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Re: Ballasting the secondary side of transformers



Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Bart,

Ballasting on either side should be equally effective at limiting the current. Of course, on the HV side, the inductance value needs to be the turns_ratio (n) squared times larger because it has n times the voltage to deal with and needs to limit the current to 1/n times the current on the primary. This assumes an ideal transformer between the LV and HV ballast points.

LV ballasting:      + smaller inductance needed, lower voltage stresses.
                          - larger current means larger guage.
- core is needed to get the inductance and saturation needs to be considered.

HV ballasting:      + smaller current.
                          - HV insulation needs to be considered.
                          - inductance needs to be n^2 larger.
- core is needed to get this larger inductance and saturation needs to be considered.

These are all of the plusses and minuses that I could think of. If others, maybe someone else could chime in and comment on what is said.

Gerry R.


Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Can someone please tell me why we are still ballasting on the LV side of Pigs and PT's? This should be easy enough to do for a fixed current limit. The costs associated with a LV ballast almost demands we do this. The LV side is starting to appear very silly to me at the moment. Granted, there are HV concerns, but is it really a big deal? I get the feeling LV ballasting is simply convenient. However, it is also expensive (unless one builds a ferrite ballast).

Just curious is anyone else has contemplated a high side ballast.

Take care,
Bart

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