Delta-Star Electric was founded in Chicago in 1908 to manufacture devices required by the electrical industry in the generation, transmission, and distribution of electrical energy. Some of its early products included a complete line of high-voltage indoor and outdoor switches including disconnects, transfers, interrupters, and disrupters for single and group operation.
In 1950, Delta-Star Electric Company was purchased by H. K. Porter Company and was subsequently renamed the Delta-Star Electric Division of H. K. Porter Company. On October 13, 1959, H. K. Porter purchased Hill Transformer and moved it to Belmont, California. Shortly after the purchase of Hill Transformer, H. K. Porter built a transformer plant in Lynchburg, Virginia and became operational in 1962. In 1980, the Chicago plant was closed. Subsequent to the closure of the Chicago plant, the Delta Star name (without the hyphen) was used by the transformer plants in Belmont and Lynchburg.
On November 23, 1988, Delta Star was sold to the Delta Star Employee Stock Ownership Plan.
Delta Star is capable of constructing transformers that are 230,000 volts and below in both single and three phase ratings through 900 BIL rating. These units could include tap-changing equipment and are utilized in both utility and industrial applications. Utility applications include power, distribution, generator step up, UAT, grounding units, voltage regulators, and autotransformers. Delta Star's industrial transformers are used for secondary load centers, unit substations, distribution services, power substations, and hazardous locations.
Delta Star constructs mobile transformers that can be used for a number of different purposes, which include serving as temporary substations during emergencies or as a safeguard against power outages resulting from malfunctioning transformers. Additionally, mobile transformers are used in remote locations until permanent transformers are in place and for planning routine maintenance of permanent substations. Delta Star's mobile transformers can be built up to a capacity of 100 MVA rating and up to 230,000 volts. DSI can provide multiple voltage requirements for use on both the high and low sides. Additionally, load tap changer equipment can be installed for the secondary voltage regulation. All of the mobile transformers and mobile substations are welded to their trailers.