Rectifiers Overheating

Q. We currently have a situation with our high voltage rectifiers overheating. We have 4 chrome lines. Each Chrome line has 4 rectifiers on each line. We plate solid rods that very in size from 12.5mm-25mm. Our chrome line #4 (10years old) is giving us our main issue with heat. The rod size that is ran down this line consists of 18mm, 20mm, 22mm, 25mm. A quantity of 20 rods are ran at one time. Our rectifiers are on a platform and the legs on our rectifiers are about 4" tall, this is where the fan is that draws the air up through the rectifier to cool it internally. The main problem is they are drawing warm to hot dirty plant air through the rectifier and not cooling them properly. Can you give me any alternate cooling sugestions for our rectifier issue? We really don't want to purchase all new rectifiers due to the cost.

A. Heat in the plating area is a common enemy. It affects everything including the coating performance if the bath or the rectifiers get hot. It can also lead to everything heating up at the plating line and eventually racks and parts begin to over heat. Sometimes bussing and tooling are inadequate and the heat generated at the plating tank can be transferred back to the rectifiers, causing lots of problems. It might be beneficial to bring in an expert at some point if you are not able to resolve this by other means.

It's not uncommon to see this in plating shops. Dirt and debris can find it's way in thru the air intake openings. Most air cooled units use expanded metal screens with quite large holes. Designers of course more concerned about the equipment running cool than screening out solid particles. I'll send a couple pics of a shop I recently did some consulting work for. They had similar problems... and as the photos show, this kind of electronic gear is easily neglected.

Quick fix? There are a few. If you are unable to change the environment around your power supplies, you might be forced to replace the air cooled units with water cooled. Short of changing cooling systems on the current units or buying new water cooled units, I would probably recommend having a fabricator outfit the bottom (intake openings) of your rectifiers with a bracket or framework to hold a flexible air filter. This material comes on a roll or in precut sections. The operator can simply pull out the old and pop in a new piece, or possible wash the old filters out and reuse. You can buy air filter material in numerous grades. This filter would function much the same as the air filter on a home heating & air conditioning system. Be careful to use the appropriate type of filter material that captures most particulate matter but will not restrict the air-flow.

Secondly, Its important to keep the "heat sinks" clean. These are the silver, iridescent yellow or nickel plated coolant blades inside the rectifier bussing near fuses and diodes. This equipment helps to dissipate heat. A thin coating of dirt on these can reduce the cooling efficiency by more than half. A third suggestion is to study the options of bringing in some additional cool air into the space that houses your power supplies. You could do this in several ways, if you have a basement, creating an updraft system by selectively opening up the floor and bring air vents up from the basement. This can also be accomplished by venting in cool air from outside to the area by way of flexible industrial tube vents from above the rectifiers... You could also go directly into the rectifier cabinet with a rigid cold air vent and draw cooler air in from above the units avoiding the floor altogether. In some hot climates some shops actually bring in outside air through a filtered air make up system avoiding using shop air all together.

A forth suggestion might be to build an enclosed room around the units and air condition the space, or at least erect a wall between the power supplies and the plating line. This is actually a common design practice we've used in designing new plating facilities for many years now. Separating sensitive electronic gear from the shop environment will add years to the life of the equipment.

I can find out what the filter material is called and who might supply it if you need further assistance.

Finally, plating rectifiers should be on a routine maintenance schedule and periodically be shut down, inspected, cleaned, vacuumed out and wiped down on the inside as well as having the meters or digital readouts checked under a "load" to confirm accuracy. This is a good opportunity to check the rectifiers for "ripple" and other general conformance issues.

I would like to hear more about your process and production concerns if you want to discuss, please feel free to contact me anytime.

Good Luck,

Randy Taylor