Historically, the mechanical components of the fan drive system, specifically the right-angle gearbox, have been the largest maintenance issue for cooling tower installations. Gearbox failures, oil leaks, oil contamination, failed drive shafts, misaligned drive shafts, and excessive vibration are all significant problems related to this type of fan drive system.
A traditional cooling tower fan drive features a right-angle gearbox mounted under the fan, powered by a drive shaft attached to an induction motor. Gearbox failures, oil leaks, failed drive shafts, misaligned drive shafts, and excess vibration are all significant problems related to this drive system.
The Baldor Reliance Direct Drive Cooling Tower Permanent Magnet (CTPM) technology's features and benefits have been embraced by the industry. These include the following:
Reduces energy use
Reduces overall tower stress through the soft start capability
Removes alignment issues
Removes mechanical rotating equipment
Increases reliability
Decreases noise levels
Decreases yearly maintenance
Decreases vibration levels
Decreases ingress of contamination due to trickle current during idle periods
Incorporates anti-windmilling option during idle periods
Increases safety by enclosing all rotating equipment inside the tower.
Many of the problems associated with cooling tower maintenance and reliability are solved with the CTPM motor design. The relatively high speed gear input shaft, which typically runs at 1750rpm, has been eliminated. The CTPM direct drive motor runs at the typically slower fan operating speed, in the range of 147rpm to 382rpm.
Vibration and noise concerns have been minimized. The driveshaft and associated disc couplings have been removed, thus eliminating problems associated with misalignment, natural frequencies, or driveshaft delaminating. The right-angle spiral-beveled gearbox has been removed. Difficult maintenance problems associated with changing the oil, proper oil fill levels, contamination of the oil, oil leaks, and gearbox failures are no longer a concern.
New motor technology has led to an alternative solution, the direct drive of cooling tower fans. PM motor technology, combined with the finned, laminated frame design, now allows the construction of a low speed, compact motor for use in place of the existing gearbox. Data obtained to date indicates this solution will eliminate problems associated with the right-angle gearbox and drive shaft design. By eliminating the gearbox, which is a significant source of loss in the system, improved system efficiencies can be realized.
Roman Wajda is engineering and business manager for the air handling industry for Baldor.
I would think the elimination of all of those mechanical parts mentioned would have a huge impact on reducing maintenance costs. Afterall, if cooling towers are like appliances, maintenance crews likely log hours fixing faulty gearboxes and drive shafts. I'm curious if other companies are offering similar permanent magnet technology (or other technologies) that could be leveraged for the same drive cooling tower applications with similar lower maintenance properties. That would seem like a big advantage.
Energy saving in all forms was big in 2011 and will be an industry focus in 2012. This includes all forms -- whether via permanent magnets and reduced parts counts, energy efficient motors, and energy harvesting. It's also interesting to note that what was previously regarded as something of a tree-hugging arena is now taken seriously well beyond the early adopters. Why? Three letters: ROI.
I'd add another factor to the drive for energy efficiency--increasing environmental regulations. In some areas, that's another impetus for pursuing energy saving initiatives and technology.
Speaking of "tree hugging", although the efficiency benefits of variable-speed drive and simpler mechanics are clearly good, and are to be applauded - there is a darker side to the technology choices described. The high tech Neodymium magnets used in this motor are made from relatively rare materials which are nearly 100% mined in China due to the bad environmental impact from mining them. see: http://spectrum.ieee.org/tech-talk/green-tech/conservation/update-china-and-rare-earth-minerals
While these high energy magnets are sometimes the only realistic choice where small product size is paramount (such as audio earbuds) - the large mass of magnets used in these big motors are a questionable choice. Most hybrid cars are currently using similar motors, causing great shortages of these rare materials, and creating an unstable situation with reliance on China's supply of them.
As proven in some EV's - with good engineering you can still acheive high efficiency and power density, and be much more environmentally responsible by designing systems that use variable-speed induction motors (like the GM EV1 car) or variable-reluctance type motors. These motor types require more sophisticated drive electronics, but use only conventional silicon iron and copper in their motors, and no permenant magnets.
Engineers have a big challenge these days to design products that are efficient and cost effective, but also environmentally responsible as well.
From the materials perspective, as well as the green perspective, the rare earth issue is an important point, Rob. What are the alternative materials for creating magnets with similar functionality?
The point I was trying to make was a little different - that there are ways of designing motors to have similar functionality to those described without resorting to permanent magnets or using exotic materials at all. While using high energy magnets makes acheiving high efficiency "easier", that may not be the most responsible decision. In this case, there are motors from a different division of the same company that prove this point: http://www.abb.com/product/us/9AAC171953.aspx
NOTE: I have no affiliation whatsoever with any motor company - I'm just pointing out that today's engineering choices need to include "environmental responsibility" as well as the other dimensions of design.
Just as it is "easier" to get high performance from a heat pump system using freon, but environmental stewardship has forced the industry to change to other refrigerants.
Of course, another equally valid design choice would be to develop or use magnets that have similar high performance that don't use these kind of materials. I don't think this magnet technology exists yet. Neodymium magnets have appropriate uses where there is no other way to make the product small enough, but his this case I believe that using them in a large stationary motor application is probably not the best choice.
Thanks for clarifying your point, Kevin. Engineering choices are certainly more complex than they used to be before green was a big concern. OTOH, there were always tradeoffs involved, and now another set of variables has been added to the mix. I think your point is well taken: instead of a different material for making magnets, an alternate to magnets altogether may be a better overall choice.
The IEEE article posted by Kevin points out that "rare earths" are a misnomer as they are in fact very common in the earths crust. In China the extraction process uses old technology. Should the Chinese withhold these elements, a free market would rapidly develop new and clean methods to supply them. In a controlled economy no incentives to cleanup the environment exist. Add the profit motive and new methods or alternative materials will rapidly be invented. China is discovering this idea and moves toward a free market while we in the US move toward a government controlled market. They will no doubt pass us economicly should these trends continue.
This is another good example of energy savings via variable speed drives (VFDs). VFDs are showing up all over the plant. The big driver is energy savings.
A minor point to start - I think you have the first and last pictures in the article switched.
I enjoyed the article but had to stop and think a bit (not a bad thing, by the way!). I was somewhat misled in my first reading by the early discussion of VFD and missed (a bit) the primary point of the author's presentation - the use of low speed motors (i.e. PM motors in this case) permits a greatly simplified mechanical system (i.e. no gear boxes, right angle drives, etc). Add that new simplicity (and I love simplicity!!) to a variable speed drive and you get some very compelling results.
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