Bypass diodes are small components with a critical mission: protecting solar modules from damage caused by partial shading. When even a single cell in a series string is shaded, it can be forced into reverse bias, leading to hotspot heating and permanent damage.
Bypass diodes are connected anti-parallel across groups of cells within the module. Under normal operation, they remain inactive. When shading occurs and voltage across a cell string reverses, the diode becomes forward-biased and allows current to bypass the shaded section.
This prevents excessive heat buildup and limits power loss to only the affected portion of the module. However, it also causes a step or notch in the I-V curve, which technicians can detect during diagnostics.
Understanding diode behavior is essential for identifying shading losses, diagnosing diode failure modes, and interpreting string-level performance issues.
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