Electrical pathway intermittent fault detection
Testing to detect intermittent electrical pathways is described. Applied currents may be reversed to fully test all components of a workpiece. Various testing methodologies may be employed. These methodologies may include Time Domain Reflectometry (TDR), mechanical agitation, dark current/voltage testing, (dark IV), i.e., electrical testing of a workpiece using applied electricity, and thermographic imaging, e.g., infra-red thermal imaging. The sensed voltage during agitation may be compared to a benchmark voltage to determine whether or not an intermittent failure exists.
1. A method of testing an electrical pathway of a photovoltaic laminate comprising:
applying a monitoring voltage in a forward bias direction to a first photovoltaic laminate electrical diode connection between photovoltaic cells and measuring observed voltage at the first photovoltaic laminate electrical diode connection;
applying the monitoring voltage in a reverse bias direction to the first photovoltaic laminate electrical diode connection between the photovoltaic cells and measuring observed voltage at the first photovoltaic laminate electrical diode connection;
when applying a monitoring voltage in the forward bias direction, applying mechanical agitation to the first photovoltaic laminate electrical diode connection at a known frequency; and when applying a monitoring voltage in the reverse bias direction, applying mechanical agitation to the first photovoltaic laminate electrical diode connection at a known frequency; and
comparing measured observed voltage in the forward bias direction with applied voltage in the forward bias direction; and comparing measured observed voltage in the reverse bias direction with applied voltage in the reverse bias direction and, based on each comparison, determining if a diode failure is present at the first photovoltaic laminate electrical diode connection.
2. The method of claim 1 wherein the observed voltage when applying voltage in a forward direction is an alternating voltage.
3. The method of claim 1 wherein the observed voltage when applying voltage in a forward direction is a stable voltage.
4. The method of claim 1 further comprising:
when applying a monitoring voltage in the forward bias direction, applying mechanical agitation to the first photovoltaic laminate electrical diode connection at a first frequency; and when applying a monitoring voltage in the reverse bias direction, applying mechanical agitation to the first photovoltaic laminate electrical diode connection at a second frequency.
5. The method of claim 1 wherein the observed voltage when applying voltage in the forward direction is an alternating voltage alternating at a first frequency and wherein measuring the observed voltage at the first photovoltaic laminate electrical diode connection is conducted at a sampling frequency, the sampling frequency higher than the first frequency.
6. The method of claim 4 wherein observed voltage at the first photovoltaic laminate electrical diode connection when applying voltage in the forward bias direction and the reverse bias direction is sampled at a frequency larger than a frequency of the applied voltage in the forward direction and the reverse direction.
7. A method of testing an electrical pathway of a photovoltaic laminate comprising:
applying a monitoring voltage in a forward bias direction to a first photovoltaic laminate electrical diode connection between photovoltaic cells at a first frequency and sampling observed voltage at a second frequency at the first photovoltaic laminate electrical diode, the second frequency higher than the first frequency;
applying the monitoring voltage in a reverse bias direction to the first photovoltaic laminate electrical diode connection between the photovoltaic cells at a third frequency and sampling observed voltage at a fourth frequency at the first photovoltaic laminate electrical diode, the fourth frequency higher than the third frequency;
agitating the first photovoltaic laminate diode connection at an alternating frequency while applying the monitoring voltage in the forward bias direction at the first frequency; and
comparing sampled observed voltage in the forward bias direction with applied voltage in the forward bias direction; and comparing sampled observed voltage in the reverse bias direction with applied voltage in the reverse bias direction and, based on each comparison, determining if a diode failure is present at the first photovoltaic laminate electrical diode.
8. The method of claim 7 wherein the first frequency and the third frequency are the same and the second frequency and the fourth frequency are the same.
9. The method of claim 7 further comprising:
agitating the first photovoltaic laminate diode connection at an alternating frequency while applying the monitoring voltage in the reverse bias direction at the first frequency.
10. The method of claim 7 wherein the first photovoltaic laminate electrical diode connection between photovoltaic cells is in a potted junction box.
11. The method of claim 7 wherein the first photovoltaic laminate electrical diode failure is an intermittent electrical pathway.
12. The method of claim 9 wherein the agitating alternating frequency is less than the first frequency.
13. An electrical pathway intermittent fault detection device comprising:
an electrical sensor; and
a microcontroller,
wherein the microcontroller is configured to apply a forward bias current through an electrical connection of a photovoltaic workpiece for a first period of time and to apply a reverse bias current through the electrical connection of the photovoltaic workpiece for a second period of time, and
wherein the microcontroller is further configured to consider a frequency of vibration of a mechanical vibration generator applied to the photovoltaic workpiece by the mechanical vibration generator, and further configured to consider voltages sampled from the photovoltaic workpiece, the sampling conducted when the mechanical vibration generator is in contact with the photovoltaic workpiece, the sampling rate of considered voltages being faster than the frequency of vibration of the mechanical vibration generator.
14. The device of claim 13 wherein the workpiece is a photovoltaic laminate and the electrical connection resides in a potted junction box.
15. The device of claim 13 wherein the electrical connection has a maximum current, and wherein the forward bias current and the reverse bias current do not exceed the maximum current.
16. The device of claim 13 wherein the first period of time and the second period of time do not overlap and are each no longer than ten seconds and wherein the mechanical vibration generator is positionable below the photovoltaic workpiece.
17. The device of claim 13 wherein the mechanical vibration generator is mounted on a moveable control arm.
18. The device of claim 13 wherein the microcontroller is electrically coupled to a bus, the bus being electrically coupled to a power supply, a current voltage measurement module, and a movement control module.