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Homework Help: Generator Project

  1. Nov 29, 2014 #1
    I'm a graduating student of Electrical Engineering Technology (3 years) and so one of our graduating subject is thesis. We decided to make a generator that can supply the house and supply itself by giving some of the power to back to the motor which rotates it. We also included batteries and PLC.

    It works like this, first the battery will power the motor, the motor will spin the generator. Some of the power will go back to the motor and the battery. Once the power from the generator goes back to the motor, using PLC, the battery will now stop supplying the motor and recharge, it will only supply back the motor when needed, using PLC. We still haven't made design for the PLC.

    The problem statement, all variables and given/known data


    The problem is how much power will be delivered to the load and if this design is actually possible. I have this feeling that all of the power will be consumed by the transformer. To find out how much power will go to the load, I need to know how much current will go to the transformer.

    The motor will need around 85 amperes in order to operate. So that means the output current of the transformer should be around 100 amperes since some of the current will go to the battery to charge it.

    The ideal transformer formula is power in equals power out.
    So the output power of the transformer is (24V x 100A) = 2400W
    The input power is (230V x I) = 230I
    230I = 2400
    I = 10 A

    That means the transformer needs an input current of 10A, since it is not an ideal transformer the value is higher than 10A.

    The attempt at a solution

    My classmates said that we will put super capacitor in around the battery. With the help of super capacitor, the charge rate of the battery will increase and its discharge rate will decrease. But I feel even that won't help. They're just mostly laughing while I'm explaining this problem to them. They keep on saying it will work and that I don't need to worry. I'm thinking of leaving the group and join other groups instead.

    Another thing is the rate of charge of battery. How do I calculate the number of hours it will take to charge the battery. I've come across the formula h = (Ah of battery/A of charger) where h is the number of hours it will take to charge the battery. Does this mean that I can fully recharge a battery very very fast if it can take a large amount of current?
  2. jcsd
  3. Nov 29, 2014 #2


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    Staff: Mentor

    Hi jovel.happy. Welcome to the famous Physics Forums!

    In your 3 years of study, it's surprising that none of your subjects dealt with this fantastic idea your group is preparing to demonstrate. Surely someone else must have thought of it before now? It would be so revolutionary if it could be made to work.

    Has anyone in your group voiced misgivings about it, or do you anticipate any significant problems?
  4. Nov 29, 2014 #3


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    Staff: Mentor

    Welcome to the PF.

    What you are describing is a "Perpetual Motion Machine" (PMM) or Over-Unity Device. Each of these is a forbidden topic here at the PF. Please follow the links in the quote below from the PF Forbidden Topics List to learn more about why PMMs cannot work.

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