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How to Build a Bridge Rectifier for an A/C Welder

A/C welders use a transformer and bridge rectifier to create a high-current DC circuit used to weld metals. The bridge rectifier converts the AC power of the transformer to DC power. Building a bridge rectifier for this type of application requires knowing what the short circuit current is for the transformer. This is important because the diodes of the rectifier must be able to handle this current level for an extended period of time.

Things You'll Need

Four high current power diodes
Diode heat sink
Heat sink compound
Mounting screws
Screwdriver

Instructions

- 1
  Determine the short circuit current of the transformer. This can be found by contacting the transformer manufacturer or checking the welder documentation. Choose power diodes which have a higher current rating than the short circuit current.
- 2
  Connect the negative terminal of diode #1 to one of the two wires from the secondary side of the transformer. This splice will be called node "A." Connect the positive terminal of this diode to the positive welding wire. This splice will be called node "B."
- 3
  Connect the positive terminal of diode #2 to node "B." Connect the negative terminal of this diode to the second wire from the secondary side of the transformer. This splice will be called node "C." Connect the positive terminal of diode #3 to node "C." Then connect the negative terminal of diode #3 to the negative welding wire. This splice will be called node "D."
- 4
  Connect the positive terminal of diode #4 to node "A" and connect the negative terminal of this diode to node "D." Once connected, lubricate the heatsink with heatsink compound. This will help the diodes transfer more heat to the heatsink to protect the diodes from overheating. Secure each diode to the heatsink using mounting screws.

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