In alt.engineering.electrical Don Kelly wrote:

| Yes -you are shorting a part of the winding but the switching is a bit more
| complex than that so that short circuit currents are limited to reasonable
| values. It is a multistep operation with reactor switching. On-load tap
| changers are expensive and are generally limited to applications where this
| is absolutely needed (I have seen one where the tap changer was nearly as
| large as the transformer).

What about multiple parallel transformers, or at least multiple parallel
windings on the same core (on whichever side the tapping is to be done),
where the taps are stepped incrementally on each winding? Instead of a
shorted winding segment, you'd have windings of differing voltage in
parallel as each of the windings change their taps one at a time.

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wrote in message
...
In alt.engineering.electrical Don Kelly wrote:

| Yes -you are shorting a part of the winding but the switching is a bit
more
| complex than that so that short circuit currents are limited to
reasonable
| values. It is a multistep operation with reactor switching. On-load tap
| changers are expensive and are generally limited to applications where
this
| is absolutely needed (I have seen one where the tap changer was nearly
as
| large as the transformer).

What about multiple parallel transformers, or at least multiple parallel
windings on the same core (on whichever side the tapping is to be done),
where the taps are stepped incrementally on each winding? Instead of a
shorted winding segment, you'd have windings of differing voltage in
parallel as each of the windings change their taps one at a time.

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to
ignorance |
| by the abuse department, bellsouth.net is blocked. If you post
to |
| Usenet from these places, find another Usenet provider ASAP.
|
| Phil Howard KA9WGN (email for humans: first name in lower case at
ipal.net) |
------------
So you have a differential voltage producing a circulating current through
both windings leading to losses and heating due to circulating currents. In
addition, there would be shifts in the load sharing between the two
secondaries- with the possibility of overloading one of them. Also, you
still haven't solved the problem of switching the current from one tap to
another Note also to shift 2% you would have to make two 2% shifts, one on
each winding so that you are essentially doubling the work and tap changing
equipment while introducing other problems as Daestrom has indicated.
-

--

Don Kelly
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