The Ferrule Form Factor

Both FWH and FWP fuses use a cylindrical body with ferrule (cap) terminals -- the same form factor as standard IEC 60269-4 semiconductor fuses. This cylindrical ferrule design offers practical advantages: compatibility with standard DIN rail clips and busbar-mounted fuse holders; uniform heat dissipation without hot spots; proven automotive vibration and thermal cycling performance meeting ISO 16750 requirements; and field replaceability by trained technicians without specialized tools.

FWH Series -- 500 Vdc, 50 kA

FWP Series -- 700 Vdc, 50 kA

FWJ Series -- 800 Vdc, 50 kA (Imperial Ferrule)

Voltage Selection: FWH vs FWP vs FWJ

Select the lowest voltage family that provides adequate margin above your maximum system voltage. For a 400V nominal system (approximately 460V peak at full charge), FWH at 500 Vdc provides 8.7% voltage margin -- acceptable for most applications. For a 600V nominal system (approximately 690V peak), FWP at 700 Vdc provides only 1.4% margin -- marginal for some applications. FWJ at 800 Vdc provides 15.9% margin for the same 600V system, often preferred for robust protection. The FWJ uses imperial (inch-based) ferrule dimensions, which may affect holder compatibility compared to the metric FWH-C and FWP-C series. Verify holder compatibility before specifying.

FWH/FWP/FWJ Applications in EV and ESS

 In EV: FWH-C is used for OBC AC input protection (500V rating provides adequate margin above 400Vac input), DC-DC converter input/output protection, and low-voltage battery pack protection in 200-400V architectures. In ESS: FWH-C for battery rack combiner protection (500V tier) and PCS DC side protection for 500V-class BESS. FWP for 600-700V battery bus protection where FWH's 500V rating is insufficient. FWJ for 800V battery bus protection in a ferrule form factor where the 170M square-body size is too large.