[Milsurplus] Electrolytics then and now

[gl4d21a at juno.com]

<<<<"Getting back to electrolytic capacitors, there is some progress 
from
time to time.  I went to an IEEE meeting a few years ago where the
speaker was from a company that makes variable-speed motor drives,
which consist of a rectifier turning line power into DC followed by
a variable-frequency inverter producing AC to drive the motor.
The speaker mentioned that electrolytic capacitors were one of their
reliability problems.  They had worked with their supplier and learned
that the supplier had not anticipated the kind of ripple current that
the rectifier-inverter application causes.  Excessive ripple current
was overheating the capacitors internally, leading to early failure.
The supplier came up with an improved design featuring much larger
terminal bolts, to conduct heat to heavy busbars, and with a 
threaded boss on the bottom to allow the capacitor to be attached
firmly to a heat sink.">>>>

And thus were (re)born low ESR capacitors.  The first birth was due 
to the requirements of low voltage, very high current (remember TTL?) 
power supplies. but the technology did not seem to carry over to the 
higher voltage units until ASDs* came along.  Talk about engineers 
not learning form their predecessors.

73,
George
W5VPQ
*The industry accepted terminology, at least so far this week, is 
Adjustable Speed Drive.



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