SINOFUSE RS309-MF-S Series 700V/750V High-Speed Bolt-Connected Fuses
The SINOFUSE RS309-MF-S Series is a cylindrical bolt-connected high-speed fuse family designed for demanding AC and DC electrical protection applications. The series is rated at AC/DC 700V under IEC specifications and DC 750V under UL specifications.
RS309-MF-S fuses feature an aR utilization category, compact construction, low I²t characteristics, high breaking capacity, and resistance to current surges, mechanical vibration, impact, and demanding operating environments.
The series includes 16 rated-current options across two ranges: 70A–100A and 225A–800A. These models support electrical protection requirements in electric vehicle systems, energy storage, power conversion equipment, and industrial power electronics.
Key Specifications
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Manufacturer: SINOFUSE
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Series: RS309-MF-S
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Product Type: Cylindrical bolt-connected high-speed fuse
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IEC Rated Voltage: AC/DC 700V
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UL Rated Voltage: DC 750V
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Rated Current Ranges: 70A–100A and 225A–800A
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Utilization Category: aR
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AC Breaking Capacity: 100kA
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DC Breaking Capacity: 50kA
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DC Time Constant: ≤15ms
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Performance Standards: UL 248 and IEC 60269
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Application Reliability References: ISO 8820 and GB/T 31465
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Certifications: CE and UL, as specified by the manufacturer
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Environmental Compliance: RoHS
RS309-MF-S Model Range
The RS309-MF-S family includes 16 current ratings across three mechanical size groups: 3SA, 6TA, and 7TA. Each group has specific mounting requirements and recommended tightening torque.
| Size Code |
Rated Current |
Mounting Bolt |
Recommended Torque |
| 3SA |
70A, 80A, 90A, 100A |
M8 |
12 ±1 N·m |
| 6TA |
225A, 250A, 275A, 300A, 325A, 350A, 400A |
M10 |
21 ±1 N·m |
| 7TA |
450A, 500A, 600A, 700A, 800A |
M10 |
21 ±1 N·m |
Available RS309-MF-S Models
The manufacturer specifies the following current ratings across the RS309-MF-S family:
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3SA Models:
RS309-MF-S70A, RS309-MF-S80A, RS309-MF-S90A, RS309-MF-S100A
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6TA Models:
RS309-MF-S225A, RS309-MF-S250A, RS309-MF-S275A, RS309-MF-S300A, RS309-MF-S325A, RS309-MF-S350A, RS309-MF-S400A
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7TA Models:
RS309-MF-S450A, RS309-MF-S500A, RS309-MF-S600A, RS309-MF-S700A, RS309-MF-S800A
RS309-MF-S Technical Guide
For detailed electrical specifications, model-specific I²t characteristics, power-loss data, mechanical dimensions, mounting requirements, operating conditions, and application information, visit the dedicated RS309-MF-S Series technical page.
SINOFUSE RS309-MF-S Series 700V/750V High-Speed Bolt-Connected Fuse Technical Guide
Typical Applications
According to the manufacturer specification, the RS309-MF-S Series is intended for electrical protection applications involving electric vehicles, power conversion systems, energy storage equipment, and other demanding power-electronic installations.
- Electric vehicle traction and drive systems
- Power conversion equipment
- Energy storage and battery power systems
- Variable frequency controllers
- EV charging equipment
- Industrial power electronics
- Electrical conductors and vehicle equipment
- Short-circuit protection
- Backup protection
High-Speed Fuse Selection Considerations
The RS309-MF-S Series uses the aR utilization category, making fuse coordination and current-limiting performance important considerations in electrical protection system design.
When selecting an RS309-MF-S fuse, engineers should verify the exact model number, rated current, applicable voltage rating, breaking capacity, pre-arcing I²t, total clearing I²t, power loss, mechanical dimensions, and mounting requirements.
Because aR fuses are intended for partial-range protection, additional overload protection or appropriate system coordination may be required.
Operating Conditions
The manufacturer recommends that long-term continuous operating current should not exceed 80% of the fuse rated current under normal operating conditions.
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Normal Ambient Temperature: -5°C to 40°C
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Permitted Ambient Temperature: -40°C to 120°C
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Normal Operating Altitude: Up to 2000m
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Permitted Operating Altitude: Up to 4500m, subject to application requirements
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Pollution Degree: Class III
Applications involving elevated temperatures, enclosed installations, or high-altitude operating environments may require current derating or additional technical evaluation.
Related SINOFUSE Technical Resources
For additional information about SINOFUSE fuse families, technical specifications, and related circuit protection products, explore the following resources:
Series Selection Note: RS309-MF-S, RS309-MF, and RS309-MF-EV are separate fuse families. Similar voltage or current ratings do not establish electrical or mechanical interchangeability. Exact replacement suitability should be verified using the applicable manufacturer specifications.
Industrial Sourcing Support
Apexon Supply supports industrial buyers with SINOFUSE product identification, specification review, model selection, technical cross-reference, and international sourcing coordination.
For RS309-MF-S product availability, technical information, or quotation requests, please provide the exact model number, rated current, required quantity, and available application information.
