Welding Power Magnetics
Transformers and reactors for resistance, spot, seam, projection and stud welding equipment, and for the plant supply that feeds them.
High Current, Short Bursts, and a Duty Cycle That Drives the Design
Welding loads deliver very high secondary current in short, repeated bursts. The transformer is sized to its duty cycle, its secondary impedance shapes weld current, and the burst pattern shows up on the plant supply as voltage flicker and harmonic current.
We help welding equipment builders and plants with weld transformers, mid-frequency DC (MFDC) transformer-rectifiers, control transformers and supply-side reactors. Related: power quality magnetics.
Typical Welding Applications
- ■ AC resistance welding: Spot, seam and projection weld transformers fed by SCR contactors.
- ■ MFDC welding: Mid-frequency transformer-rectifier packages on robot guns and fixtures.
- ■ Stud and arc welding power sources: Main transformers, output chokes and auxiliary transformers.
- ■ Weld controls: Control power transformers and isolation for weld timers and robots.
- ■ Plant supply: Reactors and filters to limit the effect of welder bursts on other equipment.
Welding Magnetics at a Glance
| Component | Typical role | What to specify |
|---|---|---|
| AC resistance weld transformer | Converts line voltage to low-voltage, high-current weld power | kVA at stated duty cycle, primary voltage, open-circuit secondary voltage, taps, cooling |
| MFDC transformer-rectifier | Mid-frequency weld power at the gun | Inverter frequency, secondary current, duty, cooling water, mounting |
| Output / stabilizing choke | Smooths arc or DC weld current | DC current, inductance, duty cycle |
| Control transformer | Weld control and robot power | VA, inrush VA, voltages |
| Supply reactor or filter | Reduces disturbance on shared plant supply | Number of welders, burst pattern, supply data |
What to send for a fast, accurate quote
- Weld process and machine type
- kVA and the duty cycle it is rated at
- Primary voltage, phases and frequency
- Secondary open-circuit voltage and maximum current
- Cooling water flow and temperature
- Mounting, lead and terminal arrangement (a drawing or photo helps)
Need a Weld Transformer Matched or Replaced?
Send the nameplate, duty cycle and secondary data. We will route it to a manufacturer suited to the build.
Build a transformer spec sheet Contact usWelding power magnetics: common questions
How are resistance welding transformers rated?
They are rated in kVA at a stated duty cycle, and the resistance welding convention is commonly 50 percent duty. A transformer can deliver more than its rated kVA at a lower duty cycle and less at a higher one, so the actual weld schedule should be included with any request.
What is MFDC welding and why does it change the transformer?
Mid-frequency DC welding uses an inverter, typically around 1 kHz, to drive a transformer with a built-in rectifier. The higher frequency makes the transformer much smaller and lighter than a 60 Hz unit, which is why it can mount on a robot gun.
Why do welders cause lights to flicker in the plant?
Each weld draws a large current for a fraction of a second, and the resulting voltage drop across the supply impedance repeats with every weld. Larger supply transformers, separate feeders, or compensation equipment reduce the effect. Supply data and the weld pattern are needed to size a solution.
Can you replace a weld transformer from the nameplate alone?
Often, if the nameplate is legible and includes kVA, duty cycle, primary voltage and secondary voltage. Photos of the mounting, terminals and water connections help confirm a drop-in replacement.