alternator query

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Tue 20 Mar 2007 14:28
alternator query - milkyjoe
hi, on an alternater do the brushes pick up the a/c voltage output or do they supply voltage to the rotor ive heard conflicting stories ?
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Tue 20 Mar 2007 14:37
alternator query - pmh
Which bit from your previous thread / post did you not understand?



brush wires on alternator - Fiesta - Aprilia
Sat 17 Mar 07 15:28
The wires only carry the energising current to the rotor - not the output current!
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brush wires on alternator - Fiesta - milkyjoe
Sat 17 Mar 07 15:41
oic, so the output wire is connected to the 3 phase coils which are static then? that makes scence now,cheers
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brush wires on alternator - Fiesta - Aprilia
Sat 17 Mar 07 21:54
oic, so the output wire is connected to the 3 phase
coils which are static then? that makes scence now,cheers

>>

Indeed. Output is from the stator winding (3-phase) and rectified.
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pmh (was peter)


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Wed 21 Mar 2007 10:24
alternator query - milkyjoe
why do some basic alternator diagrams show an ohmeter across the brush contacts with an ocsilating reading to - then? there are many websites about with such animations , thats what im getting at ,you wimmy?
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Wed 21 Mar 2007 10:34
alternator query - Altea Ego
Think about it

Those silly little brush wires would be glowing like lightbulbs under 60+amps alternator output.

Short lived lightbulbs at that,
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TourVanMan TM < Ex RF >
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Wed 21 Mar 2007 11:45
alternator query - pmh
"an ohmeter across the brush contacts" is not the way to test a working alternator.

To put it simplisticly, the voltage measured across the brushes will be varying (dependent on alternator rpm (amongst other things)), as it is the way the output voltage is controlled by the the regulator. Not oscillating.
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pmh (was peter)


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Wed 21 Mar 2007 11:55
alternator query - Aprilia
The voltage regulator sends a duty cycle modulated square wave through the brushes. This modulates the average energising current through the rotor windings to give the desired output from the stator.
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Wed 21 Mar 2007 12:01
alternator query - Glaikit Wee Scunner {P}
A basic alternator will produce an oscillating output by its very nature.
The animated voltmeter on the output is intended to illustrate that on a classroom basis.

The practical car alternator has regulators to smooth out the voltage to charge the battery and power those brighter, non dazzling, headlamp bulbs.
--
I wasna fu but just had plenty.
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Wed 21 Mar 2007 12:16
alternator query - pmh
Aprilia -
I understand what you have posted but I am not sure most people will! That is why I tried adopted a KISS approach.


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pmh (was peter)


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