Spang Power Electronics designs and manufactures a wide range of dry-type specialty furnace transformers to provide the voltage matching capability and ratings required by a variety of heating elements.

Furnace transformers are available in single, three phase and scott connected designs. They can be provided as core/coil units or in a variety of enclosures with accessories such as tap switches and meters. Complete AC power centers can also be provided including Spang SCR power controllers.

Silicon Carbide Heating Applications
Silicon carbide elements change resistance with age. In order to deliver full power over the resistance range, a means of increasing voltage over a two-to-one range must be provided. Spang designs multi-tapped transformers for these applications.

Typically, a transformer will have six coarse and six fine taps to provide a two-to-one voltage range. When the transformer is coupled with an SCR power control unit, the fine taps can be eliminated. With SCR control, the five coarse taps provide infinite voltage control over the entire two-to-one range with a high power factor (.80 or better).

Molybdenum and Graphite Heating Applications
Molybdenum and graphite elements generally are operated at lower voltages (approximately 50 volts) and higher currents. These elements change resistance with temperature.

For contactor or manually controlled heating applications, reduced voltage taps are required to avoid overloading the system during the cold elements’ low resistance stage. Typically, a transformer is designed with three or four secondary taps, depending on the size of the furnace. Since the current will be higher than nominal when each voltage is first applied, some oversizing of the electrical system, including the transformer, is desirable. For finer control, additional taps may be specified.

By incorporating a SCR power controller, a less complicated transformer is required. A Spang SCR power controller, with RMS current limit and soft start permits the furnace to be brought up quickly and safely without secondary taps.

Scott Connected Transformers - Phase Changers
Scott connected transformers (phase changers) offer a wide range of three-to-two phase transformation. They provide two phase outputs while drawing balanced power from a three phase input.