[AT] OT Cooling Electronics was Statistics In Tractor Manufacturing

[rbrooks at hvc.rr.com]

I’ve worked on industrial equipment for longer than I care to admit. Design specifications and real world operating conditions a very often two entirely different environments. When you design a system the designer is given operating condition that assume certain conditions, both ambient and environmental.   

  I’ve been called in on failures of VFD cabinets that were placed on next to the air handles in an plastics factory above 50 feet above the factory floor under a metal roof. Temperature on the catwalk was 130 degrees. The interiir of the drive cabinet was over 180 F. The customer could not under stand what the issue was. Same customer 600 hp drive failed on an extruder drive was in service for 18 months. No one ever changed the air filters on the cabinet cooling fans. They were so clogged you could not get 100psi air thru them. 

Drive cabinet on a tire recycling plant. NEMA 3R cabinet. Customer had the drive about 60 days. Drive failed. When I opened the cabinet it was full of water. Somebody ran the power line into the top if the cabinet with the wrong fittings


Bottom line is customers don’t always follow factory recommendations. It is not always the fault of the design engineer

Bob
  

Sent from my iPhone

> On Sep 22, 2019, at 10:08 AM, James Peck <jamesgpeck at hotmail.com> wrote:
> 
> They may have given up on trying to keep electrical cabinets cool by natural means. A couple of years ago  I encountered a US built mechanical servo press that had a chiller mounted up on a top platform and water/air heat exchangers inside the electrical enclosures. The temperature switches would shut the press down if the temperatures inside the electrical cabinets rose into the upper nineties. The fan motors on the heat exchangers would get some dirt from air in their bearings and bind up. The cabinet would overheat and the temperature switch would shut the press down with a fault.
>  
> [[Stephen Offiler] It's a reasonable default position to assume competence, but by no means am I trying to say there aren't many exceptions.  If you think about it, it's less reasonable to take the opposite position and default to the assumption of incompetence.  You'd have a hard time ever trusting anything.
>  
> [ Jack] Around 40 years ago I was involved with technical support of a product that used an early PLC mated to DC Drives in cut to length on the fly machinery. At room temperature of around 98 oF, it would start to miscount. In fact, you could put your finger on the chip where the calculations were being performed and burn it. A muffin fan blew air in the direction of the overheated chip but wires obstructed the flow.
>  
> I went to R&D and asked what the test results were that resulted in the 40 oC rating. They said that was a standard rating. After some more questioning by me, it was revealed that there had been no testing done.
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