FAQ

Potential induced degradation (PID) is a phenomenon that impacts the ions of a solar cell and results in the degradation of the output of that cell. PID can significantly reduce the power output of a photovoltaic (PV) module within the first year of operation, with power losses at the module level as high as 70% in the first 18 months. These module level losses can progress rapidly and become so severe that they affect the performance of an entire system.

Anti-PID method for Delta Inverters

• Operating timing and condition: During night time and without DC current present
• Implemented method: There is parasitic capacitance between a PV module and grounding node. After sunset when there is no DC current, Anti-PID function will be started after 30 minutes. The inverter will provide a small current to charge parasitic capacitance between the negative node of a PV module and grounding node to raise a positive potential. This helps in reversing the polarization effect which occurred during operation. This can assist in the faster recovery of the PV array affected by PID.
• Please consult your solar module manufacturer for more detail about the duration and criteria for performing this function.
• Delta inverter models with Anti-PID:  M15A_220, M20A_220, M30A_230, M50A_260, M70A_260, M125HV, M250HV

• Pro EL stands for Pro Electroluminescence imaging that is a method for routine On-site PV installation inspection, allowing the EPC and O&M companies to detect defective solar modules which causes degradation in electricity production performance.
• EL imaging relies on the same principle as a LED.  It applies a direct current to the PV module in a dark environment and measures the photoemission by means of an EL camera.  
• The wavelength of the photoemission of different solar cells will depend on their energy bandgap.
• For example: The photoemission wavelength of Crystalline Silicone(c-Si) is from 950nm ~ 1250nm (near infrared).

With a CCD camera and the EL mode activated, the light emission of the modules recorded by the camera can indicate defective modules that decrease energy performance.

• The Pro EL mode is integrated in the M125HV and M250HV inverter models.

Benefits of Pro EL-Mode in M125HV & M250HV

• Eliminates the need of a DC power supply
• Eliminates the change of the DC wiring
• One click to enable the function during day time
• Can supply DC current to max. 20 strings simultaneously
• Saves inspection time and cost

PV Arc Faults result from a failure in the intended continuity of a condutor.  When a conductor is interrupted and forms a spark, it will will produce light and a high amount of heat which can lead to fires and property damage.

Causes of Arc-Faults include:

• Damaged, pinched or abraded conductors
• Loose or separated connections or terminations
• Cracked or corroded solder joints in modules or other components

Delta's inverters will shut down automatically with the occurence of an Arc Fault, thus avoiding fires and property damage in the PV plant.

Following the UL1699B, the inverter trip time will be less than 2.5 seconds after the arcing is detected, it can occur faster depending on the situation.

Delta's inverter models with Arc Fault Detection feature include: M15A_220, M20A_220, M30A_230, M50A_260, M70_260, M100A_280, M250HV.