Definition
A bypass diode is a Schottky or PN-junction diode integrated into a PV module junction box that protects the module from hot-spot damage during partial shading by providing a low-impedance current path around a shaded cell group.
How Bypass Diodes Work
- Cells in series; cells shaded reduces current available to the string.
- Without bypass: shaded cell reverse-biases, dissipating string current as heat.
- With bypass: current flows through diode around shaded cells; rest of module unaffected.
- Diode rated for full string current at low forward voltage drop (~0.5 V).
Key Takeaways
- Bypass diodes protect PV modules from hot spots during partial shading.
- Typical 3 diodes per 60-cell module (one per 20-cell group).
- Half-cell modules use 6 smaller diodes for finer protection.
- Diode failure can cause hot spots and fire risk.
- Modern inverters monitor for bypass diode anomalies via I-V scanning.
Frequently Asked Questions
3 commonly searched questions about Bypass Diode.
What is a bypass diode?
Diode in the PV module junction box that bypasses a shaded cell group, allowing the rest of the string to operate. Prevents hot-spot damage where the shaded cell would otherwise dissipate full string current as heat.
How many bypass diodes per module?
60-cell modules: 3 bypass diodes covering 20 cells each. 72-cell: 3 diodes covering 24 cells each. Half-cell modules: 6 diodes covering smaller groups.
Does bypass diode failure cause issues?
Yes. Failed diodes (open-circuit or short-circuit) cause module damage and potentially fire risk. Inverters detect anomalies via I-V curve scanning.
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