Exciting my altenator? One for the sparkies!
Submitted: Tuesday, Mar 28, 2006 at 21:01
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Stuart
Hi all again, I can't remember how to make an altenator self excite so I can use it for my generator. Can someone help??
For those of you that helped me last night with with my generator/ compressor thank you. I finished the altenator pullies today and gave it a
test run and it works a treat. I had only 12.27 volts in the main battery of my Cruiser (time for a new one) and even with the headlights on the little 4 stroke was able to get the altenator to pump 13.8- 14 volts into the battery at just above it's idle. When I turned the lights off the volts jumped to 14.3 volts exactly. Looks like my gearing up the altenator about 5 to 1 was OK. You could hear the load come onto the engine but it made little difference to it and the govenor works
well to keep the revs even.
Tomorrow i will start on the compressor part of the job.
Cheers for now!!
Reply By: Eric Experience. - Tuesday, Mar 28, 2006 at 21:52
Tuesday, Mar 28, 2006 at 21:52
Stuart.
Alternators do have a little residual magnetism but not enough to produce the 2 volts or so required to get an electronic regulator started, one solution is to revert to a mechanical regulator. The better solution is to use a generator, a generator is about 50% eficient and will have enought residual magnetism to start, an alternator is about 25% efficient so it rquires twice the power to provide the same charge. Eric.
AnswerID:
163547
Reply By: Richard Kovac - Tuesday, Mar 28, 2006 at 23:51
Tuesday, Mar 28, 2006 at 23:51
No but!
out of one of my books
"Illustration shows the self-excited alternator which has three additional diodes on the rectifier pack to pass a portion of the alternator output current to the field winding. When the ignition switch is turned ON, the field winding is connected to the battery via the NO-CHARGE warning lamp. The small current flowing through the field winding produces a magnetic field which is sufficient to begin the build-up of the alternator output voltage through the auxiliary diodes. As the voltage builds up, the same potential will be applied to either side of
the pilot lamp and extinguishes it"
Richard
ps add the light and kick it in the guts
AnswerID:
163560
Reply By: kesh - Wednesday, Mar 29, 2006 at 07:51
Wednesday, Mar 29, 2006 at 07:51
Assuming your alternator is a Bosch with inbuilt voltage regulator simply having a wire from the output terminal (+) on the alt, through a switch to the field or D terminal will start the alternator. The alternator must be connected to the battery and do not disconnect whilst running or goodbye diodes.
kesh
AnswerID:
163579
Follow Up By: Member - Mike DID - Wednesday, Mar 29, 2006 at 16:57
Wednesday, Mar 29, 2006 at 16:57
"The alternator must be connected to the battery and do not disconnect whilst running or goodbye diodes. "
This is worth repeating if you have a temporary setup - make sure the connection scannot come apart. You can't just connect a load to the Alternator output without having special surge protection if the load is less than the Alternator capacity.
Keep in mind an Alternator does not put out DC - it puts out chopped DC (rectified AC) which could damage some loads.
"The alternator must be connected to the battery and do not disconnect whilst running or goodbye diodes. "
Mike
FollowupID:
418437
Reply By: Stuart - Wednesday, Mar 29, 2006 at 11:26
Wednesday, Mar 29, 2006 at 11:26
Thank you guys. I don't want to use a generator as they are a fair bit heavier and harder to come by these days. I think I will go with the old altenator idea as I can also adjust the regulator to put out a bit more zap and I have a couple of those to.
Thanks again this
forum is excellent.
AnswerID:
163611
Follow Up By: Member - Collyn R (WA) - Thursday, Mar 30, 2006 at 09:19
Thursday, Mar 30, 2006 at 09:19
Stuart
Alternators are designed to give about 70% of their output at 4000-5000 (alternator) rpm. Safe to run most of them as high as 15,000 - but there's not much increase beyond 8000.
If you need more specific data contact me directly.
Collyn Rivers
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