MCB Derating for Temperature and Grouping
How ambient temperature and enclosure grouping reduce an MCB's effective continuous current below its nameplate In, with the IEC 60898-1 basis and a worked 50C example.
9 min read
Technical
Technical for buyers and panel builders
Guides and notes on industrial electrical and automation parts: selection, wiring, settings and ordering.
- Articles
- 542
RCD for Solar PV: Why Type B Is Required
Transformerless solar PV inverters can blind Type AC and Type A RCDs with smooth DC fault current, which is why IEC 60364-7-712 and most inverter manuals require a Type B...
10 min read
How to Set MCCB Trip Settings (Ir, Isd, Ii)
How to derive Ir, Isd/tsd, and Ii settings on an MCCB electronic trip unit for correct overload protection and breaker selectivity.
11 min read
How to Select a Phase and Voltage Monitoring Relay
A step-by-step selection guide for phase and voltage monitoring relays, covering function match, auxiliary supply, threshold setting, output logic, and Schneider vs ABB CM comparison.
9 min read
ABB ACS Drives: Full Range Review (ACS180 to ACS880)
A working comparison of ABB's ACS drive lineup, from the entry ACS180 machinery drive to the ACS880 industrial DTC flagship, plus the ACH580 and ACQ580 application variants.
9 min read
How to Select and Set a Thermal Overload Relay for a Motor
A step-by-step guide to reading motor nameplate FLC, matching relay range and frame, setting the dial, and picking the trip class for a thermal overload relay.
8 min read
ABB PSTX Soft Starter: Full Range Review
A full range review of ABB PSTX soft starters covering torque control, built-in bypass, current ratings, fieldbus options, and sizing versus PSE and PSR.
8 min read
MPCB Sizing for Star-Delta and Soft Starting
How to size an MPCB's thermal dial and magnetic trip for star-delta and soft-start motor circuits, including the 58% winding-current rule and soft-starter coordination.
10 min read
MCB Cascading and Back-up Protection
Cascading lets an upstream current-limiting device reduce let-through energy so a downstream MCB can be applied above its own rated breaking capacity, provided the pairing is a manufacturer-verified combination.
10 min read
RCD for EV Charger Circuits: Type B and 6mA DC (RDC-DD)
How EV charger circuits meet IEC 62955 with a Type B RCD or a Type A RCD paired with a 6 mA RDC-DD.
8 min read
3-Pole vs 4-Pole MCCB: Selection Guide
A clear decision rule for choosing 3-pole or 4-pole MCCBs based on TN-S, TN-C-S, TT, and IT earthing systems, neutral protection needs, and harmonic loading.
11 min read
Hysteresis, Trip Delay and Latching in Monitoring Relays
Hysteresis, trip delay and latching are the three settings that decide whether a monitoring relay trips on real faults or nuisance-trips on noise.
10 min read
ABB ACS580 vs Schneider ATV630 vs Siemens G120 VFD
A side-by-side comparison of the ABB ACS580, Schneider ATV630 and Siemens G120 VFDs on control method, overload duty rating, enclosure and fieldbus support.
9 min read
Ground-Fault and Stall Protection in Electronic Overload Relays
Electronic overload relays add vector-sum ground-fault sensing and a separate stall/locked-rotor timer on top of the standard thermal trip curve, functions a bimetallic relay cannot replicate.
9 min read
ABB PSTX vs Schneider ATS480 vs Siemens 3RW55 Soft Starter
A side-by-side comparison of the ABB PSTX, Schneider Altistart ATS480 and Siemens SIRIUS 3RW55 flagship soft starters on torque control, bypass, communication, current range and protection.
11 min read
How to Read an MPCB and Contactor Coordination Table
How to read the rows, Icc column, and Type 1/Type 2 declaration on an MPCB-contactor coordination table without breaking the tested combination.
9 min read
MCB Discrimination and Selectivity Explained
Why two MCBs in series often trip together on a large fault, what current discrimination actually guarantees, and when an upstream MCCB or fuse is the only fix.
10 min read
How to Size an RCBO for a Final Circuit
How to size an RCBO for a final circuit: matching In to design current and cable capacity, setting IΔn and type by load, and checking discrimination with the upstream device.
9 min read
MCCB Current Limiting and Let-Through Energy
How current-limiting MCCBs cut peak fault current and I²t let-through energy to protect downstream cable, busbar, and gear, and enable cascading protection, per IEC 60947-2.
11 min read
Insulation Monitoring Devices (IMD) for IT Earthing Systems
How insulation monitoring devices (IMDs) continuously measure insulation resistance in unearthed IT systems to catch the first earth fault before a second fault becomes dangerous.
9 min read
VFD Sizing for Constant vs Variable Torque Loads
How to match a VFD's Normal Duty or Heavy Duty overload rating to constant-torque and variable-torque loads, with the sizing steps, overload-margin formula, and derating factors that keep a drive...
10 min read
Overload Relay Coordination: Type 1 vs Type 2 with Contactor and SCPD
How IEC 60947-4-1 Type 1 and Type 2 coordination define what happens to a contactor and overload relay after a short circuit, and how to choose between them.
9 min read
Soft Starter Start Current, Starts Per Hour and Duty Cycle
How the current-limit setting, AC-53a duty codes and starts-per-hour thermal limits combine to size a soft starter correctly for cycling loads.
10 min read
How to Select and Set an MPCB for a Motor
A practical walkthrough of setting an MPCB's thermal dial to nameplate FLC, verifying the magnetic trip and trip class, and confirming Type 2 coordination with the contactor.
10 min read
Parts list
Sourcing a full parts list?
Paste your part numbers and quantities. We reply with price, stock and lead time per line.