Switching and Protection Products Guides

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Page 2: 55 technical guides for choosing Switching and Protection Products products: selection criteria, standards, common mistakes and frequently asked questions.

What Is a Motor Phase Protection Relay? Types and Selection Criteria — A motor phase protection relay protects three-phase motors by monitoring phase loss, phase sequence, asymmetry, over/undervoltage and, via PTC, winding temperature.
What Is a Medium Voltage Circuit Breaker? Types and Selection Criteria — A medium voltage circuit breaker is a switching device that switches load current above 1 kV and interrupts short-circuit current on a protection relay's command.
What Is a Horizontal Load Break Switch? Types and Selection Criteria — A horizontal load break switch is a fuse switch disconnector that holds NH fuses in carriers side by side, mounts on a plate or busbar and can be opened and closed under load.
What Is a Voltage Protection Relay? Types and Selection Criteria — A voltage protection relay is a monitoring relay that disconnects the load through its output contact when the supply voltage leaves the set lower or upper limit.
Pole-Changing and Reversing Cam Switches Selection Guide — When selecting pole-changing and reversing cam switches, compare 1-0-2 reversing/changeover operation, Dahlander two-speed motor wiring, pole count and AC-3 current.
Standard Step Switches Selection Guide — It is used to change the operating step by hand on tapped transformers, heater resistor groups, multi-speed fans and similar loads.
On-Off Cam Switches (0-1) Selection Guide — When selecting 0-1 On-Off rotary cam switches, compare 10 A–315 A rated current, 1 to 4 poles, panel/base/enclosed mounting and padlockable Yellow-Red main switch handles.
Transfer Switches (ATS / Changeover) Selection Guide — When selecting transfer switches (manual changeover or automatic ATS), compare 1-0-2 switching positions, pole count (3P/4P), AC-31B/AC-33B rating and motor control.
Open Type Power Circuit Breakers (ACB) Selection Guide — An open type power circuit breaker (ACB) is a low-voltage circuit breaker that extinguishes the arc in air and operates at high rated currents.
Molded Case Circuit Breakers (MCCB) Selection Guide — It is used at the incomers and outgoings of main and sub-distribution panels, at generator outputs and on machine supplies to protect and switch the line.
Contactor Accessories Selection Guide — How to select mechanical interlocks, coil surge suppressors (RC/varistor/diode), star-delta power links, and replacement coils for contactors.
Motor Control and Protection Equipment Selection Guide — How to size and coordinate motor protection switches, thermal overload relays, direct-on-line starters, and soft starters under IEC 60947-4-1.
Switch and Breaker Accessories Selection Guide — Selection criteria for shunt trips, undervoltage releases, auxiliary contacts, motor operators, and rotary handles for MCCBs and ACBs.
Switchgear Auxiliary and Trip Alarm Contacts Selection Guide — How to choose front-mount and side-mount NO/NC auxiliary contact blocks and fault trip alarm contacts for MCBs, MPCBs, and contactors.
What is the difference between a motor protection circuit breaker and a thermal overload relay? — Compare MPCBs and thermal overload relays in motor starter design: short-circuit protection, main power contacts and contactor coordination.
What is the difference between an RCCB and an RCBO? — Understand the difference between an RCCB (earth leakage only) and an RCBO (combined MCB + RCD in a single unit) for electrical panel design.
What is the difference between an MCB and an MCCB? — Compare MCB and MCCB circuit breakers across rated current, short-circuit breaking capacity, adjustable trip units and panel mounting.
What Is Star-Delta Connection? Switch Selection Guide — Star-delta reduces the starting current to one third by connecting the motor first in star and then in delta; check current, size and enclosure when selecting a switch.
What Is a Surge Arrester? Types and Selection Guide — A surge arrester protects the installation by diverting lightning and switching overvoltages in the low voltage network to ground; a guide to types and selection.
What Is a Phase Protection Relay? Selection Guide — A phase protection relay monitors a three-phase network for phase loss, phase sequence and voltage imbalance; here are the selection criteria.
Contactors Selection Guide — A contactor is an electromechanical switch that opens and closes its main contacts with the control voltage applied to its coil. Types, AC-1/AC-3 categories and selection steps.
What Is a Residual Current Device? Types and Selection — A residual current device measures the difference between phase and neutral currents and trips the circuit above a threshold. AC, A and B types, 30/300 mA, pole choice.
Fuses Selection Guide — A fuse is a device that protects the cable and equipment by interrupting the circuit on overcurrent and short circuit. Types of miniature circuit breakers, blade fuses and cartridge fuses, and how to choose.
Switches Selection Guide — Switches come in molded case, open type power, motor protection, cam, load break and transfer types; select by rated current and application.