E-mail for MF transformers        Isomatic factory


Isomatic designs and manufactures Medium Frequency resistance welding transformers (1000 Hz square wave input, DC output) in ISO H size integrated transgun style, supplementing the 50/60 Hz range.

For enquiries for medium frequency transformers: E-mail by clicking including delivery location so we can use an appropriate currency and estimate transport costs.


63, 80, 100 and 125 kW @ 20% ED

Fully encapsulated in epoxy resin

Fully protected rectifier assembly (IP 20)

Fast and convenient disassembly of the rectifier assembly.

Water cooled rectifier and transformer secondary.

Compact and lightweight

Patent pending

Compatible with the forthcoming International Standard, currently ISO CD 22829.

Prospective Customers can E-mail Isomatic by clicking on the Logo panel at the top of this page.

MF Transformer


Medium-frequency (MF) transformers are a result of recent advances in resistance welding technology. They are powered by a transistor inverter, supplying square wave AC 500 V @ 1000 Hz which is converted by the MF transformer to a low voltage high current AC. This low voltage AC current is rectified to DC by a diode block built into the transformer.

The higher operating frequency of an MF system allows efficient energy conversion using a smaller and lighter transformer. Other benefits with MF transformers used in portable and robotic welding guns are:

  1. The reactance of the welding loop only limits the upslope and downslope of the welding current, while the peak welding current in limited only by the welding loop’s resistance. The net result is again smaller transformer, especially when welding with large throat, high-impedance guns.

  2. MF welding is less demanding on the plant power system. The MF inverter draws balanced line current from all 3 phases and operates at a high power factor (0.9).

  3. With MF transformers the peak welding current almost equals its RMS value, which helps to obtain quality welds with no splash and constant strength even at lower pressure.

  4. The high frequency permits much faster – 1000 times per second - process control, which again results in better weld quality.

The only disadvantage of MF systems is the higher equipment cost, but recent technology advances permitted ISOMATIC to overcome even this problem and introduce the MIT line - the smallest and most efficient MF transformers on the market.


 Type MIT - 63 MIT - 80 MIT - 100 MIT - 125
 Secondary no-load voltage (Volts) 6.3 7.1 8.3 10.5
 Power rating @ 20% ED (kW) 63 80 100 125
 Secondary current @ 20% ED (kA) 10 11.3 12 12
 10 ms surge current (kA) 50 52 55 55
 Weight (kg) 14 14 15 17
 Colour Blue Green Grey Yellow
 Primary voltage
500 V/1000 Hz
 Weld current measuring coil
150 mV/kA

 Temperature monitors





140 degrees C

80 degrees C

60 degrees C


   - Water connections

   - Water flow

   - Pressure drop


R 1/4"

6 litre/minute, max. 30 deg. C

0.6 bar


H-size (106 x 150 mm)


245 mm


To view a drawing in PDF format, in a new window, click on the relevant link below:

MIT 63 (63 kW)

MIT 80 (80 kW)

MIT 100 (100 kW)

MIT 120 (120 kW)

Links to rest of Isomatic UK site:

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This page was updated and its HTML syntax checked on 23 July 2005 using BBEdit on an iMac  Apple logo.

Isomatic has a policy of continual product improvement and therefore reserves the right to change specifications, dimensions and appearance from that shown on this web page.

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