Any furnace that uses voltage other than standard commercial power needs a transformer. Whether for home or industrial furnaces, the transformer changes the voltage of the input power to a different voltage for use within the furnace.
How It Works
The input to the transformer connects to commercial power and goes through the primary winding--a coil of wires wrapped around a metal core. The primary induces voltage into a secondary coil, usually with fewer windings, to reduce the voltage.
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The reduced output voltage of the transformer goes to the control circuits of the furnace to perform the required electrical functions. That can involve temperature controls, timers and igniters.
A universal NEMA type-D furnace transformer for domestic use has an output voltage of 26.5 volts for an input of 120 volts. However, specialty transformers for custom or elaborate furnaces could have different outputs.
A typical universal type-D transformer measures 2 3/32 inches high by 2 5/8 inches wide by 2 3/16 inches deep. It comes with 9-inch, color-coded wires attached to the primary and the secondary.
Industrial high-performance transformers, used for induction heating processes, come with automatic cooling and several outlets for various loads. The transformers are available in single-phase, double-phase or three-phase input configurations for high-power operations.