مصهر وحامل الطاقة الشمسية: 7 نقاط اختيار أساسية يجب على مهندسي تركيب أنظمة الطاقة الشمسية الكهروضوئية إتقانها

An underrated solar fuse or a poorly sealed solar fuse holder may continue to reduce the operating performance of the entire photovoltaic system for many years without detection. In more serious cases, it may even trigger an arc fault, which can lead to roof fires. Therefore, you need to fully understand the solar fuse & holder before purchasing.

What is Solar Fuse? 

فتيل الطاقة الشمسية is an overcurrent protection device (OCPD) designed for DC photovoltaic circuits. When the fault current exceeds the rated threshold of the fuse due to قصر الدائرة, wiring error or reverse current generated by the parallel string, the fusible element automatically fuses and cuts off the circuit before the damage spreads to the component, كابل or inverter.

What is Solar Fuse Holder? 

Solar fuse holder is a mechanical and electrical enclosure used to attach the fuse to the circuit while providing cable terminals. In the outdoor photovoltaic environment, the main function of the fuse holder is to isolate the fuse from moisture, dust, ultraviolet radiation and corrosive atmospheric environment. The contact resistance, corrosion resistance and IP Rating of the fuse holder directly affect the long-term reliability of the system.

Types of Solar PV Fuse

String Fuse

String fuse is the main component of residential and commercial photovoltaic protection. It is installed at the positive/negative extremes of each parallel string in the مربع الموحد to prevent the current of the normal string from flowing back into the shaded string, that is, to prevent reverse current from causing damage.

النطاق المقدر: 1A ~ 30A, 600V ~ 1,000V DC

شكل عامل: 10 × 38 mm, 10 × 85 mm Cylindrical

المعيار المعمول به: IEC 60269-6 gPV

Inline Waterproof Fuse Assembly

The solar fuse and the fuse holder are pre-assembled into an integrated component in the weatherproof housing for the string wiring section at the front end of the junction box. Its rated protection rating is generally IP67 or IP68 and is suitable for roof, floor through-pipe installation or direct-burial applications.

Battery Bus and Midpoint Fuse

The battery bus and midpoint fuse are used in the نظام تخزين طاقة البطارية (BESS) supporting the photovoltaic array. The DC bus voltage can reach 1,500 V DC, and the expected fault current can exceed 80 kA. The fuse and fuse holder with corresponding high breaking capacity are required.

Fast-Acting Semiconductor Fuse

Ultra-fast fuse is used to protect the input stage of الحد الأقصى لتتبع نقطة الطاقة (MPPT) inverter and power electronics. Its role is to complete the fault clearing before the semiconductor junction temperature reaches the destructive threshold. Under this condition, the response speed of the standard slow-blow gPV fuse is not enough to provide effective protection.

Types of Solar Fuse Holder

Inline Waterproof Holder

Generally, it is a cylindrical two-part screw-together shell, which accepts a standard 10×38 mm or 10×85 mm fuse, and is usually rated as IP67 or IP68. The cable inlet is sealed by a Compression cable gland (PG thread or metric thread). It is suitable for the group cascade protection section of the roof system before reaching the confluence box.

Key selection points: 

• Outdoor installation protection level must be ≥ IP65; iP67/IP68 should be selected for the wet or water risk area.
• The shell material is UV-Stabilized Polycarbonate or Nylon.
• Cable cross-section compatibility range: usually 4 mm² to 10 mm² (AWG 12 ~ 8).

Panel-Mount/Combiner Box Holder

It is generally used for DIN rail or لوحة الدوائر المطبوعة (PCB) installation inside the combiner box and re-combiner box to compactly accommodate multiple fuse components, usually directly integrated into the terminal block assembly of the junction box.

Key selection points: 

• مواد الاتصال: Silver-plated copper is preferred in high maintenance frequency environment, which is better than Tin-Plated Copper.
• Finger-safe/touch-proof design (IEC 60529) compliant, suitable for non-professional electrician-contacted junction box scenarios. 
• Equipped with fuse indicator window or blown-fuse indicator for quick visual fault diagnosis.

DIN-Rail Mounted Holder

It is generally a buckle-installed fuse holder for indoor or in-box DC distribution board. It is common in utility inverter room and DC bus protection components of battery system, usually suitable for larger fuses such as 14×51 mm or 22×58 mm.

Spring-Clamp/Ferrule Holder

A tool-free insertion and extraction fuse holder is used for a high-density confluence array with high maintenance turnaround time requirements. The spring contact can maintain a stable and consistent contact pressure on the fuse end cap no matter how the spring contact expands and contracts under the thermal cycling condition.

Integrated Fuse Block مع متعدد القطب

Multi-position fuse block can accommodate 6, 12 or 24 fuse positions on a single DIN rail. The standard configuration of utility-class junction box. Each location is protected by an independent fuse, and Inter-Position Isolation prevents the spread of cascading faults.

كيف Match Solar Fuse with Fuse Holder? 

The specification mismatch between the fuse body and the fuse seat is one of the main reasons for the on-site failure. The following compatibility matrix can be used as a preliminary checklist:

It is necessary to confirm that the current rating of the fuse holder is equal to or higher than the rated current of the fuse: if the 20A fuse is loaded into the 15A rated fuse holder, even if the fuse itself has never been fused, the contact terminal of the fuse holder will also accelerate aging failure due to continuous overheating.

The following 7 selection points completely distinguish reliable installation from on-site failure.

نقطة 1: The fuse is selected according to the string parameters, not the inverter parameters.

Solar DC fuse must be selected based on the string short-circuit current, not the input rating of the inverter. According to IEC 62548: 

• القيمة الدنيا: In ≥ 1.25×Isc
• أقصى: In ≤ 1.56×Isc
• Hardness upper limit: In ≤ component maximum overcurrent protection rating (IOCPR, printed on the back of the component nameplate) 

مثال على الاختيار: component Isc = 10.5A → minimum fuse = 13.1A, maximum fuse = 16.4A, selection result: 15A gPV fuse. If IOCPR = 15A, then 15A selection is valid.

نقطة 2: The rated current of fuse holder must be higher than that of fuse. 

The continuous rated current of the fuse holder must be at least one standard step higher than the rated current of the fuse. 15A fuse should be equipped with a fuse holder with a rated current of at least 20A. This ensures that the fuse seat contact terminal will never become a thermal weak point in the circuit.

نقطة 3: The DC voltage rating of fuse and fuse holder must be independently verified separately.

Solar fuse and fuse holder have their own independent DC voltage ratings. The fuse with rated 1,000 V DC is loaded into the fuse holder with rated 600 V DC. The combination formed does not conform to the specification, and the arc clearance distance inside the fuse holder is insufficient, which has potential safety hazards. The datasheets of the two components must be checked separately.

نقطة 4: Select the protection level according to the installation area (المنطقة), rather than judging by outdoor generally.

نقطة 5: ملابس حرارية derating should be considered in high temperature environment.

Photovoltaic fuse and its fuse holder are subject to heat derating constraints. In the tropical climate, the ambient temperature in the roof confluence box can reach 60℃. At this time, the fuse rated 15 A continuous current may need to be raised to 20 A to maintain the equivalent effective protection threshold. Be sure to check the derating curve provided by the manufacturer.

نقطة 6: Select the contact material according to the environmental conditions, not only the cost.

القصدير-pمتأخرا cOpper contact: It is suitable for installation in dry, low humidity and temperate climate with low cost.

الفضةpمتأخرا cOpper contact: This is mandatory for coastal, tropical, industrial environments, or any scene where sulfurous compounds or salt fog are present. The resistivity of silver oxide is much lower than that of tin oxide, which can keep the contact resistance stable during decades of operation.

In order to save a few cents of the contact material cost of each fuse holder in harsh environments, it is the most expensive False Economy in the design of photovoltaic systems.

Point 7: Planning maintenance accessibility from the design stage.

A solar fuse holder that needs to dismantle the entire header to replace the fuse must result in a long downtime. Specification requirements should be clear: 

• For the junction box with high number of strings, front-access or tool-free spring-clamp fuse holder is selected.
• For junction boxes without remote monitoring, the blown-fuse indicator (neon or LED) is configured. The laminated schedule is pasted on the inner side of the confluence box cover that indicate the string number and rated value corresponding to each fuse.

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