WKC 3 Pole 10kA MCB – 40A D Curve (WKC340D)
18th Ed. Compliant
2-Year Warranty
UK Stock
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The WKC340D 3 Pole 10kA MCB is a 40A D Curve breaker designed to protect three-phase circuits with very high inrush currents. With a 10kA breaking capacity and compliance with BS 7671 (18th Edition), it delivers reliable overload and short-circuit protection for demanding industrial applications such as welders, large motors,...
The WKC340D 3 Pole 10kA MCB is a 40A D Curve breaker designed to protect three-phase circuits with very high inrush currents. With a 10kA breaking capacity and compliance with BS 7671 (18th Edition), it delivers reliable overload and short-circuit protection for demanding industrial applications such as welders, large motors, compressors, and transformers. Compact, DIN rail mountable, and bi-directional, it provides robust protection where standard MCBs would nuisance trip.
Installer Tip: Choose D Curve MCBs only where circuits experience extreme inrush. For resistive loads, see the B Curve. For moderate inductive loads, select the C Curve.
Key Features
- 40A rated current – for large three-phase industrial circuits
- D Curve tripping – trips at 10–20x In
- 10kA breaking capacity – withstands high prospective fault currents
- 3 Pole design: protects all three phases
- Bi-directional: can be wired from top or bottom
- Applications: welders, transformers, compressors, heavy motors, plant machinery
Compare 40A 3 Pole Variants
| Model | Curve | Rated Current | Breaking Capacity |
|---|---|---|---|
| WKC340B | B Curve | 40A | 10kA |
| WKC340C | C Curve | 40A | 10kA |
| WKC340D (This Product) | D Curve | 40A | 10kA |
Where is the WKC340D typically used?
In large three-phase circuits with heavy inrush such as welders, compressors, motors, and transformers.
How does D Curve differ from B and C?
B Curve trips at 3–5x In, C Curve at 5–10x In, while D Curve trips at 10–20x In — suitable for very high inrush applications.
What does 10kA breaking capacity mean?
It’s the maximum fault current the breaker can safely interrupt without failure. 10kA is standard for industrial and commercial boards.
Is the WKC340D bi-directional?
Yes — the breaker can be wired from either the top or bottom terminals.
Can this be used in EV or PV installs?
No — for EV and PV, C Curve models are typically specified. D Curve is reserved for heavy inrush industrial equipment.
- Product Code: WKC340D
- Type: Miniature Circuit Breaker (MCB)
- Poles: 3P (three-phase)
- Rated Current: 40A
- Curve: D Curve
- Breaking Capacity: 10kA
- Mounting: DIN rail, 18mm per module
- Functions: Overload & short-circuit protection, switching, isolation
- Compliance: BS 7671 (18th Edition)
- Endurance: 4000 mechanical / 2000 electrical operations
- Brand: WCED
Install in industrial or commercial boards where circuits experience very high inrush demand. Curve selection is key:
- B Curve: resistive circuits (lighting, sockets)
- C Curve: inductive loads with moderate inrush (motors, HVAC, EV chargers)
- D Curve: welders, compressors, transformers, heavy motors (high inrush)
Ensure fault levels do not exceed 10kA. All installations must comply with BS 7671 and be completed by a qualified electrician.
