#protection
7 posts filed under this tag, newest first.
SPD installation: the two wires that decide
An SPD with 2 m of lead passes more than twice the voltage it should. Lead length, Uc and type selection, and how to check a panel you did not build.
7 min read
RCCB keeps tripping: how to find the leakage
Healthy loads leak. Six of them on one board can trip a 30 mA RCCB with nothing faulty anywhere. How to measure the standing leakage and what to change.
8 min read
MCCB keeps tripping: how to find out why
Time the trip first — it halves the search. Then work through overload, short circuit, earth fault and the causes that are not faults at all.
7 min read
DOL, star–delta, soft starter or VFD: how to choose
Inrush is only half the decision. What each starter does to torque, which loads each suits, and the four failure modes that follow the wrong choice.
6 min read
Short-circuit withstand: the cable check everyone skips
A cable that passes current rating and volt drop can still fail under fault. The adiabatic check, the right k value, and why discrimination delays cost copper.
7 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