Electrical Considerations: 50 Years of the Engineers Newsletter

When joining Trane in 2000, with a background in electrical engineering, I found the Engineers Newsletters helpful in expanding my knowledge in the HVAC realm. The content was educational, timely, and well thought out with just enough technical detail to point me in the right direction and kick start my learning. It is an honor to be an EN author myself—having now authored or co-authored three newsletters. I hope to help Trane continue this goal of concise, timely education for many years to come.

Though not a primary topic, there have been eleven past newsletters particularly focused on electrical issues. Some introduce new technologies, for example; “Brushless DC Motors: Setting a New Standard for Efficiency” and “Adjustable Frequency Fan Speed Control” (ENEWS-12_10). Most others focus on two complex and often misunderstood topics; short-circuit current rating and harmonic distortion.

Short-circuit current rating (SCCR), first discussed in 1998, has an impact on equipment design and specification and is a prime example of a general topic where widespread education is needed. Due to evolving codes, we continue to follow this topic and provide yet another update as SCCR is the focus of the March newsletter.

• Short-Circuit Current Rating Refresher
• Short-Circuit Current Rating Update
• Protecting The Electrical Distribution System: Short-Circuit Withstand Ratings Demystified

Electrical harmonic distortion caused by solid-state power converters such as variable frequency drives, first discussed in 1985, is another topic with broad reaching implications for the HVAC industry. As the demand for higher energy efficiency and lower peak energy from our systems and equipment increases, the need to optimize operation of motors has prompted the inclusion of more power converters (e.g., VFD and EC motors) for finely controlled variable speed operation. These power converters necessitate careful design of the electrical system as they become a higher portion of the building's power consumption. Past newsletters offer informative background of the topic and best practices to mitigate possible issues.

A hidden gem in this area is “How VFDs Affect Genset Sizing”. Often overlooked because of its title, this EN not only addresses the important issue of generator sizing with VFD loads but serves as a wonderful background on the fundamentals of how VFDs work as well as the how and why of their less than desirable effects on the electrical distribution system.

• A primer for non-electrical engineers: Harmonic Distortion in Electrical Systems
• How VFDs Affect Genset Sizing: Appearances Can Be Deceiving
• Electrical Interference… A-C Inverters & Utility Lines (ENEWS-14_10)

I hope that the steady flow of quality Engineers Newsletter content has been helpful to increase your knowledge and make your job a little easier. It certainly has for me!

Thanks for reading and if there are topics (new or old) that would be helpful to address in future issues, please let us know!