Paul, many thanks for sharing that valuable resource!
After reading the information I can see why there is much more to be
considered than one would think. The SSR needs to be sized to handle a worst
case load and that case is not well defined at all.
The heat sinking requirements are far greater than any I have supplied with
past projects. In fact, I never considered the need for heat sink compound
when mounting a SSR on a .125" thick back panel. Too little thermal mass
in the panel and poor thermal coupling to the SSR pretty much tells the
story.
The other thought brought up by others of a big inductive kick when the
power supply is turned off was not considered either. When a big KAPOW event
happens you can be sure that maximum current is flowing through the SSR when
the fault trip shuts it off. Then a huge voltage transient causes the SSR
to fail in a shorted condition, defeating the whole purpose of a trip
detector circuit.
I guess this is what happens when an amateur does the design work; amateur
results!
Thanks to all for a very enlightening discussion!
73,
Gerald K5GW
In a message dated 2/10/2014 5:47:13 P.M. Pacific Standard Time,
elespe@lisco.com writes:
There is a wealth of information here worthy of reading which may further
understanding of solid state relays, the application, what they can and
can't do and the myth of zero turn on related to inductive loads
http://www.crouzet-ssr.com/english/faq.shtml
Paul K0UYA
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