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60 hz 120vac out of a car alternator.

Discussion in 'General Electronics Discussion' started by BigMcb, Apr 13, 2010.

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  1. BigMcb

    BigMcb

    2
    0
    Apr 13, 2010
    Hey guys, I know this has been brought up before but I didn't find a good response. Lets say, just focusing on the three phase output of the alternator, we spin the rotor up to a speed that will produce 60hz on the output. Then we adjust the rotor field (using an outside DC source) to get 120vac off the stator leads (just use two of them ignore the third). Wouldn't that run a 120vac load? Or am I missing something?
     
  2. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    Yes, you are. The alternator is designed to run balanced loads on the 3 phases. When you run it unbalanced like this, what happens to the two unused phases? What will the voltage be on those and where will it arc to? You will likely have to add dummy loads, which will heat up and cause other problems.

    Will you have enough control on the field winding to the drive the voltage up to 110V? If so, how much power will you be able to get out of the alternator as it operates well past the design point?

    All this assumes that you have already removed the diodes.

    Do you have an engine controller that will maintain a constant speed as the load changes? If you are just going to fix the engine throttle position (the fuel flow) the engine speed will change due to the load and your frequency will change.

    Can this be done? Yes, it is done all the time with standby generators. Can it be done by modifying an automotive alternator. Like not. Even if you can cobble something together that kind of works under certain conditions, the tasks involved are a lot more involved than your simplistic view.

    ---55p
     
  3. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    The 4 year old thread in the newsgroup mirror that you replied to yesterday brings up most of the valid issues even if it doesn't reach a conclusion.

    The most important issue here is that if you need a 60Hz output the alternator has to spin so slowly that you won't be able to "field" it sufficiently to make 120V.
    And if you rewound it for higher voltage then you wouldn't get much power from it.

    Then there are all the other aspects that 55p mentions, like voltage & frequency stability. If it had been easy you can bet some manufacturer would have made it.

    What, apart from 120V (+/-?), are you looking to get from the alternator? What are you intending to run off this? Is the frequency actually important for the use?
     
  4. djrobotfreak

    djrobotfreak

    7
    0
    Apr 14, 2010
    Yes, I am pretty sure that would work.
     
  5. 55pilot

    55pilot

    434
    3
    Feb 23, 2010
    And you basis for that claim is?

    Remember, wishing that it were so, does not actually make things work.

    ---55p
     
  6. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    That is the way an A$$H0LE makes a first post to get linking privileges.
    You are SO close to being banned for doing just that.
     
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