> Has nobody heard of "Current equalising resistors", but I guess this
> principle is only used in the domain of solid state amplifier construction
> :) One suggestion is to place a low value resistor (couple of ohms - use
> ohms law) in series with one secondary line from each transformer with a
> suitable wattage rating. Sometimes a resistor is placed in each line to
> lower the wattage rating required. The principle is that as the current
> increases in one transformer (the higher voltage one as it tries to push
> up the lower voltage one) the voltage drop across the resistor will
> equalise the load between them. Using ohms law you can work out what a
> suitable resistance will need to be at full load for each.
The thing simplifies to the ESR of the transformers powered by the
open circuit voltage difference.
Say we have two 20 ohm ESR transformers in parallel with a 100
volt difference in open circuit voltage.
The dissipation will be 100 volts across 40 ohms, or 250 watts. 250
watts minimum continuous dissipation is significant dissipation
even in a transformer (pair) rated to deliver 2 kilowatts of load
power. Just picture the heat of a pair of 125 watt light bulbs in an
enclosed area the size of the transformer.
73, Tom W8JI
w8ji@contesting.com
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