> See, I do need a schematic to be able to give you a precise answer! If
> you are switching the Primary of a transformer and your fuses between
> the SSR and the transformer are blowing, I will suspect quite a HIGH
> Back EMF :) SSR are notoriously bad in switching INDUCTIVE loads :)
It always takes more than a quick pulse of back EMF to blow a fuse.
Even fast-acting low-current fuses require many cycles of 60Hz energy
to fail, unless the overload is dozens of times the operating
current. Larger current standard fuses are worse.
Even more important, back EMF does NOT occur with a switch closing,
unless there is considerable contact bounce and the transformer is
unloaded or loaded very lightly.
> You might need to insert a capacitor of the proper value in PARALLEL
> with the transformer. This capacitor will act as compensation for the
> inductive reactance of the transformer presenting a conjugate match
> that will leave you with the pure resistance only.
That isn't true, except with specific load conditions. With a
resistive load on the transformer, the primary reflects a nearly
perfect resistance. With a capacitor input supply, the primary
normally reflects a current-leads-voltage condition at start up,
gradually changing to voltage leads current AFTER the capacitor
charges but ONLY while heavily loaded at operating voltage.
When lightly loaded, the power factor is nearly unity.
> Much in the way the antenna tuner works :)
Not at all. They are entirely different because the supply is a
dynamic system.
> This is common occurrence in SMPS design :) In a sense you have
> already provided this capacitor :) I think :) But is the value right ?
> or in the best location ?
In a SMPS, input capacitors are actually problematic for switches and
fuses because charging current increases inrush.
> The simplest things are proven the most complex one
Only when we over-complicate them needlessly.73, Tom W8JI
W8JI@contesting.com
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