To judge the reliability of solar inverter, we should focus on six dimensions: electrical performance, environmental durability, protection and safety, components and life, certification and testing, brand and after-sales, and give priority to the models with high MTBF, stable efficiency, strong protection, complete protection and uniform certification.
I. Core electrical performance (stable power generation+less loss)
1. Conversion efficiency (most intuitive)
Maximum efficiency: single-phase ≥95% and three-phase ≥ 98%; European efficiency (Euro)≥97%.
Low load efficiency: efficiency ≥90% under 20% load, avoiding large loss under light load.
Efficiency retention rate: after 1000 hours at high temperature and humidity (40℃/90% RH), the efficiency is ≥ 95% of the initial value.
MPPT efficiency: ≥95%, multi-channel MPPT is better, fast tracking and high accuracy when shadow/light fluctuates.
2. Output quality (no damage to equipment+compatible power grid)
Total Harmonic Distortion (THD): ≤ 3%, pure sine wave, smooth waveform without distortion.
Voltage/frequency stability: the output fluctuation is ≤ 2%, and the frequency is stable at 50/60 Hz 0.1 Hz.
DC component: ≤ 1% of rated current, so as to avoid damaging the power grid transformer.
Second, environmental adaptability (outdoor long-term resistance)
1. Protection level (waterproof and dustproof)
Indoor: ≥ IP20; Outdoor/roof: ≥ IP65; Coastal/harsh environment: IP66.
2. Temperature and humidity range (can withstand extreme weather)
Working temperature: * *-30℃ ~+60℃ * * Stable operation, no high temperature derating.
Humidity and heat: 40℃/90%RH for long-term operation, insulation resistance ≥ 1mω.
Salt fog resistance: it has passed the salt fog test of GB/T 2423.17, and is necessary in coastal areas.
3. Mechanical and anti-interference
Seismic/impact resistance: Through vibration test, solder joints and terminals are not loose.
Lightning protection: DC side ≥6kV and AC side ≥4kV surge protection.
Anti-interference: EMC meets the standard and will not be interfered by grid harmonics/lightning.
Third, the protection function (failure does not blow up the machine, does not hurt people)
DC side: overvoltage/undervoltage, reverse connection, insulation fault and overload protection.
Ac side: over-current/short-circuit, over-frequency/under-frequency, leakage current (GFDI) protection.
Core safety: islanding protection (power failure ≤100ms) and over-temperature protection (IGBT/capacitor over-temperature load shedding/shutdown).
Action requirements: protection point error ≤5%, and action time ≤ 0.5s..
Four, components and life design (determine how long it can be used)
1. Core devices (see brands and specifications)
Power device: IGBT/SiC MOSFET (Infineon/Mitsubishi/Starr) with junction temperature margin ≥20℃.
Capacitor: Long-life electrolytic capacitor/thin film capacitor (Japanese/Taiwan system), with design life ≥10 years.
Heat dissipation: active heat dissipation (low noise fan)/passive heat dissipation, full-load temperature rise ≤40℃, and enclosure ≤50℃.
2. Reliability index (quantitative life)
MTBF (Mean Time Between Failures): ≥ 200,000 hours for assembly and ≥ 400,000 hours for industry and commerce.
Annual failure rate: civil ≤4%, industrial ≤2%.
Design life: ≥25 years (matching the life of photovoltaic panel).
V. Certification and Factory Testing (Authoritative Endorsement)
1. Necessary certification (indispensable)
Domestic: 3C certification, GB/T 37408 (interconnection) and GB/T 37409 (safety).
International: IEC 62109-2, VDE-AR-N 4105, CE, UKCA.
2. The factory must test (verify reliability)
High and low temperature cycle, damp heat, salt spray, vibration, lightning strike, long-term full load, island protection test.
Third-party test report: data such as efficiency, THD, temperature rise and MTBF can be found.
Six, brand and after-sales (long-term protection)
Brand: Sunshine Power, Huawei, Goodway, Jinlang, SMA, Fronsius and other first-line manufacturers, with mature technology and fast iteration.
Warranty: ≥5 years for assembly and ≥10 years for industry and commerce, and extended warranty is supported.
Services: local after-sales, remote monitoring, quick maintenance, firmware upgrade.
VII. Quick Judgment List (for purchase/acceptance)
Efficiency: max ≥95%, Europe ≥97%, MPPT≥95%.
Protection: outdoor ≥IP65, working temperature range * *-30℃ ~+60℃ * *.
Protection: islanding, overvoltage, overcurrent, overtemperature and lightning protection are complete, and the action is ≤ 0.5s..
Device: IGBT/thin film capacitor+high quality heat dissipation, MTBF ≥ 200,000 hours.
Certification: 3C+IEC 62109+GB/T 37408 is complete.
After-sales: ≥5 years warranty, local service outlets.
