#design
13 posts filed under this tag, newest first.
How many solar panels for 1000 units a month?
The arithmetic from your bill to a panel count and a roof area, why the annual average misleads, and the four things that decide whether you actually get it.
6 min read
The power factor penalty: what it costs, what fixing returns
Where reactive power comes from, how Indian tariffs charge for it, and a worked payback on a 200 kW plant — where the penalty is the smaller of the two savings.
6 min read
DG set sizing: why motor starting usually governs
Two calculations decide a generator rating and most quotations do only one. A worked example where the starter choice halves the frame size.
7 min read
IP ratings for panels: what IP54, IP65 and IP66 survive
What each digit is tested against, why a higher rating derates your busbars, and the condensation problem that ruins sealed outdoor enclosures.
8 min read
Copper or aluminium: where aluminium stops being cheaper
Aluminium needs 1.6 times the cross-section for the same current — and still costs less per metre. The crossover, and the four places it goes wrong.
8 min read
Sizing a distribution transformer: kVA, %Z and fault level
Size a distribution transformer from maximum demand, not connected load — and why the per cent impedance on the nameplate is what decides your switchgear.
10 min read
Connected load, maximum demand and diversity factor
The three numbers get used as though they were one. Which to size on, typical demand factors by load type, and what getting it wrong costs on the bill.
7 min read
How to read a cable datasheet without getting caught out
Reference conditions, two rating columns, mV/A/m versus ohms per km, one-second fault ratings and how to decode A2XFY — the fine print that decides the size.
7 min read
Cable derating factors: the complete table
Ambient, grouping and installation factors in one place, worked through — plus the four factors that are not in any table but still apply.
11 min read
Motor full load current at 415 V: the chart, and the caveats
Full load current for standard three-phase motors from 0.75 to 160 kW, with contactor, relay and cable figures — and why the nameplate rarely matches the table.
9 min read
MCB, MCCB, ACB and RCCB: what each protects, and where
The four devices compared on rating, breaking capacity and adjustability — plus trip curves, Icu versus Ics, and choosing an RCD type for VFD circuits.
7 min read
Voltage drop limits: why lighting gets 3 % and power 5 %
What IS 732 actually permits, where the two limits come from, and why the same cable can pass for a motor and fail for a lighting board on the same site.
7 min read
How to size a cable correctly: the six-step sequence
Design current, derating, tabulated rating, breaker coordination, volt drop and short-circuit withstand — the full sequence, worked through for a 45 kW motor.
8 min read