Furnace & Rectifier Multi-Tap Transformers
Multi-tap and low-voltage, high-current transformers for SCR-controlled furnaces, and rectifier transformers for induction, plating and DC power supplies.
Transformers Built Around the Load, Not a Catalogue Rating
Furnace and rectifier transformers are almost always built to order. A furnace transformer may need several secondary taps to follow heating elements over their life, very high secondary current at low voltage, and a rating that accounts for SCR phase-angle control. A rectifier transformer is designed around its rectifier: pulse number, phase shift, and the harmonic heating it creates.
We help furnace builders, induction equipment makers and plants collect the data a manufacturer needs and get the transformer quoted correctly the first time. See the induction heating & furnaces page for application detail.
Typical Uses
- ■ Silicon carbide element furnaces: Multi-tap secondaries to raise voltage as elements age.
- ■ MoSi2 element furnaces: Transformers sized with SCR current limiting for low cold resistance.
- ■ Vacuum & resistance furnaces: Low-voltage, high-current secondaries with bus or water-cooled connections.
- ■ Induction power supplies: 6 and 12-pulse rectifier transformers.
- ■ Plating & electrochemical rectifiers: High-current DC supplies with phase-shifted secondaries.
Furnace & Rectifier Transformer Types
| Type | Typical use | What to specify |
|---|---|---|
| Multi-tap furnace transformer | Heating elements whose resistance changes | Element type and count, resistance new and aged, voltage per tap, number of taps |
| Low-voltage, high-current transformer | Direct resistance heating and elements | Secondary current and voltage, duty, terminal and bus arrangement |
| 6-pulse rectifier transformer | Single rectifier bridge | kVA, voltages, rectifier type, harmonic heating |
| 12-pulse rectifier transformer | Two bridges with 30 degree shift | Delta and wye secondaries, balance between secondaries |
| Interphase / smoothing reactor | Parallel rectifiers and DC smoothing | DC current, ripple, inductance, cooling |
What to send for a fast, accurate quote
- Load type: element data, or the rectifier and DC output
- Primary voltage, phases and frequency
- Secondary voltage(s), current and tap steps
- SCR control method (phase angle or zero-cross) if used
- Air or water cooling and ambient
- Existing nameplate and photos for replacements
Need a Furnace or Rectifier Transformer Quoted?
Use the transformer spec sheet and describe the element or rectifier data in the notes, or send the existing nameplate.
Build a transformer spec sheet Contact usFurnace and rectifier transformers: common questions
How many taps does a silicon carbide furnace transformer need?
It depends on how far element resistance is expected to rise over its life and how fine the steps should be. The element manufacturer’s ageing data and the furnace power requirement set the voltage range, and the tap steps are chosen to cover it. Share that data and the current tap settings for replacements.
Does SCR phase-angle control affect the transformer rating?
Yes. Phase-angle firing draws non-sinusoidal current with harmonic content and a lower power factor, which adds heating. The transformer should be designed for the controller type and the operating range, not only the nominal kVA.
What is the difference between a 6-pulse and 12-pulse rectifier transformer?
A 6-pulse transformer feeds one three-phase bridge. A 12-pulse transformer has two secondaries, usually delta and wye, shifted 30 degrees, feeding two bridges. The 12-pulse arrangement cancels the 5th and 7th harmonics at the primary.
Can you replace an obsolete furnace transformer?
Usually. A legible nameplate, photos of the terminals and taps, the element or rectifier data, and the physical dimensions are normally enough for a manufacturer to quote an equivalent or improved replacement.