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Hydraulic motor-AC generator coupling

  1. Feb 4, 2017 #1
    Hi there. I have an idea which is interesting. Let's suppose, we have AC generator which has capability of 100 KW and 100 RPM. And we have hydraulic motor which produces 500 RPM and 2400 Nm torque. Additionally, I attach 5:1 gearbox for reducing 500 RPM to 100 RPM for Ac generator. Please, share your thoughts, is it possible to produce high efficiency and electric energy with this combination?
     
  2. jcsd
  3. Feb 4, 2017 #2

    NTW

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    Die Energie der Welt ist konstant (Clausius)
     
  4. Feb 4, 2017 #3

    russ_watters

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    Staff: Mentor

    Welcome to PF!

    Depends -- what is making the hydraulic motor spin? And what do you consider "high efficiency"?
     
  5. Feb 4, 2017 #4

    mfb

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    2016 Award

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    The hydraulic motor will need a power of at least 125 kW. Where is the point?
     
    Last edited: Feb 4, 2017
  6. Feb 4, 2017 #5

    Dale

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    125kW input for 100 kW output is not generally considered high efficiency. In practice it would be even less than that.
     
  7. Feb 4, 2017 #6
    The hydraulic motor is spun by hydraulic pump. And the hydraulic pump is powered by electric motor.
     
  8. Feb 4, 2017 #7
    Here is the clarification of what I want to get. I want to use hydraulic mechanism to get electric power. Hydraulic mechanism can be cylinder or hydraulic motor.
     
  9. Feb 4, 2017 #8
    Hydraulic motors have 10 times more power density than electric motors have. I want to get mechanical advantages from hydraulic motor torque to generate electric power. That's all.
     
  10. Feb 4, 2017 #9

    mfb

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    You cannot generate electric power from nowhere. You need a power source: A generator driven by hot gas, water, wind, ..., light shining on solar cells, or something else.

    Converting energy from one type to another is always associated with losses. Electricity -> mechanical motion -> electricity means you get strictly less electricity out than you get in. It does not matter which type of motor and conversion you use.
     
  11. Feb 4, 2017 #10

    Dale

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    Power density is not relevant to the question of efficiency. For efficiency all that is considered is the input power and the output power. It doesn't matter how dense the power is, just how much goes in and how much comes out.

    Based on your numbers above at least 125 kW hydraulic power goes in and at most 100 kW of electric power comes out. That is not a very high efficiency, but might be acceptable in some scenarios (e.g. If the hydraulic power were very inexpensive so you could sell the smaller amount of electrical power for more)

    Sure. That is what a hydroelectric power plant does. As @mfb and I have said, the efficiency of such a conversion is strictly less than 1.
     
    Last edited: Feb 4, 2017
  12. Feb 4, 2017 #11
    Guys, here is the point. A typical hydraulic press consumes 5-7 KW electricity to obtain 50 ton (500 kilo newton) capacity for pushing/pulling. Its hydraulic rod travel is 2in/sec. Let's suppose, if I use that rod in a reciprocating pump, I will get a very high torque, especially if the AC PM generator is has a very low RPM (50 RPM is available in the market!). I want to use hydraulic press mechanism in reciprocating pump and couple them to 100 KW PM generator. That's it.
     
  13. Feb 4, 2017 #12

    Dale

    Staff: Mentor

    Perperual motion machines do not work and are not discussed on PF. Thread closed
     
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