I have posted the schematic of a power supply
as analyzed by LTspice so that the effects of
even small changes can be seen. The schematic
reveals the use of a stepstart scheme.
When specifying a power transformer, the usual
specs given to the manufacturer are primary
voltage/frequency, the secondary voltage and
current, the load (resistive, choke-input DC
supply or capacitor-input DC supply, etc.),
regulation, and probably some physical attributes
such as maximum size and/or temperature rise.
You will be given in return a transformer that
meets your steady-state specs. But for the kind
of detailed transient analysis that Spice allows, you
need all of the items I previously asked for. These
are shown on the schematic I posted. If you don't
have the items you can guess at the transient
performance, or follow some old wives' tales, or
do whatever seems expedient at the moment.
Without such examination the transient performance
(what happens at turn-on, load application, etc.)
will be unknown. If you don't care, then of course
you may skip the analysis.
The posted schematic is for a device that needed
low ripple on the output and delivered a bit over
one kilowatt of RF power from some solid-state
devices. I was trying to extrapolate it to a ham
rig supply for 1800 volts and 600 mA. I have
some data coming in but thought some of the
engineers/technicians who read this stuff might be
able to give us a headstart.
The schematic and its annotated transient response
are at
http://tonnesoftware.com/temporary/48V40A.gif
Note it is 1280x1024 in size, about 48 kB.
- Jim Tonne WB6BLD
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