New Industry Products

Littelfuse Expands its Line of 1500V Solar String Fuses

January 07, 2021 by Gary Elinoff

The new fuses include models rated from 35 to 60 amps with fault currents of up to 50 kA

The new members of the SPXV series of solar string fuses integrate with Littelfuse’s LFXV15 fuse block and cover holder. Together, this pair is aimed at protecting photovoltaic (PV) from short circuits and overloads that might otherwise damage solar panels and solar installations.


Littelfuse Expands its Line of 1500V Solar String Fuses Figure
Image courtesy of Littelfuse 


"Littelfuse understands the need to provide higher amperage protection, while containing costs, to keep solar competitive with other forms of power generation," said Sakthidharan Krishnamoorthy, product manager, Littelfuse Industrial Business Unit. "With available ampere ratings up to 60 A, more solar fuse strings can be pre-combined to reduce the number of inputs into combiner boxes, thereby decreasing installation time and labor costs." 

Measuring 20 by 127 mm, the 35 to 60 amp solar SPXV series solar fuses offer higher amperage protection in less space.  The series companion product, the LFXV15 series fuse block and cover holder, feature a dead-front cover to enhance personnel protection. 


Image courtesy of LFXV15 Series Fuse block and Cover Data Sheet
Image courtesy of LFXV15 Series Fuse block and Cover Data Sheet


Their narrow width enables the accommodation of a greater number of blocks per panel to save space. The well-ventilated design allows the Littelfuse SPXV solar fuses that they deploy to keep cooler, despite the high current they transmit and the possibility of high ambient temperatures.

The fuse block holders feature a 35 mm DIN-rail mounting option, facilitating quick assembly and installation. The SPXV solar fuses that they mount require no tools for removal or for replacement. 


Members of the SPXV series

Littelfuse provides a complete listing of the SPXV series. All are rated at a maximum of 1500 volts, with currents ranging from 1 to 60 amps. The reader will notice each device is specced at an Interrupting Rating of 50,000 Amp. This is an important consideration that Littelfuse describes at length in its Fuse Characteristics, Terms and Consideration Factors.

Interruption Rating, aka breaking capacity or short circuit rating, refers to the maximum amount of current that the fuse can handle, an amount far greater than the point at which it simply blows and safely shuts off current flow. During a short or a serious fault, a fuse may be subjected to many times rated current. Interruption Rating is how much current the fuse can handle, even momentarily, while still guaranteeing that the fuse remains intact and doesn’t explode.


Electrical Characteristics

As described in the data sheet, members of the series exhibit cold resistance the varies inversely in proportion to rated current, ranging from 0.9256 to 0.0033Ω. 

Watts loss at 100% capacity is 1.67 watts for the 1 amp fuse, and 20.93 watts for the 60 amp fuse. However, the loss as a percentage of total power carried is lower for the larger fuses.

At temperatures below about 80°F, current capacity of the fuse rises slightly, and above that point, it declines.



  • Inverters
  • Combiner boxes


Environmental Considerations for the SPXV series of solar fuses 

Approvals: UL 248-19 Listed (File: E339112 )

Applicable Standards

  • UL 248-1, 248-19
  • IEC 60269-6 (SPXV 25 and 30 amp fuses meet electrical performance only)



  • RoHS Compliant