Well and good, but your ESR argument in this case overlooks an important
point, as power is supplied from the transformer secondary the secondary
voltage drops.
1. The open circuit voltage difference is 60V (1950V to 1890V)
2. The full load difference is 10V (1880V @ 0.6A and 1870V @ 0.4V)
So as the higher voltage transformer supplies current (due to the voltage
differential) its loaded voltage will drop (due to its ESR) until it matches
the unloaded voltage of the lower voltage transformer. The reason for
including the current equalising resistors is to increase the ESR of that
transformer.
As the current increases the voltage drop across the equalising resistor/s
increases and the system reaches equilibrium.
*The voltage differential between the two transformers will now be a
combination of the unloaded low V transformer, the voltage drop across the
Equalising resistor, and (the now lower) partially loaded voltage on the
other transformer.
Now if the system is supplying power to an external load, the overall
dynamics improve as the fully loaded voltages of both transformers are so
close.
----- Original Message -----
From: "Tom Rauch" <w8ji@contesting.com>
To: <amps@contesting.com>; "Firson Maryutenli" <firson@hotmail.com>; "Noel
Willis @ Access IT" <AccessIT@Bigpond.net.au>
Sent: Thursday, January 18, 2001 9:46 AM
Subject: Re: [AMPS] Two XFMR in parallel
> 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.
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|