Capt.Bill wrote:
Hey Larry, how up are you on 3 phase motors and controls?

A captain acquaintance of mine is having a bit of trouble with the
bow thruster system on a boat he has taken over in the Bahamas.
Perhaps you could be of help if you so choose.

http://www.yachtforums.com/forums/te...on/10616-roto-
phas
e-motor.html


This boat needs an AMERICAN shipyard with skilled technicians on that,
obviously, old system that looks kluged up to some new conversion.

My guess from what little is showing is it had a mechanical phase
converter to give the 3-phase motors on the thrusters old-fashioned 3-
phase motor speed control. Someone has changed that old system to a
newer solid state (see the new control box?) phase rotator to drive the
motors.

Of course, no documentation was ever done to DIAGRAM what was done to
it, as is just normal on 95% of the yachts at any dock. So, noone
knows, for sure, what was done and must start from scratch, read that
many BILLABLE man-hours that could have been saved by paying the
installer some manhours to document what was done long ago.

From the look of its older parts, it's replacement time, anyways, and
denial will simply extend the inevitable replacement time. New systems
with switching motor speed controllers and motors made to run from them
solve the problem.......er, ah....until that breaks, when the cycle
repeats.

Sorry, I can't help you from the pictures. Looks like a great
challenge, though. I fixed a motor-alternator set on an old yacht that
didn't work. It converted the 32VDC battery beasts to 115/230 2-phase
60 Hz long before today's highly efficient, powerful digital switching
AC inverters were invented. Besides the bad bearing a motor rewind shop
replaced for us, I had the original drawings and simply replaced the
rotten wiring and corrected 25 years of misconnections with the original
installation. It was actually quite quiet, considering it was running
at 1800 RPM to get 60 Hz all the time. By today's standards, the idle
32V at 2.8A wasn't very efficient, but this was a dual engine motoryacht
with FOUR 32v alternators running off two big v-belts, not a sailboat on
boat batteries, so it wasn't an issue. Keeping the beer cold in the big
GE refridgerator-side-by-side-freezer was. The look on his face when
those AC lights came on by pressing the red button at the helm was quite
PRICELESS....

The alternator could put out 6.5 KVA very smoothly.

He needs a good yard to replace it with a modern system......if he must
have it.