SLIDE 38 Temperature Sensitive Paint
There are paints that change color depending on their temperature (thermochromic). There are both irreversible (which stay at the color they changed to at their highest temperature) and reversible (which change back to their original color when the temperature returns). In the case of irreversible, it is often a change in density of the same color, so the color darkens. They could be incorporated in the following manner:
Subset (Irreversible Thermochromic Paint)
The paint can be applied on assembly or prior to inspection to the potential hotspots (terminals on cables, studs on panels). If desirable not to introduce paint to the components, pads can be constructed with the thermochromic paint on the top and an adhesive backing. Prior to inspection, these pads can be applied to the potential hotspots. After the panel is powered up, then shut down, the cabinet doors are opened and the colors on the pads examined. Those that were hotter will have darker or different color than their neighbors in the same circuit. Comparison color charts can be made up that can be held against the pad in the panel to judge a maximum temperature reached. Photos can be taken with visible light color camera.
Pro’s:
1. No change to existing panels 2. No camera required to inspect – documentation with a visible camera only 3. Panels operated normally – no open panels, no personnel safety issues. 4. Geometry independent – camera same angles as with present inspection
Con:
1. Will change color only when absolute temperature exceeds threshold. A bad connection may not indicate at less than full current (lower temp). 2. Requires additional steps to add and remove pads 3. Temperature sensitivity may not have fine enough resolution to tell difference between a few °C. (ACTION) Need more research. 4. Need to have the pads made up. 5. If paint applied directly, then would need to pass approval to be permanently installed inside the cabinet. Also, would need to be stripped off and reapplied for each retest. 6. Requires shutdown of panel both before (to install the pads) and after (to read the results)
Subset (Reversible Thermochromic Paint)
The paint can be applied on assembly or prior to inspection to the potential hotspots, either directly, or via the pads described above. Panel replaced with temporary panel containing visible transmission windows. Inspection done while panel energized and color change is noted by comparing color of different phases of the same circuit. Done with visible camera for inspection or just documentation.
Pro’s:
1. No camera required to inspect – documentation with a visible camera only 2. Much more flexibility in obtaining appropriate visible windows than IR windows. 3. Transmission much higher through visible windows (closer to 100 %). 4. Less geometry dependent – visible windows can be larger to cover more angles than IR
Con’s:
1. Will change color only when absolute temperature exceeds threshold. A bad connection may not indicate at less than full current (lower temp). 2. Requires additional steps to add and remove pads 3. Temperature sensitivity may not have fine enough resolution to tell difference between a few °C. Need more research. 4. Requires temporary shutdown of panel while temporary panel installed or removed. May not be able to open panel quickly enough to catch change
Initial Trade Study – Solution Concepts
Temperature Sensitive Paint
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