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Siemens 5SY4340-8FA — 3-Pole MCB (DIN Rail)

Siemens 5SY4340-8FA SENTRON MCB, 40 A, 3P, D-Curve, 10 kA

MPN5SY4340-8FA

Siemens SENTRON 5SY4 series, miniature circuit breaker, 3-pole, 40 A, D tripping characteristic, 10 kA breaking capacity at 400 V AC per EN 60898, 440 V AC multi-phase rated voltage, IP20 with connected conductors, 3 MW units wide.

Siemens 5SY4340-8FA datasheet (PDF)
Sourced new & surplus through independent channelsAuthenticity-screened · ESD-safe packingListing updated Aug 2026

Specifications

5SY4340-8FA — Identification
ParameterValue
Brand nameSENTRON
Number of poles3
Pole configuration3P
Suitability for operationMechanical engineering / industry
5SY4340-8FA — Protection
ParameterValue
Tripping characteristic (curve)D
Overvoltage categoryIII
IP protection classIP20, with connected conductors
Pollution degree3
5SY4340-8FA — Electrical
ParameterValue
Rated current (AC)40 A
Rated voltage (AC, multi-phase)440 V
Neutral conductor switchingNo
5SY4340-8FA — Mechanical
ParameterValue
Modular width units3
Mounting positionany
Width54 mm
Height90 mm
Depth76 mm
Installation depth70 mm
Terminal tightening torque, max.75 °C
Terminal tightening torque, min.-40 °C
Combined terminal, topYes
Combined terminal, bottomYes
Fastening methodQuick assembly system
SealableYes
5SY4340-8FA — Environmental
ParameterValue
Halogen-freeYes
Silicone-freeYes
Influence of surrounding temperaturemax. 95% to 55°C, max. 55% to 70°C, max. 35% to 75°C

Product details

The Siemens 5SY4340-8FA is a SENTRON miniature circuit breaker (MCB) with a D tripping characteristic, rated 40 A at 35 °C, 3-pole construction, and a 10 kA breaking capacity per EN 60898 at 400 V AC. Multi-phase operating voltage is 440 V AC. The IP20 rating applies once conductors are connected — standard for enclosed panel installation.

The 40 A rating holds at 35 °C ambient. At 40 °C it derates to 38.08 A; at 45 °C to 37.08 A; at 50 °C to 36.08 A; at 55 °C to 35 A. Maximum ambient is 75 °C, minimum -40 °C.

Depth is 76 mm, height 90 mm, width 54 mm (3 MW). Installation depth 70 mm. Sealable design allows lockout/tagout on the toggle.

Frequently asked questions

Where can I buy 5SY4340-8FA and how do I get a price?

This part is sourced and quoted to order against an RFQ through independent distribution. Submit an RFQ for current availability and pricing — no stock count or price is published here.

What is the D-curve on this MCB used for?

The D tripping characteristic (10 to 20 times In) is designed for circuits with high inrush currents — motor starters, transformers, welding equipment — where a B or C curve would nuisance-trip on startup.

What is the breaking capacity of the 5SY4340-8FA?

10 kA per EN 60898 at 400 V AC. That is the rated short-circuit capacity for the MCB — it can safely interrupt faults up to 10 kA without welding or rupturing.

Will 5SY4340-8FA drop into a panel that was specified around 5SY7210-7CC without rewiring?

Both are 3-pole SENTRON MCBs on the same DIN-rail footprint (3 MW wide), so mechanical fit is identical. The 5SY4340-8FA is a 40 A D-curve; the 5SY7210-7CC is a different rating and curve — verify the branch circuit's load and coordination before swapping.

MPN
5SY4340-8FA