Guides and notes on industrial electrical and automation parts: selection, wiring, settings and ordering.
The Ib ≤ In ≤ Iz cable coordination rule under IEC 60364-4-43, why the second condition on conventional tripping current collapses for MCBs, and the fire-risk consequence of getting In...
10 min read
A step-by-step checklist for selecting RCD sensitivity, type, poles and rated current, matched to the earthing system, IEC standards, and special cases like EV chargers and VFDs.
11 min read
Fixed, plug-in, and withdrawable MCCB construction compared: isolation, downtime, cost, and where each fits on ABB, Schneider, and Siemens frames.
10 min read
PTC thermistor and PT100/PT1000 RTD temperature monitoring relays compared: trip thresholds, hysteresis, wiring and where each type is specified for motor and bearing protection.
10 min read
How to size VFD motor cable for both ampacity and PWM reflected-wave voltage, and when cable length forces a dV/dt reactor or sine-wave filter.
9 min read
How manual (HAND) and automatic reset differ on thermal overload relays, when each is safe, and how trip class affects cool-down time before reset.
10 min read
How to size a soft starter for a high-inertia load: the torque-vs-voltage sizing trap, WK² acceleration time, current limit versus torque control, and AC-53a duty-rating checks.
11 min read
MPCB and fuse-plus-overload-relay motor protection schemes compared on short-circuit clearing, overload accuracy, coordination type, reset time, and installed cost.
10 min read
A load-by-load walkthrough matching MCB tripping curves B, C, D, K, and Z to inrush current so the breaker neither nuisance-trips nor under-protects the circuit.
10 min read
Why RCDs false-trip from cumulative leakage and transients, and how super-immunized (SI) devices, S-type units, and circuit splitting each solve a different cause.
9 min read
Icu certifies a safe trip; Ics certifies the MCCB is still fit for service afterward — this article breaks down how IEC 60947-2 defines all three ratings and why Icw...
8 min read
How conductive level monitoring relays detect liquid presence, size sensitivity for the medium, and control pump up/down cycles with dry-run protection.
8 min read
A practical guide to VFD parameter setup: motor nameplate data, control mode selection, ramp times, I/O assignment and protection settings for correct first-time commissioning.
10 min read
The compensating bimetal cancels ambient-driven drift in a thermal overload relay so the trip point tracks motor current, not panel temperature.
9 min read
How to read the AC-53a/AC-53b duty code, size the current ratio against FLC, and account for starts-per-hour so a soft starter does not trip on its rated duty.
8 min read
How to size an MPCB's short-circuit breaking capacity (Icu) against the panel's prospective fault current, the Icu-vs-Ics distinction, and when back-up protection with an upstream device is required.
10 min read
How to size an MCB using the Ib ≤ In ≤ Iz coordination rule, curve matching, and breaking-capacity verification, with a worked example.
9 min read
How TT, TN and IT earthing systems change RCD requirements, loop-impedance sizing and where the insulation monitoring device takes over.
11 min read
How thermal-magnetic and electronic MCCB trip units sense overload and short-circuit, what each lets you adjust, and where each fits by application.
11 min read
How overcurrent and undercurrent monitoring relays sense load current, set thresholds, and catch jams, broken belts, and dry-running pumps that a motor breaker alone cannot see.
8 min read
The affinity laws show why cutting a centrifugal pump or fan's speed 20% can cut its power draw nearly in half, and where that cube-law estimate breaks down in real...
9 min read
How overload relays detect a lost or unbalanced phase and trip before single-phasing overheats the two remaining motor windings.
9 min read
How to size a soft starter correctly by full-load current, IEC 60947-4-2 duty class, starting torque against the load, control method, wiring topology and protection features.
10 min read
How MPCBs detect single-phasing and why differential phase-loss tripping reacts faster than a plain bimetal thermal element.
9 min read
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