Spang Power Electronics designs and manufactures a wide range of dry-type specialty transformers to provide the voltage matching capability and unique application ratings required for the industrial marketplace.
Custom high voltage / high current transformers are available to satisfy production requirements. Spang designs dry-type transformers in 5 to 30 kV classes to step down power from the distribution voltage to any application voltage. Water-cooled transformers are supplied to accommodate most high current applications.
Furnace transformers are available to satisfy a wide variety of heating element characteristics. These custom transformers are designed to meet our customers’ system specifications and can be provided in single phase, three phase, and Scott-T connected power topologies. Transformer designs can be supplied as a core & coil only for customer integration or in a variety of enclosures with accessories such as tap switches and meters. Complete AC / DC power centers can also be provided including Spang SCR Power Controllers.
Silicon Carbide Heating Application
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-T Connected Transformers (Phase Changers)
Scott-T connected transformers (phase changers) offer a wide range of three-to-two phase transformation. They provide two, single phase outputs while drawing balanced power from a three phase input.
Applying Spang’s digital SCR technology and burst firing (zero crossover control) into the primary of the Scott-T transformer allows the application to run near unity power factor with less harmonics. This control method for the Scott-T power topology reduces the need for many course or fine tap adjustments during the production cycle typically required to yield a high efficiency.