SPF 1000VDC Solar Fuses Littelfuse SPF (Solar Protection Fuse) 1000VDC Solar Fuses have been specifically designed for the ever-increasing voltage requirements of photovoltaic (PV) systems. The SPF series is UL recognized to safely interrupt circuits up to 1000VDC maximum. These midget fuses (10mm x 38mm) safety protect PV modules and their conductors from reverse overcurrent conditions. Littelfuse SPF 1000VDC Solar Fuses are available in 1A to 30A ratings to match specific requirements in a variety of applications, including inverters, combiner boxes, and battery charge controllers.