On Dec 4, 5:31 pm, N9NEO wrote:
On Dec 3, 7:58 am, wrote:



You don't know the half of it.

If it is electronic or even electrical in nature I tend to get
dragooned.

If I wrote about most of the oddities you guys would have me committed
in a rest home.

Up until injured myself on the job, I did a lot of "free lance"
trouble shooting.
Paid very well even if it was almost always weird beyond belief.

A friend is rebuilding a Triumph "Spitfire". While Lucas electric
certainly didn't
invent the short circuit, shoddy design and construction and evil in
general,
they clearly raised it Olympian levels.

Do you know why the Brits drink warm bear?

Lucas made their fridges.

I had never seen a stock car that used two 6 volt batteries in series
to get 12V.
And positive ground...I had managed to avoid dealing with that for 56
years.

My friend is adding a modern alternator and switching to 12V negative
ground.

Would anyone hazard a guess why the starter motor will not have to be
changed?

The wiper and blower motors can have the power leads reversed to get
proper
rotation. But the starter is bonded nicely to the engine frame.

My part of this was trying to explain why he didn't have to replace
the starter
and to design a better wiring loom with enough fuses to offer some
real protection
in the event of a nasty short. Given the switches are stock
Lucas....it stuck me
as a very good idea to add some more fuses.

The radio had died a lifetime ago, kind of sad because it had LW on
it.

So yea, I do post the strangest stuff......I am blessed to live such
an interesting life,

Terry

Hi Terry and others.

To answer your question (if it hasn't already been answered) - If you
reverse the polarity to the charging motor the field will be reversed
but the armature current will also be reversed. In the end the torque
is in the same direction so that the motor spins in the same
direction. I think that most starter motors are probably wound in a
series manner so that the armature current and flux producing current
are the same.

Bearing currents and the resulting failures have been known for quite
some time. That's what happens when you put large dv/dt on a motor.
Bearing failures were well researched at UW-Madison while I was there
in 90s. I suspect a lot of grant money. The motor manufacturers go
out of their way to build motors that are good to go with drives.
Better bearings, and insulation and so forth. I worked in drive
business since 1979 so I've seen the motors get better and better.

I'm going to have to disagree with the notion that high efficiency
motors are lighter than standard efficiency motors. The way to reduce
losses is to increase the copper and steel. Before high efficiency
motors came along people would oversize a motor by a frame size in
order to increase effiency. Smaller motors, fractional - 1hp are
especially inefficient, but cost is usually the driving force rather
than losses.

Now I design power supplies for military radios. I like getting paid
for playing with radios :-)

regards,
NEO

Yep, it is called a series motor. My first real job was at a low end
stereo store that
sold and installed 8-tracks. A Chevy of some sort had managed to
discharge and
recharge the battery back words. Negative became positive. His wipers
were also
series, and since it was summer he hadn't noticed his blower ran
backwards.

Another tech installed several 8-tracks only to have them "blow up",
let out the magic
smoke. I decided to use a VOM and check the battery. I hadn't had any
experience
with automotive electrical systems as I rode a manual start
motorcycle. This was a
part time gig while I went to tech school, while still in high school,
well before I decided
to become a real EE.

The owner couldn't believe a car would run with the electrical system
backwards.
The next day at school I went to the auto mechanic section and asked
to borrow
a starter and a battery. Once I verified the polarity didn't matter, I
asked if they
had a a starter for me to tear apart. Even then they didn't rebuild
them. I was
surprised at how there was no magnet, just a few turns of very heavy
copper
wire and brushes the size of my thumb. I went back to class and looked
up motors.
We had glossed over them with no real detail. I had diagramed the
starter and
once I found a series wound motor I understood.

The mechanic teacher showed me a neat trick to tell if the coil was
wired correct.
Apparently back then there were a few 4 terminal ignition coils and
while the engine
will work with a "backwards" spark, it doesn't run well. You pull a
plug lead and hold
wooden pencil lead, I put a pieced of drafting lead in a plastic
straw, I am not getting
shocked any time I can avoid it. You put the lead in the arc path. A
thick arc from the
lead to ground means the coil is OK, a thick arc to the plug lead
means it is wired
in reverse.

As too higher efficiency being heavier or lighter, all of the units
they have replaced here
at at my previous place of employement, a state university under
mandatory energy
efficiency increase requirements, the same rated motor was about 2/3
the weight.
I "inherited" several nice, nearly new motors that had to be replaced
under the mandate.
I do not deal with heavy duty commercial/industrial electronics, so I
based my opinions
on my personal experience and what my retired electrician friend
said.

I suspect that while bearing currents have been known for a long time,
the recent
addition of all these variable speed controllers to older 3 phase
motors has created
problems that didn't exist before. I received some interesting Emails
detailing other
methods of dealing with the problem then ceramic bearings. Several
companies make
conductive fiber "static" brushes warrantied to last 10 years of 7/24
operation on 3600RPM
motors. I passed it on to our maintenance guys because the ceramic
bearings are very
pricey and will not last as long as the steel ones. The brushes were
cheap, less then
$100 per motor. I also sent the links to my friend with the Panasonic
variable speed
heat pump. I have some doubts if they will work because I suspect the
compressor
motor is sealed. Our big air handler has the shaft available at each
end. The HVAC
company is saying that my friend is nuts and there is nothing wrong
with the unit.
Based on what we experienced at work, I bet his compressor dies before
Christmas.

Terry