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techtalk:ih:elec02a [2018/12/16 19:30] hippysmack [Bench Testing a Generator] |
techtalk:ih:elec02a [2018/12/16 23:31] hippysmack [Brush assembly] |
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(these can be hard to diagnose, and probably need testing on the bike so the genny can be driven at varying revs). \\ | (these can be hard to diagnose, and probably need testing on the bike so the genny can be driven at varying revs). \\ | ||
- | * Generators are fairly simple, they consist of; | + | |
+ | {{ :techtalk:ih:elec:generator_drawing_1_by_sifty.jpg?direct&500|}} | ||
+ | * Generators are fairly simple, they consist of; ((photo by sifty of the XLFORUM ((http://xlforum.net/forums/showthread.php?t=1592463&page=42)) | ||
* Field windings are designated "F" (attached to the case). | * Field windings are designated "F" (attached to the case). | ||
* Armature windings are designated as "A" (wound around the rotating shaft). | * Armature windings are designated as "A" (wound around the rotating shaft). | ||
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* There are no short circuits. | * There are no short circuits. | ||
* And the commutator, brushes and bearings are clean and in good order. | * And the commutator, brushes and bearings are clean and in good order. | ||
- | + | \\ | |
- | {{:techtalk:ih:elec:generator_drawing_1_by_sifty.jpg?direct&400|}} ((photo by sifty of the XLFORUM ((http://xlforum.net/forums/showthread.php?t=1592463&page=42)) | + | \\ |
+ | |||
====== Brush assembly ====== | ====== Brush assembly ====== | ||
- | The brush plate is easily removable, and inspection/ cleanup should be straight forward. \\ | + | {{ :techtalk:ih:elec:generator_pic_by_sifty.jpg?direct&400|}} |
+ | The brush plate is easily removable, and inspection/ cleanup should be straight forward. ((photo by sifty of the XLFORUM ((http://xlforum.net/forums/showthread.php?t=1592463&page=42)) \\ | ||
Care must be taken when installing the brush plate. \\ | Care must be taken when installing the brush plate. \\ | ||
Make sure that the brush- armature connecting wire is not pinched (can short circuit to the frame). \\ | Make sure that the brush- armature connecting wire is not pinched (can short circuit to the frame). \\ | ||
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Ensure the connecting wires are tightened in a position to allow full movement. \\ | Ensure the connecting wires are tightened in a position to allow full movement. \\ | ||
And make sure the bare end of the armature brush wire does not contact the case or end cap on assembly. | And make sure the bare end of the armature brush wire does not contact the case or end cap on assembly. | ||
+ | ====== Terminal insulation ====== | ||
+ | |||
+ | The terminals must be insulated between where they go through the case and connect to the windings. \\ | ||
+ | There will be some sort of fiber or plastic bushing around them at this point. \\ | ||
+ | These can crack or lose their insulating properties through a build up of dust/oil/ grime. \\ | ||
+ | A good cleaning may restore things. | ||
+ | But you can make new plastic bushes to replace the decades old fibre/plastic ones that are beyond salvage. \\ | ||
+ | The winding insulation test below will indicate the status of this insulation. | ||
+ | |||
+ | ====== Armature ====== | ||
+ | |||
+ | Testing on the Ohms scale between each commutator segment and the exposed iron core will indicate any short circuits to ground. \\ | ||
+ | Each segment should show very high resistance to ground (ideally in the Mega-ohms range). \\ | ||
+ | You can also test between adjacent segments for continuity (this reading should be very low) in the 0.1 ohm sort of range. \\ | ||
+ | Make sure you do not damage the soft copper of the commutator with the pointy test leads when carrying out these tests. \\ | ||
+ | The the armature is where most problems should occur and these tests are very rudimentary. \\ | ||
+ | But rule out obvious issues to begin with. | ||
+ | |||
+ | ====== Simple Generator tests ====== | ||
+ | With the generator cleaned, assembled and on the bench, some simple test with the multimeter in the Ohms scale can tell you a lot about its electrical health. \\ | ||
+ | The figures noted here were the results from 2 generators (different models). \\ | ||
+ | They should be reasonably typical the standard 12V Harley generator. | ||
+ | |||
+ | {{ :techtalk:ih:elec:generator_drawing_2_by_sifty.jpg?direct&400|}} | ||
+ | Field winding resistance: \\ | ||
+ | Placing the leads across the A and F terminals will give you the effective resistance of the field windings (2 windings in series). \\ | ||
+ | The armature circuit is not included as in a healthy generator there is no return path via ground to the meter. \\ | ||
+ | This should be around the 5.8 ohm mark, a higher figure indicates a possible open circuit, and a lower figure may mean a winding is shorting out somewhere. | ||
+ | |||
+ | Armature resistance: \\ | ||
+ | Placing one lead on a good, clean ground point on the case (shiny metal) and the other on the A terminal, will follow the path through the armature to ground. \\ | ||
+ | This should be very low, typically less than 0.6 ohms but can vary as it depends on the brush/commutator condition. | ||
+ | |||
+ | Total resistance: \\ | ||
+ | Placing the leads on a good ground point and the F terminal effectively measures the field plus armature circuits in series (from the F terminal, through the field windings, then through the armature to ground). \\ | ||
+ | As a quick check, this result should be very close to the values of the previous tests added together. | ||
+ | |||
+ | \\ | ||
+ | |||
+ | {{ :techtalk:ih:elec:generator_drawing_3_by_sifty.jpg?direct&400|}} | ||
+ | With the brushes out there are a couple of further tests available: \\ | ||
+ | Winding insulation: \\ | ||
+ | Placing one lead on a clean ground point of the casing, and the other on either terminal (do both) should give a very high reading (ideally in the Mega-ohms range). \\ | ||
+ | This indicates the windings are not shorting to ground anywhere. | ||
+ | |||
+ | Winding current: \\ | ||
+ | Connecting the battery through the multimeter in the Amps scale should result in a DC current of around 2 amps. \\ | ||
+ | Ohms law states V = IR, so with 12V and a resistance of around 6 ohms I = V/R which gives the 2 amps (will vary in practice as your winding resistance and battery voltage will differ). \\ | ||
- | {{:techtalk:ih:elec:generator_pic_by_sifty.jpg?direct&400|}} ((photo by sifty of the XLFORUM ((http://xlforum.net/forums/showthread.php?t=1592463&page=42)) | + | Motor test: \\ |
+ | This is probably the best indication, as a generator that will motor with voltage applied indicates all is well with the commutator / brush assembly. \\ | ||
+ | Jumper leads from a good battery were used and a short piece of wire (applied +12V to the A terminal, and -12V to the case and F terminal simultaneously). \\ | ||
+ | The generator was immobilized in a bench vise (between blocks of wood) for this test. \\ | ||
+ | It should rotate quietly and smoothly, with no sparks apart from when you make the connection. \\ | ||
+ | If it motors nicely there should be no reason the unit will not generate when spun. \\ | ||
+ | There are other tests available with the generator on the bike. \\ | ||
+ | (open field voltage, closed field voltage, current tests, all detailed in the manuals) \\ | ||
+ | But if the above tests go OK, \\ | ||
+ | A simple voltage test with the bike running should (hopefully) show around 15V at the A terminal to ground above idle speed, and you are away and riding... \\ | ||
\\ | \\ |