When I had my old drake T4XC transmitter, about every 40th time I turned it
on.... it just went
click and turned on. The other 39 times it made a helluva thump noise inside
the xfmr! There was
NO step start on the outboard AC4 power supply. My conclusion was I hit a
zero V crossing aprx
every 40th time. The zero V cross SSRs caught my eye soon after that.
The SSR is just an on-off switch.......and so is a contactor. On a lot of
contactors, the contacts are field
replaceable and ditto with the solenoid coil. Unlike a relay, a contactor is
essentially two sets of contacts
in series...per pole. Any arc is split into 2 x arcs = zero arcs. They
open off fast due to the typ huge spring tension.
Of course you need one helluva lot of magnetism to overcome the spring tension.
Small stuff like P+B 40A relays
have next to nothing for spring tension, and contacts are prone to welding
shut.
I find it amusing that all our HVAC stuff at work still uses contactors. Sure
P+B showed an example of a 150 hp electric motor
run on 600V 3 phase..all using a huge mess of SSRs in series parallel.
Problem is.... it would be a trick to trouble shoot
and isolate any int problems...or hard faults.
Jim VE7RF
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