3P WH5-125 Isolator Switch Three Pole Power Disconnect

A 3P isolator switches all three phases (L1, L2, L3) of a three-phase circuit simultaneously through one mechanical handle. There is no neutral pole in a basic 3P device; if you need neutral switching too, you would select a 4P version. Three-pole isolation is required for any three-phase motor, heater, or supply that must be fully de-energized for maintenance.

The 3P isolator is a manual on/off switch with visible contact separation and no automatic trip. The 3P MCB is an automatic protective device that opens all three phases on overload or short circuit. The isolator is selected for isolation and load switching; the MCB is selected for fault protection. They are commonly installed in series: isolator upstream as the main disconnect, MCBs downstream as branch protection.

Yes, provided the motor's full-load current is within the isolator's rated operational current (Ie = 125 A) and its utilization category supports motor switching. The WH5-125 is typically rated AC-22A (mixed resistive and inductive loads). For direct-on-line motor switching at the motor's locked-rotor current, confirm AC-23A rating on the datasheet; otherwise upstream contactors should do the frequent motor switching and the isolator should only isolate.

125 A per pole is the maximum continuous current each phase can carry. On a 400 V three-phase system this equates to approximately 75 kW of balanced three-phase load (√3 × 400 V × 125 A ≈ 86.6 kVA). The neutral, if present, is not switched by a 3P device and must be terminated on the panel neutral bar.

Connect incoming L1, L2, L3 to the top terminals 1, 3, 5 (line side), and outgoing L1, L2, L3 to the bottom terminals 2, 4, 6 (load side), preserving the same phase order. Terminals are numbered 1-2 (pole 1), 3-4 (pole 2), 5-6 (pole 3). Use correctly sized copper cables (around 25–35 mm² for 125 A), tighten to rated torque, and re-check phase sequence on the load side after connection.

No. It will not open automatically on a fault. The upstream protection (MCB, MCCB, or fuses) must clear any short circuit. The isolator must withstand the short-time current let through by that upstream device for the duration of the fault clearance — verify this coordination in the product's short-time withstand (Icw) rating.

Move the handle fully to OFF. A padlock hole on the handle accepts one or more padlocks (often up to three) so that multiple workers can each lock the device with their own personal lock. With the handle locked, no one else can re-energize the circuit. After locking, use a calibrated voltage tester to confirm zero volts on all three load terminals before starting work.

IEC 60947-3 is the IEC product standard for low-voltage switchgear — switches, disconnectors, switch-disconnectors, and fuse-combination units. It defines rated voltages up to 1000 V AC, rated currents, utilization categories (AC-21 for resistive, AC-22 for mixed, AC-23 for motor loads), isolation requirements, and type-test protocols. A WH5-125 marked to IEC 60947-3 has been tested to these internationally recognized criteria.

Yes — a 3P 125 A isolator is a common choice as the main disconnect of a three-phase distribution board, workshop panel, or machine control cabinet. It provides a visible off point for the whole installation, but it must still be backed by upstream overcurrent protection (e.g., an MCCB or fuses) on the supply side.

It clips onto a standard TH35-7.5 mm DIN rail. Hook the top of the unit over the rail, press the bottom firmly until the retaining latch clicks, and verify the unit is seated and cannot be pulled off. Keep the device within ±5° of vertical, allow clearance above and below for wiring, and do not install in a sealed enclosure without adequate ventilation at full 125 A load.