G'day,

Recently I've been given a defect welding inverter for parts.

While stripping it, I noticed the low-voltage rectifier (an inverter is
basically a switchmode PSU, a grizzly-computer PSU) that rectifies the
low-voltage AC to DC before exiting the machine. It consists of 3
diodes of 100A/600V each (RURU10060, for anyone interested).

The question: could I use this for rectifying the output of an
AC-welder (transformer type) to DC? Or should I use full-bridge
rectification for that (the 3 diodes in the inverter were wired as one
bigger diode; as normal in switchmode PSU's). Commercial rectifiers for
welders that I've seen all use full-wave rectification, which makes me
doubt if my 'grizzly-diode' would work satisfactorily.

Hope anyone with an electronics+welding background can help here...

Grtz,

Peter Dingemans,
The Netherlands.

You could try it but your welder will run at half power and you will
probably lose a lot of the advantage of using DC. With the full wave
bridge, the voltage (and current) goes to zero for only a small portion
of the cycle and allows the plasma in the arc to continue. With your
half wave setup you will have 8ms of 'dead' time.

wrote:
G'day,

Recently I've been given a defect welding inverter for parts.

While stripping it, I noticed the low-voltage rectifier (an inverter is
basically a switchmode PSU, a grizzly-computer PSU) that rectifies the
low-voltage AC to DC before exiting the machine. It consists of 3
diodes of 100A/600V each (RURU10060, for anyone interested).

The question: could I use this for rectifying the output of an
AC-welder (transformer type) to DC? Or should I use full-bridge
rectification for that (the 3 diodes in the inverter were wired as one
bigger diode; as normal in switchmode PSU's). Commercial rectifiers for
welders that I've seen all use full-wave rectification, which makes me
doubt if my 'grizzly-diode' would work satisfactorily.

Hope anyone with an electronics+welding background can help here...

Grtz,

Peter Dingemans,
The Netherlands.

AC welders need to be used with AC rods. The reason is that the
current reverses and the arc may tend to extinguish while the current
is zero.

If you only use one diode to rectify AC, there will be a much longer
time that the current does not flow and the welder will not work as
well as it does as an AC welder.

Dan

On 29 Oct 2005 12:36:31 -0700, wrote:

G'day,

Recently I've been given a defect welding inverter for parts.

While stripping it, I noticed the low-voltage rectifier (an inverter is
basically a switchmode PSU, a grizzly-computer PSU) that rectifies the
low-voltage AC to DC before exiting the machine. It consists of 3
diodes of 100A/600V each (RURU10060, for anyone interested).

The question: could I use this for rectifying the output of an
AC-welder (transformer type) to DC? Or should I use full-bridge
rectification for that (the 3 diodes in the inverter were wired as one
bigger diode; as normal in switchmode PSU's). Commercial rectifiers for
welders that I've seen all use full-wave rectification, which makes me
doubt if my 'grizzly-diode' would work satisfactorily.

Hope anyone with an electronics+welding background can help here...

Grtz,

Peter Dingemans,
The Netherlands.


Using a single diode will cause DC to pass through the welding transformer
secondary winding. This will cause the core to saturate. This will cause the
fuse to blow.

Mark Rand
RTFM

Mark Rand wrote:

Using a single diode will cause DC to pass through the welding transformer
secondary winding.

How d'ya figure?

Kevin Gallimore

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