Why is improper EMI grounding so common?
Despite their demonstrated benefits, variable-frequency drives (VFDs) have a tendency to generate electrical noise (EMI) and be susceptible to interference. In a recent article, Frank Bartos explains how drive design and installation techniques can minimize EMI. Here, he discusses the importance of proper grounding and bonding.
Proper grounding and bonding is a must to mitigate electromagnetic interference (EMI) in variable-frequency drives (VFDs) and electrical systems. Unfortunately, improper EMI grounding is common. Mike Olson, power & control sales manager-HVAC applications at ABB Inc ., suggests two reasons for this situation:
1. VFDs are the most EMI-prone devices that installers handle, and their routine grounding methods used with other devices are not always adequate for drives;
2. Many buildings in the U.S. don't have a good, solid common ground, placing one floor-or one side of a building-at a slightly different potential than the main ground connection in the basement. "All building grounds should be at the same potential, which is often not the case," Olson says.
Grounding effectiveness for electromagnetic compatibility (EMC) is enhanced by an added bonding component, says Olson. Electrical bonding connects metallic, non-current-carrying components at a location, placing them at the same electric potential.
Matt Murray, SEW Eurodrive 's corporate trainer, believes that proper grounding tends to be more of a problem in the U.S. than in Europe and other parts of the world. This comes, in part, from the U.S.'s relatively reliable power grid and fairly clean power, compared to other countries. It seems that belief in grid reliability is causing some electric equipment installers to not focus first on proper EMI grounding practices, says Murray.
"European equipment and drives come with extra EMI measures-and higher cost-due to generally less grid reliability," says Murray. "OEMs don't know where a system might end up being used when they're designing it. This is the main reason for the increased measure of EMI protection included in a system. It includes filters, output chokes, and importantly, proper grounding for EMC."
Another part of the answer is that, currently, there is no binding EMC regulation for electric drives in the U.S. As a result, not all equipment installers are fully aware of EMC requirements.
To read the entire article, " Electromagnetic Interference: What Users of Drives Need to Know ," visit www.controleng.com/archive under Dec. 2009.
Case Study Database
Get more exposure for your case study by uploading it to the Plant Engineering case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.
These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.
Click here to visit the Case Study Database and upload your case study.
Annual Salary Survey
In a year when manufacturing continued to lead the economic rebound, it makes sense that plant manager bonuses rebounded. Plant Engineering’s annual Salary Survey shows both wages and bonuses rose in 2012 after a retreat the year before.
Average salary across all job titles for plant floor management rose 3.5% to $95,446, and bonus compensation jumped to $15,162, a 4.2% increase from the 2010 level and double the 2011 total, which showed a sharp drop in bonus.