Started with a rat nest. One of the worst excuses for cabling and strapping I have ever seen. The cable block was too small or the cables where to big. What was the result of the rats nest? FIve of Six 600Volt Cables running at 300+ amps driving an electro magnet whose intended purpose is to adjust the main field of the supercon magnet real time during a scan. The very cables driving the electromagnet become magnets themselves. This causes them to flex when they are being driven. The end result after five years was five of the six cable where damaged. As seen in the picture one was cut all the way through. That would be bad enough, and one would think an 0 gauge wire would ok. Since they were terminated at the gradient coil (electromagnet) and the circuit measured open, coils bad. I inspected the cables, As seen in the picture before I pointed out the cut cable. Other than messy, all looked intact. Almost cost my customer $150,000. The manufacture agreed with my troubleshooting, the two National Specialist agreed with my troubleshooting, and the customer agreed with my troubleshooting. Yet something still bugged me. I continued asking questions. Discussing the problem. And an engineer I had never met in my life, who also agreed with my troubleshooting, almost mentioned in passing, that 20 years ago, he had seen a gradient coil end up being broken cables right where the cables transition from horizontal to vertical. I went back into the magnet and penetrating the insulation of the cables with my probes. I measured them right at the coil 0.04 Ohms., Funny how not giving up, discussing things, and taking one last look after every one else had thrown the towel in. Funny how just trying one last time things that were going very very very wrong, are suddenly right again. After a week of being hard down, concerns that the customer may not repair it. too many hours to count...but I will because thats how I get paid. By the hour. From doomsday to a new day for less than $100 in parts.
Posted on: Fri, 21 Nov 2014 06:50:54 +0000
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