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Forum Index : Wanted : Generator head.
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I'm looking for a generator off a dead genset. Or even the whole genset. I have a old 1.5hp sidevalve engine I would like to put to use, and a 5hp sidevalve, and a 1000cc morris flathead. These are gathering dust, so it would be nice to couple them with a gen head and use as a backup power supply when the lights go out. I would prefer a genset with a stuffed motor, like those cheap 2 strokes. Leave a message here if you can help. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| KiwiJohn Guru  Joined: 01/12/2005 Location: New ZealandPosts: 691 |
Glenn I guess this might be a silly idea but here goes for what it is worth Considering that a synchronous AC motor goes to alternator mode when driven above it synchronous speed it may be possible for you to use a motor in this way. As I understand it the motor must be energised with AC at the appropriate frequency before speeding up to become a generator. So, how about a cheapo inverter (maybe only 50watts or so) connected to an AC induction motor. Of course the motor will likely not even start to turn but if powered by your engine and the revs increased to just above synchronous speed would you not have an AC alternator of much greater output than the inverter? I dont know if this is a silly idea or not but if the petrol engine was available here I think I would give it a go.
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Megawatt Man Senior Member  Joined: 03/05/2006 Location: AustraliaPosts: 119 |
I guess that KiwiJohn is referring to the use of induction motors as generators. The guts of this is that if you provide a rotating magnetic field to excite the machine and then drive it over synchronous speed, energy can come out. And its only a few % over speed. That is why some of the large machines can be changed over from direct drive to gearbox drive at critical wind speeds. So like with the very large induction wind machines, they are connected to the mains to provide the magnetisation and driven faster than synchronous speed, when they generate power. If the mains connection falls off, they stop generating and the brakes have to be applied to stop overspeeding. If you wanted to use an inverter to excite the machine I reckon you'd have to drive it up to synchronous speed before you connected the inverter, because when stationary, the machine would look like a short circuit. There may still be some surges when you connect it and the inverter would need to be capable of supplying almost purely inductive current, perhaps 25% of the nortmal full load current. Another way is to rely on residual magnetism causing a small voltage to be generated and connect the right sized capacitor to the machine. This would enable generation to proceed at almost any speed after the machine was driven fast enough to supply current to the capacitor. Of course the output frequency would be variable depending on driving speed. This technique is possible but I don't think it is used much. I think everything is too critical and the ratings of the bits have to be exact. http://www.redrok.com/cimtext.pdf is a site that talks about it. DONT TRY THIS AT HOME! Why did I say that? Because we are talking about 240 or 415 volt systems and the capacitors operate at voltages much higher than that. I can tell that most members of the backshed are good at low voltages but in general are not ready for the dangerous stuff. Megawatt Man |
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Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
Hiya Glenn, Eh mate I have a 5.8 Kva genset that has a siezed motor that came with the farm when we bought it. Now I'm not going to get rid of it as I have a few idea's with micro hydro for it. But if you happen to get the same I found out the way to get the alternator off the motor. The shaft is connected via a tapered screw thread and the only way to seperate them is fix the motor to a solid post and wrap a heap of hessian rope around the rotor so you don't damage any wiring. when you wrap the hessian leave a loop then wrap atleast 3 full wraps then use a crow bar after applying some heat to the shaft and pull like hell. This is the only way and the best way I reckon. By the way I was told this by an old bloke from Mt Barker who mentioned he knows a heap of people that have stuffed an alternator before he told them how to do it. Hope this helps your quest Glenn Cheers bryan  |
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| sangeff Newbie  Joined: 05/11/2005 Location: AustraliaPosts: 29 |
Hello Glenn, I have two honda generators in the shed and am going to make one good one out of them so I will have a spare set of coils. They'r only small camping size ones but your welcome to have the remaining one if you can get it up there. Give me a ring or email. Geoff |
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| domwild Guru Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Glenn, Just a suggestion: Doesn't Ecoinnovation use F&Ps as gensets in their sales catalogue? Have a look. No doubt you have thought about that too. They couple it on a board to an engine and flog it that way. dom Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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