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Someone asked us:

Why photovoltaic fuse is used in a Photovoltaic system?

Here are 3 reasons help you to understand:

1. Short circuit or ground fault

If there is a short-circuit fault in the solar panel, PV combiner box or the wiring part of solar panel in photovoltaic array, there will be over-current. In addition, when the PV array wiring has a grounding fault, there also will be an over-current reaction. If there is no photovoltaic fuse at this time, it will damage the electrical components in the photovoltaic system, so in this case, the  PV fuse  is very key to provide effective over-current protection. Such as Bussmann solar fuse system.

2. Breakdown current of photovoltaic inverter

When the photovoltaic inverter breaks down in the photovoltaic system, it will result in big counter current, it will also damage the photovoltaic array cable and a photovoltaic panel also solar panel control box. Therefore, with using the photovoltaic inline fuse for inverter, when the counter current occurs and is within the rated breaking capacity of the solar fast acting fuse, the fuse will melt to provide protection to avoid the damage of photovoltaic array cable and solar panel caused by the return stroke current.

3. Battery Management System fault current

When the battery and battery pack in the photovoltaic array fail and cause the flow of peak value current, it can destroy the wire and solar panel control box. Once the panel fuses are installed between battery and inverter, it will blow in case peak current, so as to ensure that the whole photovoltaic array system and its wires will not be burnt out by the huge fault current.

Due to the complexity of the whole photovoltaic system, there are more cases of photovoltaic fuse fusing protection. No matter which kind of fault occurs, high-quality and reliable solar PV system protection fuse can blow quickly and provide the best protection for photovoltaic system equipment.

How to determine what size solar fuse to use?

Depending on the desired capacity of the solar photovoltaic system, there may be several solar panels in parallel to achieve higher currents and more power.

Solar systems that have three or more panels connected in parallel need to have each panel protected (systems that have less than three panels will not generate enough fault current to damage the conductors/equipment and therefore do not present a safety hazard as long as the conductor was sized properly based on local code requirements). 

Where three or more solar panels are connected in parallel a solar fuse on each panel will protect the conductors from damage and help minimize any safety hazards. It will also isolate the faulted panels so that the rest of the solar photovoltaic system can continue to generate electricity.  Protection of Conductors isolate damaged PV modules.

OK, Let's see how to select solar fuse Links for solar panel circuit protection.

Here is a photovoltaic fuse selection guide:

Once it has been determined that maximum short-circuit current ([N-1]*Isc) exceeds continuous current rating of conductor, follow the recommendations of selecting the proper photovoltaic fuse.

Example 1: Solar Panel String Fusing

Isc = 5.37A, Ipm = 4.83A 

Max System Voltage = 1000Vdc (max value of series panels) 

Conductor Size Formula = 1.56 * Isc = 1.56 * 5.37 = 8.38A 

Conduct Size = 14AWG or 2.5mm2 = 10.25A @ 80^oC

N = 4 (4 parallel Solar Panel Strings) 

Array Max Isc = (N-1) * Isc = (4-1) * 5.37 = 16.11A 

Array Max Isc is greater than conductor withstand, therefore panel fuses are required In = 1.56 x Isc (individual panel only) = 8.37A min 

fuse rating Select next higher std rating of 10A: PV-10A10F 

Fuse selected will protect selected conductor Min wire size: 14AWG or 2.5mm2 = 10.25A @ 80^oC

Typical Solar Panel Specification

Currently in Bussmann solar fuse system, there are following fuse ratings are available.

For example: PV 1000VDC 10x38mm Fuse

·       With range of 10x38mm fast blow fuse specifically designed for protecting photovoltaic strings.

·       These fuse links are capable of interrupting low overcurrent associated with faulted photovoltaic string arrays (reverse current, multi-array fault).

·       Catalogue Symbol/Fixing:

           PV-(amp rating) A10F - Cylindrical type need to mate with fuse holder

           PV-(amp rating) A10-T - Bolt type

           PV-(amp rating) A10-1P - Used on Printed Circuit Board

           PV-(amp rating) A10F-2P - Assembly on Printed Circuit Board

Advantage:

1, Easy for solar photovoltaic installers.

2, Cost competitive, price is around $2.5/pc;

3, High breaking capacity, protect different solar systems.

More Bussmann product, here is a summary.

Fuses	Fuse size	Volts	Amps	Hot sale fuse part #	Remark	Where it used	Picture
DCM	10x38mm	600VDC	1/10~30amp	DCM-10	Mate with CHPV, BPVM	• Combiner boxes • String protectors	Pls refer to Bussmann PV fuse catalog.
PVM	13/32" x 1-1/2"	600VDC	’4~30amp	PVM-30	Mate with BPVM	• Combiner boxes • String protectors
PVS-R	RK5	600VDC	20-400amp	PVS-R-100	NA	• Photovoltaic systems • Inverters • Photovoltaic system DC safety switches • Recombiner boxes
PV-_A10_	10x38mm	1000VDC	1-20amp	PV-15A10F	Mate with CHPV, BPVM	• Combiner boxes • Inverters • PV wire harnesses
HPV	In-line assembly	1000/1500VDC	1-20amp	HPV-DV-12A	HPV 1000 Vdc in-line PV fuse assembly	PV wire harness
PV-_A14F	14x51mm	1000/1100VDC	15-32amp	PV-32A14F	Mate with CHPV, BPVM	• Combiner boxes • Inverters
PV-_ANH_	NH1, 2, 3	1000VDC	32-400amp	PV-160NH1-B	Mate with  SD_-D-PV and TD_D-PV	• Recombiner boxes • Inverters
PV-_A10F85L	10x85mm	1500VDC	2.25-25amp	PV-20A10F85L	Mounts in Bussmann series CHPV15L85 DIN-Rail holder	Combiner boxes; wire harnesses
PV15M-4A-CT	Crimp terminal	1500VDC	4amp	PV15M-4A-CT	Recommend to use Sta-Kon® terminal crimping tool, catalog no. ERG4002	Wire harnesses; Other applications where an in-line PV fuse is desirable
PV-_A-_XL	XL 01, 1, 2, 3	1000/1500VDC	50-600amp	PV-200A-2XL-B	Recommended fuse blocks  • SB_ block	Recombiner boxes; Inverters
PV15M-XXX-H	Square body	1500VDC	63~400amp	PV15M-200-H	NA	Recombiner boxes; Inverters
Holder	Fuse size	Volts	Amps	Hot sale fuse part #	Remark	Where it used	Picture
CHPV_	10x38mm	1000VDC	30amp	CHPV1U	Mate with 10x38mm fuse.	• Combiner boxes • String protectors
Blocks	Fuse size	Volts	Amps	Hot sale fuse part #	Remark	Where it used	Picture
BPVM-_	10x38mm	1000	30amp	BPVM-1S	Mate with 10x38mm fuse. Cover: CVR-CCM(non-indicating)	• Combiner boxes • String protectors
CHPV15L85	10x85 and 14x85mm	1500	32amp	CHPV15L85	1, Mounting with 35mm DIN-Rail; 2, Mate with 10x85 and 14x85mm fast acting fuse.	• Combiner boxes • String protectors
SB_XL-_	01XL to 3L	1500	Up to 630amp	SB2XL-S	1, 1-pole PV fuse block; 2, Mate with accessory: FEH1500(Fuse extraction handle available for sizes 01XL to 3L)	Tool for assembly
SD_-D-PV and TD_D-PV	NH1, 2, 3	1500	Up to 630amp	SD2-D-PV	NH PV fuse block; Mate with fuse handle: FEH; Shroud kits:SD12-SK; Phase barrier kits:SD12-PB; Microswitches: BVL50; Neutral links: SDL-2	• Recombiner boxes • Inverters