FXD63B250 SIEMENS

FXD63B250 Siemens Basis unit

Brand：SIEMENS Model number：FXD63B250

Country of origin: Germany Product weight：0.55kg

HS code：8517623990

Product Details：

Product Dimensions：

The FXD63B250 belongs to the FXD6 series, which represents a robust class of molded case circuit breakers engineered for high-capacity branch and feeder circuit protection. This particular unit features a non-interchangeable thermal-magnetic trip unit, meaning it utilizes a bi-metal strip for time-delayed overload protection and an electromagnetic element for instantaneous short-circuit protection. It is a 3-pole device rated for medium-to-heavy industrial loads and is designed to fit seamlessly into standard Siemens panelboards, switchboards, or standalone enclosures. The frame structure is constructed from a high-dielectric, glass-reinforced polyester material that safely contains electrical arcs and withstands immense mechanical stress during a fault condition.

Product Parameters

Product Brand: Siemens Sentron
Frame Type: FXD-Frame (FXD6)
Poles: 3-Pole configuration
Amperage Rating: $250 \text{ A}$ continuous current rating at $40\text{°C}$
Voltage Ratings: Supports up to $600 \text{ VAC}$ or $250 \text{ VDC}$ maximum
Interrupting Capacity: Rated at $65 \text{ kA}$ at $240 \text{ VAC}$ , $35 \text{ kA}$ at $480 \text{ VAC}$ , and $22 \text{ kA}$ at $600 \text{ VAC}$ (standard interrupting class)
Trip Unit Type: Non-interchangeable thermal-magnetic trip unit
Terminal Connections: Typically supplied with standard mechanical line and load side lugs accommodating standard copper or aluminum industrial wiring gauges
Mounting Configuration: Bolt-on style, suitable for horizontal or vertical installation orientations within compatible enclosures
Standards Compliance: UL 489 listed, CSA certified, and compliant with NEMA AB1 standards

Product Advantages

A major advantage of the FXD63B250 is its Proven Thermal-Magnetic Reliability. The mechanical trip mechanisms function independently of external control power or microprocessor logic, ensuring the breaker will always trip during an overcurrent event even if the system experiences a complete control voltage failure. The High Interrupting Rating allows it to safely clear high-magnitude fault currents without exploding, preserving the integrity of downstream equipment and upstream switchgear.

Additionally, the Compact Frame Design packs a heavy-duty $250 \text{ A}$ rating into a space-efficient enclosure size, allowing panel designers to optimize space inside distribution boards. The unit's Durable Construction also minimizes mechanical wear on the internal contact pads, guaranteeing a long service life and reduced lifecycle maintenance costs.

Important Considerations and Precautions

When installing or servicing the Siemens FXD63B250, Strict Electrical Safety Compliance must be maintained; always lock out and tag out all upstream power feeds before mounting or adjusting wire connections to eliminate arc flash risks. Terminal Torque Specifications must be strictly adhered to using a calibrated torque wrench; loose lugs will cause excessive localized heating that can lead to nuisance tripping or terminal meltdown, while overtightening can crush and weaken the conductors.

Because this breaker uses a Thermal-Magnetic Trip Unit, its ambient temperature matrix matters; if the breaker is mounted in an enclosure that exceeds $40\text{°C}$ , it will trip below its $250 \text{ A}$ nominal rating, and appropriate derating calculations must be performed. Furthermore, ensure that the Interrupting Rating matches or exceeds the calculated Available Short-Circuit Current (ASCC) at the point of installation; applying a breaker to a grid with a higher fault capacity than the breaker's rating is a severe hazard. Lastly, periodically test the mechanical trip free mechanism using the Push-to-Trip Button on the front cover during routine system maintenance.

Product Applications

The Siemens FXD63B250 is exceptionally well-suited for medium-voltage industrial and commercial main or branch circuit protection.

Industrial Manufacturing Facilities: Serving as the main feeder breaker for high-power machine centers, heavy conveyor motors, and assembly line panels.
Commercial Building Distribution: Installed within panelboards or switchboards to distribute power across specific floors, large HVAC chillers, and localized lighting transformers.
Motor Control Centers (MCC): Acting as the upstream thermal-magnetic protection device for high-horsepower motor starters and variable frequency drive cabinets.
Renewable Energy Infrastructure: Utilized in solar combiner panels or wind turbine power distribution subsystems to isolate major power conversion blocks.
Data Centers and Infrastructure: Providing robust branch circuit isolation for critical infrastructure support systems like backup generators and large UPS battery rooms.

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