power transformer toroidal transformer voltage transformer POWER TRANSFORMER Various Dyco Electronics' magnetics and power transformer products are used for military and commercial capabilities such as critical military applications, and with several companies coming from many areas of the railroad industry. A power transformer normally operates from either 60 Hz, or 400 Hz alternating current. Each tiny domain must realign itself twice during each cycle, or a total of 120 times a second when 60 Hz alternating current is used. The energy used to turn each domain is dissipated as heat within the iron core. This loss, called HYSTERESIS LOSS, can be thought of as resulting from molecular friction. Hysteresis loss can be held to a small value by proper choice of core materials.