Morning Neville,
At 11:15 PM 9/1/2008, you wrote:
Here's something I find curious...when I connect a multimeter to the
electrodes on my 24V mains power unit I get a reading of
30V...???? How can this be so? Why doesn't it read 24V as stated
on the power adaptor? If it's complicated and/or lengthy at all,
don't worry about it for now.
I have to worry about it. You and likely others need to know.
Power Supplies come in all qualities, types, some good, some poor,
and some better.
What you are talking about is Per Cent Regulation.
( an old and historical feature, quality, or curse of power supplies )
To understand it, to some degree,
This is the Voltage under Full Load
Compared to
The Voltage under NO LOAD.
For some applications, this is very critical, for others it is not so critical.
One should know this when he embarks on the power supply journey. or
else ......... ! !
Most of us know about the older power supplies that consisted of only
a transformer,
rectifier ( many types ) capacitors, and maybe a resistor or two.
I never liked Half Wave, I always liked Full Wave rectifiers.
Later, with the event of new technology. transistors,
regulators, many integrated circuits, and on and on, Switching
Power Supplies, ( and other types ) began to make the scene.
Then, ........ along came UL listed power supplies. Some of the very
best, and high dollar power supplies we use today are in fact, UL
listed. These are used in Life Safety applications.
Not exactly a place to monkey around, of for a dumb old redneck to
build power supplies.
I have one power supply in my shop, I designed and built.
It is 12 VDC and 100 AMPS.
Large high quality heat sinks
Fans
Partitions to control the air flow ( the idea was for it not to Self
Destruct )
Next I have to build a device to load test it. Do that right or it
will not last thru ONE TEST.
Large Wire Wound Resistors that run RED HOT ! Simple math
says, 1200 Watts. Minimum
Place a steel plate on top, boil coffee, fry eggs, or bake bread with
some modification.
Another thing I must mention that is in order, is that............
High Speed Fuses are very different from ordinary fuses. They have
to be fast enough to protect the solid state devices. And they are not CHEAP.
For a few years, I was the field service rep for Chloride Systems,
Emergy Lite, Computer Power, and Hunt Electronics. Almost
forgot, Lighting Services, a large northern company I did work for in
MS, LA, AL, and GA. Nothing to it, ........ all in a days work.
A few times, I had to buy $ 200.00 worth of fuses before I did a service Call.
Of course many were 100 amp and 200 amp high speed fuses.
Every circuit, needs at least one fuse. Always, .............
480 / Three Phase Inverter systems, with about a TON of Batteries,
........ is in fact a power supply of sorts. Two large battery
cabinets, 4 feet tall, and 40 feet long.
Most of these have a "Low Battery Cut Off". It works so fast, you
will not know it functioned.
The Inverter will not work,......... and you scratch your head for a
while, one minute or two, maybe more. <grin>
And I do not claim to know all about power supplies, ....... just a
little, maybe.
Wayne
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