[Amps] Equalising resistors with HV diodes

[peter.chadwick at Zarlink.Com]

Rich said:

>Without equalizing resistors, and provided that all of
>the rectifiers in a series-string have similar junction-capacitances,
>the reverse current is the same in each one.

To a point. IF the diodes all come from the same diffusion batch, it's
probable, although if the wafer is large, you can see generally see
differences from one side of the wafer to the other. Don't let anyone try
telling you that semiconductor manufacture really is well controlled - if
they do, ask why we need to do 6 sigma design.

When my employer had a diode/thyristor manufacturing line, I asked the guys
there: they felt that diodes from the same batch should be OK, but if
you're not sure, the use of equalising resistors has merit. Of course, they
were dealing with 2000piv 250 amp jobs seriesed up for electric trains -
and I don't mean the model in N gauge!

73

Peter G3RZP