On Thu, 17 Feb 2005 20:37:46 GMT, Larry W4CSC wrote:

Gary Schafer wrote in
:

The fields in the air conditioner motors suddenly collapse when power
is removed. The collapsing fields will generate a high voltage spike
throughout your boats mains system. Any other equipment that is turned
on at that time will receive those high spikes of voltage. Everything
that is turned on is connected to the air conditioner motors. You can
guess what can happen with voltage spikes fed to some types of
equipment.

If you shut down the AC systems first you avoid any kick back voltage
spikes being fed to other equipment. The fields just collapse and no
voltage spikes go anywhere.


Wow! All this time I thought Tesla's multiphase AC power system had
collapsing fields 120 times per second, not when I unplugged the shore
power cable!....

Which one of the boater electrical expert books at Waste Marine did you get
all this bull**** from, anyways, Gary?

AC systems don't work like DC systems.....(c;


I know you slept through the basic AC theory class but the DC one too!
:)
As I am sure you missed the lab part too,
You can try for yourself. Take a little 12 volt ac motor or
transformer and connect its 12 volt winding to a 12 volt ac power
source. Hold on to each lead of the motor or transformer bare wires if
you dare. Touch them and remove them from the 12 volt ac source. I bet
you let go rather quickly. :)

Better yet hook your oscilloscope to the winding instead of your
fingers. Look closely as you disconnect the winding from the power
source. Turn the gain down on the scope so you can see the high
voltage spike before it goes off the screen.

You keep disconnecting the shore cable without turning things off
first and you wonder why your mov's are popping! Those things do wear
out you know, or do you?

Regards
Gary

"Gary Schafer" wrote in message
...
You can try for yourself. Take a little 12 volt ac motor or
transformer and connect its 12 volt winding to a 12 volt ac power
source. Hold on to each lead of the motor or transformer bare wires if
you dare. Touch them and remove them from the 12 volt ac source. I bet
you let go rather quickly. :)

Better yet hook your oscilloscope to the winding instead of your
fingers. Look closely as you disconnect the winding from the power
source. Turn the gain down on the scope so you can see the high
voltage spike before it goes off the screen.

That is why equipment is required to have a snubber network. This will
absorb most of the spike down to a safe level for other equipment on the
mains.

Meindert