Electrical & Engineering4 min read
Solar Panel Sizing: How Many kW Do You Need?
20 kWh a day, 5 peak-sun hours and 80% system efficiency means a 5 kW array, or about 10 panels of 540 W. See the formula and the checks before you buy.
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- Electrical & Engineering5 min read
Three-Phase Apparent Power: the √3 Formula
Three-phase apparent power in kVA = √3 × line voltage × line current ÷ 1,000. At 400 V and 25 A, a balanced load is about 17.32 kVA.
- Electrical & Engineering5 min read
Transformer kVA: Apparent Power from Volts and Amps
Single-phase apparent power in kVA = volts × amps ÷ 1,000. At 230 V and 20 A the load is 4.6 kVA, which is 92% of a 5 kVA transformer.
- Electrical & Engineering4 min read
UPS Size and Backup Time From Battery Wh
A 310 W desk setup needs about 517 VA on a 0.6 power-factor UPS, and a 12 V 100 Ah battery then keeps it up for around 2.6 hours. Here is how to size both.
- Electrical & Engineering5 min read
Voltage Drop in a Cable: Formula and Example
A 2.5 mm² copper cable carrying 10 A over 20 m loses about 2.75 V, using ΔV = 2 × I × ρ × L ÷ A. Here is how to check, limit and fix the loss.
- Electrical & Engineering5 min read
Choosing a Wire Gauge: Current, Length and Voltage
Wire size depends on current rating, run length and voltage drop. For 15 A over 20 m at 230 V, 2.5 mm² drops about 1.8%; on 12 V you need far more.
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