Slip ring failure

[Alan]

If your generator ( My one is the 1 K.W. ) still turns when the three phase cables are connected together suspect problems with the rotational three phase slip ring assembly. The carbon brush box is made of very soft fibre glass with no reinforcing. The brush furthest away from the mechanical mounting bracket by design has only got 0.5mm wall thickness on the brush holder. The copper cable on the brushes is very thin. It would probably be suitable for a 220 volt 200 watt machine where the current would be a lot less, but for a 1000 / 1500 watt machine at 48 volts ( lots of amps ) the losses are to great. The brush had over heated and the fibre glass brush box caught fire. Once the brush box initially starts to burn on the end where the wall thickness is only 0.5 mm thick,  play is introduced and the brush starts to arc and the whole assembly fails.
Repairs can be made by gluing plastic sides and ends to drastically increase the brush box wall thickness. The whole left where the brushes used to be can be built up to a solid using super epoxy and the brush positions are drilled then carefully filed out to the size of the new brushes. On reflection it would have been easier to start from new with a solid Teflon block. Obtaining brushes is not that straight forward any more. The old car Dynamo brushes were ideal because they were low voltage high current , found some in breakers yards.

Regards

Alan

[frotter]

You are not alone in this........ I luckily discovered the useless state of the brush mount block in my unit before letting the wind at it.

See - :

http://navitron.org.uk/forum/index.php?topic=1310.0

For chunky brushes you could go to a decent disability/mobility supplier and get brushes from electric scooters/wheelchairs. Some are really chunky. If you chat up the servicing dept they may let you have a rummage in their brushes bin......

 

[Alan]

Nice one Mr Frotter

Sorry Missed your previous posts. Grief factor could have been less here if I had seen it. As it was the blades trimmed branches of a tree where I could not stop it from rotating while it was lowered.

Here is one, well worth a mention for the bigger tail less machines.

http://navitron.org.uk/forum/index.php?topic=860.0 mention was made about the free play and back lash in the turbine position worm and wheel gear box. Also about the drive motor reduction gear box having sheered mountings and defective machining to the shaft key way.
 Normally in worm and wheel gear box’s both parts fit inside a precision made steel casting that allows for any play between the worm and wheel gear to be taken up by fitting shims to the worm bearing mounting blocks to remove any slight manufacturing discrepancy in the gear machining. This virtually removes any back lash in the gearing and drastically reduces wear.

On the turbine rotation device the worm would appear to be assembled complete with both bearings, then it is held in position while it is welded to the main rotation wheel / bearings with a 15 mm wide weld. Then the whole rotation assembly is also welded to the main generator case with another very substantial weld. The resulting weld temperature means that the worm to wheel mesh and resulting play is a total unknown quantity. The worm may not be any where near parallel to the wheel at all. If it was parallel and you have No way of knowing because the assembly is internally welded to the main casing. An oversize worm gear could be manufactured / machined to take up the majority of the excess play. As in my case it is no where near parallel so nothing what so ever can be done to rectify the defect.  The resulting failure of the worm teeth allows the generator to rotate freely then ripping out the supply cable with no means of shutting the machine down. You have no means of lowering the machine down because you cant stop it rotating. You just have to wait for the wind to drop and take a chance when lowering it. No point wearing a hard hat with three four metre long blades thrashing about.

 I am now fitting a substantial rotation gear box at ground level with a 100mm drive shaft fitted inside the tower.
The microprocessor controlled position controller has also been taken out of service, that used to drive at random causing the cable to twist and rip out. ( no electrical limit switches or torque limit switches are fitted. ?

 There is not much of the original turbine / design left. The challenge keeps me out of the pub though.

Can post pictures if required.

Regards

Alan