[clug] Exercise and pay the bills!

Neil Pickford neilp at goldweb.com.au
Mon Feb 9 21:50:04 GMT 2009

May I suggest a Truck Alternator 24V.
You can also get alternator stators rewound.

Uncontrolled (without a properly working regulator) alternators can 
produce over a hundred volts so I would suggest a truck alternator with 
a regulator modified to control output at 48-52 volts.

A vehicle alternator is a 3 phase alternating current machine with 3 
windings on the stator each with a set of 6 big diodes to rectify the 
output to a common DC output Bus.  By using a Truck alternator you will 
get higher voltage capability diodes which would be more suitable for 
the task. As stated earlier any alternator would easily absorb the 
energy that a human could produce.

The regulator supplies current to the rotor electromagnet via slip 
rings.  The stronger the current in the rotor the higher the Electro 
Motive Force (EMF = Voltage) induced in the stator windings. This is why 
full voltage on the rotor (due to a regulator fault) can produce 
hundreds of volts.  I had a mate who had the problem in his car (battery 
lead fell off causing the regulator to loose it's reference [poor 
design]) and all the electrical components fried and caught fire as he 
was driving along.

Generally the regulator gets its operating voltage from a central star 
point in the stator windings which is approximately 1/3 of the output 
voltage but you do need a voltage source (battery to get things going in 
a nice stable way).

Neil Pickford.

Sam Couter wrote:
> Robert Edwards <bob at cs.anu.edu.au> wrote:
>> A (smallish) car alternator (ie. 13.8V) and a 12V-48V inverter might be
>> the best bet to get 48V into your power feed-in.
> This discussion drifted in all sorts of amusing and off-topic
> directions, but I just wanted to come back to this bit.
> A car alternator usually produces close to 15 volts if the regulator is
> still working correctly. A lead-acid battery is nominally 12V but really
> produces 13.8 and the alternator needs to charge that, not just meet it.
> So it's a little higher. I don't know how easy it would be to just
> replace the regulator with your own to make the alternator output 48V
> instead of messing with a 12V-48V converter before the 48V-240V
> inverter.
> Also, the smallest car alternator you're likely to find can probably
> handle at least 300W or so output, which is more than you'll be producing
> on an exercise cycle unless you're a metabolic freak like Lance Armstrong.
> So I don't think you need to worry about getting one that's big enough,
> any will do.

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