GTI was established by K.C. Retzlaff in 1948. It was operated as a proprietorship under the name of Precision Transformer located in Muskegon, Michigan, USA. In 1951, the company was moved to Grand Haven, Michigan and incorporated under the name Grand Transformers Incorporated. As a result of K.C.’s love for amateur radio and his interest in electrical “tinkering,” GTI has grown to become a ‘World Class Manufacturer’ of inductive components.

In 1956, construction was started at the present Marion Street site.  Over the years, there have been numerous expansions to support the company’s growth.

1973 brought in a change in management as K.C.’s two sons, Gerald and Gregory, purchased the company prior to the founder’s retirement.

Over the years, GTI has purchased several magnetics companies and consolidated operations into the Grand Haven location which expanded our product offerings and customer base.

Today, GTI is a well-known international manufacturer of custom and specialty inductive components providing products to many fortune 100 OEM’s.  GTI is ISO 9001 compliant, modern, and a testament to the dedicated service of our many associates, suppliers, and loyal customers.

February 8th, 2016 brings about a new chapter.  GTI has acquired New Hampshire-based Warner Power, a provider of engineered power conversion products and services.

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