way length ft

max drop

wire size (Cu)

—

voltage drop

—

delivered

—

max length (this size)

—

ft (1-way)

Round-trip path counts twice (2× length). DC resistance from NEC Ch.9 Table 8 (Cu @ 20 °C). 24 VAC: transformer VA is the budget — keep total ≤ nameplate. Class 2 wiring methods per NEC 725.

Signal & communications — cable selector · RS-485 / MS-TP · Cat · 4–20 mA · coax

application

RS-485 segment length guidance (18 AWG, 120 Ω cable)

baud	9600	19200	38400	76800	115200
typical max ft	4000	3300	2600	1600	1200

baud

9600

19200

38400

76800

115200

typical max ft

4000

3300

2600

1600

1200

Termination 120 Ω at both physical ends only · daisy-chain topology (no stars/taps) · shield grounded at one end · ≤ ~120 devices/segment.

cable jacket ratings

CMP plenum (risers/plenums) · CMR riser · CM general purpose · CMX residential/dwelling · outdoor/direct burial = flooded jacket. Plenum where air-handling — always local code first.

Power conversions — kW ⇄ kVA ⇄ Amps · 1-phase & 3-phase · LV & primary voltages

transformer full-load current

motor quick table — NEC 430.250, 460 V · 3-ph induction

Power wire selector — ≤600 V · NEC 75 °C copper · OCPD · EGC · voltage drop

above 600 V — MV quick reference

Low voltage selector — 12 / 24 / 48 V AC & DC · voltage-drop limited

Signal & communications — cable selector · RS-485 / MS-TP · Cat · 4–20 mA · coax

4–20 mA loop budget

RS-485 segment length guidance (18 AWG, 120 Ω cable)

cable jacket ratings