compatibility, etc. Only combiner boxes that have gone through all these tests can be certified according to IEC 61439-2
enclosures, clearance and creepage distances, protection against electric shock, mechanical operation, dielectric properties, wiring, operational performance and function, etc. Once all the routine verification tests have concluded successfully, a routine verification report is signed and included inside every single combiner box delivered to the customer.
Photo 2 – Assembly specialist during the prototyping phase Photo 6 – Combiner box wrapped in aluminum foil,ready for the dielectric strength test according to IEC 61439-2
Photo 3 – Discussion of improvements during the prototyping phase
• DESIGN VERIFICATION. This is one of the key areas that differentiates a good quality CB manufacturer from an unreliable, low cost one. The IEC 61439-2 mandates a series of tests to be performed on one representative prototype of each CB design. These tests include (but are not limited to): resistance to corrosion, resistance to UV, mechanical impact, degree of protection, clearance and creepage distances, dielectric properties, impulse withstand voltage, temperature rise, electromagnetic
• MANUFACTURING. Once the design has been verified against IEC 61439-2 and the prototype is formally approved, manufacturing documentation is prepared to trigger mass-production of the combiner boxes. Ideally this must happen in an ISO 9001-certified facility and the assembly process must be performed by workers with experience in the particularities of PV combiner boxes. The employees, the processes and the tools are periodically audited to ensure a fully compliant production. Once a combiner box unit has gone through the machining, assembling, wiring and marking phases it is handed to a different set of workers in charge of the routine verification. • ROUTINE VERIFICATION. One often misunderstood mandatory step in IEC 61439-2 is an individual test of every single unit manufactured, called routine verification. This verification evaluates the manufacturing process and looks for potential deviations and assembly errors, that is why it must be performed by workers different to those assembling or wiring the product. Routine verification includes (but is not limited to) the following tests: degree of protection of
Photo 4 – Setup for the temperature rise test according to IEC 61439-2
Photo 5 – Temperature rise test thermography according to IEC 61439-2
Photo 8 – Routine verification: employee performing a series tightening torque test according to IEC 61439-2
Photo 9 – Signed IEC 61439-2 routine verification report, included in every combiner box delivered to the customer
• ACCEPTANCE SAMPLING. As part of ISO 9001 and in order to fulfill the quality standards expected from a premium combiner box manufacturer, a statistical sampling (i.e. outgoing batch inspection) is performed on a subset of every combiner box production batch right before shipping it to the customer. This closes the feedback loop to ensure a continuously-improving designto-manufacture process for PV combiner boxes.
Conclusion
Photo 7 – Routine verification: employee performing a series dielectric strength test according to IEC 61439-2
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The background and concepts explained above are meant to illustrate the functions of combiner boxes, highlight the importance of CBs as a key BoS component in a PV plant and describe the behind-the-scenes development of a CB until it is ready for shipment to the customer. We hope that this educational material will be useful in the decision-making process of selecting a suitable combiner box, given the time and cost pressure that drives nowadays PV business. EQ INTERNATIONAL July/August 12
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