Why this FAQ?
Engineers need clear, spec-driven guidance to select and apply the 25LET correctly for semiconductor protection. This FAQ consolidates ratings, standards, fitment, and buying info for faster decisions.
What is the Eaton Bussmann 25LET fuse and its key ratings?
The 25LET is a Bussmann series high-speed British Standard fuse (LET type), Class aR for semiconductor protection. Ratings: 25 A, 280 VAC, 150 VDC (UL), breaking capacity 200 kA RMS Sym. on AC and 50 kA at 150 VDC. Designed for fast fault clearing in drives, rectifiers, and DC bus protection.
Which standards and approvals does 25LET meet?
It is IEC rated and UL Recognized, with CE Marking and RoHS compliance. Designed and tested to BS88 Part 4 and IEC 60269-4. For UL file numbers or regional approvals, refer datasheet / contact Shansen for confirmation.
Where is the 25LET typically used?
Applications include semiconductor protection (thyristors/IGBTs), DC common bus, DC drives, and power converters/rectifiers. As a Class aR (partial-range) fuse, it is intended for short-circuit protection in these circuits; provide separate overload protection if required.
What are the physical dimensions and mounting details?
Body size is 55 × 18 × 18 mm, approx. 32 g. Connection is blade end × blade end with offset bolted tags; stud mounting on M6 hardware with 41 mm center-to-center spacing. Mount on a suitable BS88 base/busbar; tighten per manufacturer torque—refer datasheet for exact values.
Pre-arc I²t is 18 A²s and total clearing I²t is 250 A²s (reference values; test conditions per datasheet). Typical watt loss is 4 W. Use these to verify semiconductor let-through energy and thermal performance. The base fuse has no built-in indicator (Fuse indicator: None; IMGL: No). Accessory options noted for this series include MAI (fuse indicator) and MBI (microswitch/adaptor); verify accessory fitment for 25LET before ordering.What are the I²t and power loss values?
Does the 25LET include an indicator or microswitch?
How should I apply the interrupt ratings safely?
On AC systems up to 280 V, the interrupt rating is 200 kA RMS Sym.; on DC up to 150 V, it is 50 kA. Confirm your available fault current and system voltage fall within these limits, and ensure proper coordination with upstream devices. For time-current curves and coordination data, refer datasheet / contact Shansen.
What installation and safety considerations apply?
Use appropriate BS88 holders/busbars (e.g., suitable bases like TI500 where applicable) and ensure correct polarity/clearances in DC applications. De-energize before service, use M6 hardware and flat/spring washers as specified, and verify conductor tightening torque per datasheet. Maintain ventilation to manage the 4 W loss.
How do I order the 25LET in India?
Specify Catalog Number 25LET (UPC 051712833233; EAN 5027590470896) and required quantity. Shansen Enterprises is an authorized Eaton Bussmann channel partner, serving Tamil Nadu with pan-India delivery. Share your specs via WhatsApp for quick quotes and stock/lead-time confirmation.
