Military Relay B3T1-250.0 250A Specifications - Military Metal Relay B3T1-250.0 80-3601 B-D2-C1-G-H 250A 80V

Military Relay B3T1-250.0 250A Specifications: The Definitive Technical Reference

In the realm of ultra-high-current switching, where system integrity and safety are paramount, specifications are not merely numbers—they are the definitive blueprint for performance under extreme stress. The B3T1-250.0 Military Metal Relay (complete designation: 80-3601 B-D2-C1-G-H 250A 80V) stands as a benchmark for 250-ampere DC power control in mission-critical applications. This comprehensive technical reference decodes its complete specification sheet, providing procurement engineers and system architects with the granular data needed to confidently integrate this powerhouse into Aircraft Engine start systems, heavy-duty Industrial Power distribution, and next-generation Military Aviation platforms.

Anatomy of a Specification: Decoding the Full Designation

Understanding the complete part number is the first step to mastering its specifications. The designation 80-3601 B-D2-C1-G-H is a structured code revealing its pedigree and core attributes.

1. 80-3601: The governing drawing or specification number, often referencing a detailed military or aerospace standard that defines materials, processes, and test requirements.
2. B: Series identifier, typically indicating a specific frame size and mechanical configuration optimized for high-power duty.
3. D2: Contact configuration and rating code. "D" usually denotes main power contacts, with "2" specifying the size, material, and force.
4. C1: Coil specification code, defining the voltage, resistance, and insulation class of the electromagnetic actuator.
5. G: Environmental and sealing class. Often indicates a hermetically sealed or ruggedized enclosure suitable for harsh environments.
6. H: Terminal/connection style or a specific performance/revision level (e.g., H for high-vibration version).
7. 250A 80V: The headline electrical ratings: 250 Amperes continuous current at 80 Volts DC.

Comprehensive Electrical Specifications Analysis

The following parameters define the operational and safety envelope of the B3T1-250.0, distinguishing it from commercial-grade Industrial Power Relays.

1. Contact & Load Switching Parameters (The Core Spec)

2. Coil & Control Circuit Specifications

Mechanical, Environmental & Lifecycle Specifications

These specs ensure physical survivability and define operational lifespan, key for OEM/ODM Manufacturers calculating total cost of ownership.

• Mechanical Durability (No Load): > 25,000 operations. Validates the robustness of the hinge, armature, and spring assembly.
• Electrical Durability (At Rated Load): > 5,000 operations at 250A, 80VDC, L/R ≤ 10ms. Defines the functional switching life under design conditions.
• Operating Temperature Range: -65°C to +125°C. Full functional performance across this range, including coil operation and contact integrity.
• Storage Temperature Range: -65°C to +150°C.
• Vibration Resistance: 10-2000 Hz, 15g (MIL-STD-202, Method 214). Essential for engine-mounted or vehicle applications.
• Shock Resistance: 50g, 11ms (MIL-STD-202, Method 213). Withstands battlefield or severe transportation shocks.
• Ingress Protection: Typically IP67 or hermetically sealed (per MIL-STD-810).
• Terminals: Plated copper alloy studs (e.g., M10). Specified torque: 25-30 Nm.

Industry Trend: Specification Transparency and Digital Twins

The demand is shifting from simple datasheet limits to comprehensive, traceable performance data. Leading-edge manufacturers provide statistical performance distributions (e.g., contact resistance S-curves, operate time histograms) and are developing digital twins of components like the B3T1-250.0. These virtual models, fed with real test data, allow system engineers to simulate performance under unique load profiles or environmental sequences before physical integration, reducing program risk for complex Military Aviation or Train propulsion projects.

5 Critical Specification Scrutiny Points for Russian & CIS Heavy Industry

1. Low-Temperature Performance Certification: Demand certified test reports showing successful make/break operations at -65°C with measured coil operate voltage, time, and contact resistance. This is non-negotiable for Arctic equipment and winter operations of Plane ground power units.
2. GOST/IEC Cross-Reference for Key Parameters: A formal document mapping each major specification (I_th, I_cm, dielectric strength) to the equivalent test clauses in relevant GOST standards (e.g., GOST R 50030) and IEC 60947-4-1.
3. Material Analysis Certificates (MACs): Full traceability for the contact material (AgW/AgSnO₂ lot), copper alloy for terminals, and coil wire insulation class, proving compliance with stringent material GOSTs.
4. Short-Circuit Coordination Data (I²t, Peak Let-Through): Detailed curves showing the relay's specific let-through energy and peak current under short-circuit conditions, essential for designing selective coordination with upstream fuses or breakers in naval or industrial power systems.
5. Validation of "G" and "H" Suffix Requirements: Explicit documentation proving how the sealing ("G") and terminal/revision ("H") features meet or exceed the requirements of the base drawing 80-3601.

YM's Specification Assurance: Precision Engineering at Scale

Guaranteeing that every B3T1-250.0 meets its rigorous specifications requires a fusion of heavy industry capability and aerospace precision. Within our 500,000 sq.m. mega-facility, the production of this relay is a showcase of advanced manufacturing. We employ electron-beam welding for critical joints to ensure strength and consistent thermal properties. Each relay's contact alignment and pressure are set by robotic systems with force feedback, ensuring the critical ≤ 0.08 mΩ resistance spec is consistently achieved. This process-centric approach is the foundation of our High Quality Aviation and defense manufacturing philosophy.

R&D's Contribution to Specification Excellence: Magnetic Blow-Out Optimization

The Breaking Capacity (I_cn) specification is directly enabled by our R&D team's work in computational magnetics. Using 3D finite element analysis (FEA), they have optimized the geometry and strength of the permanent magnet blow-out system. This simulation-led design ensures the magnetic field strength is precisely calibrated to stretch and cool the 250A DC arc rapidly across the arc chutes, enabling it to meet and exceed the 375A breaking specification reliably, a technology that also informs our designs for Solid State Relay for Drone protection circuits.

Application & Implementation Guidelines Based on Specifications

Correct implementation is critical to realizing the specified performance in the field.

1. Thermal Derating & Heat Sinking:
   • The 250A rating is at 40°C ambient. For higher ambient temperatures (e.g., inside a Train power cabinet), consult derating curves.
   • Mount on a flat, clean surface using thermally conductive paste if specified to aid heat dissipation through the baseplate.
2. Connection Integrity (The Single Most Critical Factor):
   • Use busbars or cables rated for >250A. Ensure perfect surface contact.
   • Adhere strictly to terminal torque specification (e.g., 28 Nm ±10%). Under-torquing creates hot spots; over-torquing can damage threads.
   • Use a calibrated torque wrench and follow a star-pattern tightening sequence.
3. Driver Circuit Design:
   • Size driver components (contactors, MOSFETs) for the coil's ~6.2A inrush current.
   • Incorporate a robust freewheeling diode (rated for coil energy) and consider an RC snubber across the coil to protect control electronics from back-EMF.
4. Safety Interlocks: For systems with large stored energy (batteries, capacitors), implement a maintenance disconnect or pre-charge circuit to avoid making onto a fully charged capacitor bank, which could exceed the Making Capacity spec.

Governing Standards & Qualification Framework

The B3T1-250.0's specifications are validated against a hierarchy of demanding standards, providing multiple layers of assurance:

• Primary Performance Standard: Likely governed by a detailed military specification like MIL-PRF-24236 for high-current DC contactors or a specific platform standard (e.g., for a tank or aircraft).
• Base Component Standards: Inherits test methods and requirements from MIL-PRF-6106 (relays) and MIL-STD-202 (environmental).
• Commercial Equivalency: Performance aligns with the intent of IEC 60947-4-1 for industrial contactors, though with more severe environmental thresholds.
• Quality Management: Manufactured under AS9100 / ISO 9001 quality systems.