TO: ALL CONCERNED
FROM: S/V BANDERSNATCH
SUBJ: KISS Wind Generator Repair
Symptoms
No output from starboard wind generator. Low output from port wind
generator along with noisy, vibrating, operation.
Investigation
I measured the wild ac output from the starboard generator and found no
voltage on all three phases. I secured the unit and found no continuity on
all three phases.
I measured the wild ac output from port generator and found voltage on only
one phase. I secured the unit and found continuity on only that phase.
Disassembly
I removed the turbine assembly from starboard unit and took down unit and
mast. I removed the four long securing screws from front housing. I cut
the rubber caulking between main housing and cap housing and carefully
pried off the cap housing with a screwdriver and other prying tools
exposing the turbine end of the rotor and the stator. I removed the shaft
seal and rubber bearing shim from cap housing, cleaned them, then lightly
greased and replaced them in the cap housing after cleaning the cap housing
and set it all aside.
The rotor has powerful magnets, a primary reason this unit has the high
output it does, and they are very reluctant to leave the stator. Don't
even try. Rotor and stator must be removed and handled as a unit. This
requires considerable effort to persuade the rear bearing to leave its
home. I used a inertia puller consisting of a sliding weight on a shaft
which is connected to a large gear puller in place of the gear puller's
usual pulling screw. I removed the turbine blades from the hub and
replaced the hub onto the rotor shaft. With the unit lying on a folded
blanket and the tail secured by a 1/2' rope to the vessel, I held the three
gear puller claws onto the turbine hub while Jan operated the inertia
puller weight. After several increasingly vigorous strokes of the sliding
weight the rotor and stator came out from the housing thus exposing the
electrical connections which were all on the rear of the stator.
I cut all the shrink wrap and removed it from all of the connections. Some
of the shrink wrap had adhesive on the inside so care must be take not to
damage anything, especially the delicate stator wire insulation, while
removing it.
Inspection
The stator consists of a laminated iron piece with holes and slots forming
poles and many windings of varnished solid copper wire through the holes.
The wire is arranged in three separate coils, each passing through every
third hole, thus creating the three phase ac output as the magnetic fields
of the rotor sweep past the poles. The ends of these coils are brought out
to the rear of the stator, the insulation removed from the ends and the
wires twisted together in a daisy-chain fashion to connect the three stator
coils in series. Quarter inch female quick-connect terminals are crimped
and soldered to each twisted pigtail. The three feed wires that carry the
generator's output to the boat are also fitted with crimped and soldered
quarter inch female quick connect terminals.
One feed wire is connected to one stator terminal using a male/male quarter
inch quick-connect bridge and then covered with a piece of shrink tubing.
The other two feed wires are connected to the other two stator terminals
via thermal switches provided to protect the unit from high temperatures at
wind speeds above approximately 25 knots. These thermal switches are about
a half inch in diameter, three eights of an inch thick, with two male
quarter-inch quick connect terminals on one end. Each thermoswitch is
protected by a generous length of thick-walled shrink wrap.
On both terminals of the solid copper stator wire connected to the two
thermoswitches the stator wires were broken where it entered the terminal.
It appeared obvious to me that the normal vibration of the unit, coupled to
the fact that the thermoswitches, along with the extra weight of the
heavy-wall shrink wrap, were simply left hanging in space and not secured
to the stator, resulted in sufficient movement to produce stress hardening
of the solid copper wires resulting in fracture.
The Fix
I removed the two thermoswitches and the male/male bridge. I clipped off
all the remaining quick connect wire terminals. I removed about 3/8" of
insulation from the three feed wires and tinned them. I carefully scraped
the varnish insulation off the six stator wires for about 3/8" and twisted
them together keeping the three phases in series, then tinned them. I
tinned the insides of the four quarter inch male connectors on the
thermoswitches.
To do the soldering I used a 115 Watt, old fashioned soldering iron (which
I found in an antique shop years ago). You could do this with a propane
torch with soldering attachment but be sure to turn the torch off before
soldering to prevent the flame from damaging anything. Using a large
soldering iron allows one to get the solder joint up to melting temperature
quickly before the heat has a chance to spread out. I then cool the joint
to freeze it by blowing on it followed by a wet q-tip to further lower the
temperature to prevent heat spreading.
I soldered everything together so it was electrically the same as the
original arrangement. While doing this I positioned the thermoswitches
parallel with, and close to, the stator windings. After soldering I
installed heat shrink tubing over the connections and thermoswitches.
After that I secured everything to the stator using some poly whipping line
I had in my boson's bag. Real motor twine would probably be better. I
finished the lashings with double pass square knots and a daub of
fingernail polish on each to lock the knot.
The port unit was treated exactly the same as the starboard unit. However,
I did not find any broken wires. Since all the wires were securely
soldered to their terminals I had to assume that there was a bad connection
on the metal surfaces inside one of the quarter inch quick connects.
Soldering everything together eliminated the problem and the unit now works
properly.
The starboard unit showed signs of water intrusion but the port unit did
not. I don't know why.
Re assembly
I put a light coat of grease on the bearings and rotor shafts to help keep
corrosion at bay. Everything went back together easily on the starboard
unit but the port unit was stubborn requiring more forceful persuasion.
Eventually I prevailed but one of the four long securing screws lost its
mating threads (threads simply cut into the plastic) in the housing.
Sealant between the two housing pieces needs to be replaced just before
final closure.
Operation
After reinstallation both units operated normally. The ac output on all
three phases of each unit were approximately equal and the DC outputs from
the rectifiers were also equal and normal.
Conclusions
The broken wire failure was built in at the factory by not tying down the
thermoswitches but allowing them to move, eventually resulting in fracture
of the stator wires. The failure of the portside unit could have been
prevented by soldering every connection inside the unit and not relying on
the quick connect fittings.
Stainless threaded inserts in the main housing to prevent stripping out the
weak plastic threads there would be a welcome touch.
Owners of these machines may opt to correct these shortcomings at their
convenience rather than wait until failure. Simply tying down the
thermoswitches should prevent the wire fractures. Prevention of the
presumed failure of the quick connect I had in my portside unit will
require more work. Perhaps removing the shrink wrap, disconnecting all the
quick connects, application of Kopper Kote (like Never Seeze for electrical
connections) to the mating surfaces, reconnection, reinstallation of shrink
wrap and then tying down will do the trick.
As they say: Do it right or do it over...
Norm
S/V Bandersnatch
Lying Annapolis MD
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