for what ever its worth....
I run 3 harris pelton turbines here that are rewound ford alt's for 48v.  I 
have removed the internal bridges and installed external ones...much better 
air flow for cooling.  I have replaces the standard brushes with the heavy 
duty round ones and now I only change them once a year.  Cant quite get two 
years out of them, so I just change them at the start of every season.  the 
comms have to be changed everyother year.

doug
----- Original Message ----- 
From: "Max Klohn" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Tuesday, October 18, 2005 4:53 AM
Subject: Re: [microhydro] auto alternator brush life--response to 
Oso'scomment


> Because you do not run your car 24 hours a day, 7 days a week, for
> months and years.
> Local experience with battery charger peltons is that brushes wear in
> about 3 - 4 months with the internal charge regulator (which cuts off
> induction current at full battery charge and causes the turbine to spin
> at nearly VJet) and 8 - 10 months with resistive field currrent control
> and constant turbine speed.
>
> Max
>
> Le lundi 17 octobre 2005 à 15:54 -0700, davis ron a écrit :
>>      That is the same thing I was thinking after
>> reading Oso's comment. I have only had alternator
>> failure a couple of times over 30 plus years of
>> driving. Wny would they wear out so much faster when
>> used with microhydro?
>>
>> --- Radu Babau <[EMAIL PROTECTED]> wrote:
>>
>> > Hello Oso,
>> >
>> >
>> > You are saying that:
>> >
>> > > Most alternators are rated at 6000 rpm, so it
>> > should produce the full
>> > > 70 amps. You do need to subtract the excitation
>> > current from that, so
>> > > I would not count on anything above 65 amps.
>> > >
>> > > Spinning it at that speed, the brushes are not
>> > going to last very
>> > > long, 6-8 weeks would be my guess. If you cut the
>> > speed to about 3000
>> > > rpm, the alternator should still produce 50-55
>> > amps and the brushes
>> > > will last a little longer, say 12-16 weeks.
>> >
>> > I am wondering about this 12-16 weeks brushes life
>> > time. Some of us have
>> > cars which we mostly ride in the city, 90% of their
>> > life time, on which the
>> > normal motor speed is something from 1000-3000
>> > rpm's. Usually there is
>> > something like 1.5 ratio between the alternator and
>> > motor shaft. Other
>> > people are mostly using their cars to run on
>> > highways, which means 2000-5000
>> > rpm motor speed. In both cases the life time of a
>> > alternator (including
>> > brushes) is at least 5 years, even more. It is that
>> > kind of equipment that
>> > you only change once during a normal car lifetime.
>> >
>> > Am I wrong ? Am I right ?
>> >
>> >
>> > Radu
>> >
>> >
>> >
>> >
>>
>>
>>
>>
>>
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