The Docs

Welcome to the Power Magnetics Institute Blog. We are privileged to have these two gentlemen as part of our distinguished faculty to enlighten, elucidate and otherwise inform you, our readers on the art and science of transformers and reactors. While the two might appear to be the same to the uninformed eye, they are actually quite different in form, fit and function. That is true of the transformers and reactors as well!

Enjoy your reading, please leave us a comment or two, and come back often for the next installment!

Dean of Faculty
PMI Institute

Impulse (BIL) Testing Reactors & Transformers: A Short Explanation

Docta Reacta: Power Magnetics was in the news again recently, this time for BIL testing. In case you missed it, this is just a quick update on some news you may be able to use, intended to help you be smarter buyers of magnetics. If you want to read the article, check out the links below – including the one on the Institute Blog. Don’t miss the links to the photos[…]

New Impulse Testing of Power Magnetics Reactors Achieves Certification at 169KV

New Impulse Testing of Power Magnetics Reactors Achieves Certification at 169KV High-level capability provides significant safety testing margin to assure system performance TRENTON, NJ, February 25, 2015 – Power Magnetics, Inc. today announced its successful completion of an industry standard impulse test, whose certified results achieving 169 KVBIL*, validate the reliability of the company’s design and construction methods for building iron core harmonic filter reactors.  This capability allows engineers to[…]

Step Down Auto Transformers: Closely Coupled’ versus ‘Loosely Coupled’ Winding Configurations

Dr. Transformer: Picking up from the previous post on Step Down Auto Transformers: Eliminating Output Distortion, I promised to cover ‘closely vs loosely coupled’ windings. Magnetics designers commonly use the terms ‘closely coupled’ and ‘loosely coupled’ to describe winding configurations, and though they may know what the terms mean, they may not be understood by other engineers, including those who are responsible for applications using step down auto transformers. In[…]

Step Down Auto Transformers: Eliminating Output Distortion

Dr. Transformer: Today’s lecture on step down auto transformers is short and sweet: what most transformer designers do not know can hurt you, the specifier or buyer and have a negative effect on your application. There is an issue with step down auto-transformers that is neither readily obvious nor generally known to most transformer designers.  Stated succinctly it is that unless the ‘series’ winding is in a ‘closely coupled’ (low[…]

‘Docta Reacta’ Publishes e-Book on Harmonic Filter Reactors

Docta Reacta:  I am pleased to announce that I am publishing The Power Magnetics, Inc. Institute’s first e-book.  It is entitled “Understanding the Advantage In Power Magnetics, Inc. Medium Voltage Harmonic Filter Reactors.”  It is designed to help the reader, in particular, the OEM understand the advantages to the Power Magnetics design, construction and manufacturing methods used to produce what is rapidly becoming the “defacto” industry standard for medium voltage[…]

Cooling Considerations for CLR’s in NEMA 3R Enclosures

Docta Reacta: Current Limiting Reactors, also known as CLRs, are most frequently sold in NEMA 3R enclosures and used in some pretty demanding environments, usually coal fired power plants. First, let’s discuss clearances for the enclosure. In this case, clearances for reactors within enclosures are dictated by the voltage class, not cooling requirement. For 600 volt class, one inch of clearance is all that is required. Cooling considerations dictate ventilation[…]

Power Magnetics, Inc. Quality Statement

Power Magnetics is known throughout the power industry for supplying high quality premium custom designed transformers and reactors.  We thought you might be interested in our Quality Statement that guides the work we do and our relationship with customers.  We hope that when you consider your next purchase of a transformer, AC reactor or DC inductor, you will give Power Magnetics, Inc. serious consideration, especially in those applications where efficiency[…]

Design Criteria for Iron Core Reactors for Harmonic Filter Bank Applications

Prafessa Reacta with you today. The design criteria for harmonic reactors are driven by the harmonic spectrum provided along with current rating, inductance, temperature rise, taps and impulse rating. The following considerations apply equally to both the single phase harmonic reactor and the three phase harmonic reactor when used in harmonic filter banks. Harmonic filter reactor current ratings are typically based on the following considerations: The reactor core will not[…]

General Specifications for Iron Core Reactors in Harmonic Filter Bank Applications

Docta Reacta:  Continuing our discussion, I thought we should provide you with some of the trade-offs when using harmonic filter reactors in harmonic filter bank applications. The construction methods for trap reactors lend themselves to a substantial flexibility in specifications and ratings.  For filter bank applications, single phase iron core reactors are most often utilized because of the flexibility and inherently higher ratings.  Copper winding is frequently chosen when performance[…]

Iron Core Reactors for Harmonic Filter Bank Applications – Part 2

Docta Reacta: Here is more enlightenment and edification on the trade-offs between three phase reactors and single phase reactors, harmonic filter reactors if you will, when used in harmonic filter banks.  Iron core reactors can be designed as either single phase or three phase.  There are trade-offs for each reactor type summarized below.   It may appear that there is a bias towards single phase reactors, and certainly these is more[…]