Cars, cars and electric cars

Discussion in 'Just Talk' started by joinerjohn1, Jul 26, 2017.


  1. No, just watching the hole getting bigger I thought Id give a suggestion.

    Not been on the naughty step. Its just after a while of knocking my head against the wall, metaphorically speaking, I had to stop the pain and gave up for a while.

    I still dont even know why I got put on the naughty step. I may say things people dont like but I never get personal. So even the innocent get unfairly treated :rolleyes:
     
  2. Mr. Handyandy

    Mr. Handyandy Screwfix Select



    It's one or the other. Are you a politician?
     
    longboat likes this.
  3. chippie244

    chippie244 Super Member

    What an idiot :p:p
    You will be telling us how to use a bench grinder next :):)
     
  4. fillyboy

    fillyboy Screwfix Select


    Maybe you'll go down in history Jack, 'The Birmingham 6', The Guildford 4, 'The Screwfix 1'.;)
     
  5. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    "Reluctance - the ability of a magnetic circuit to block magnetic flux - is responsible on for the sensation of "cogging" i.e. torque ripple in various kinds of electric motors. It is not a dissipative phenomenon and does not have anything to do with the changing average torque demand of an alternator with variation in the power demand of the circuit connected to the terminals.

    The average torque required to drive a generator or alternator at a particular speed is related only to parasitic losses (bearings, etc) in the device and the electrical load imposed by whatever is on the output terminals. Physically what's going on is that a greater load (one with lower resistance) allows more current to flow at a given voltage: the greater current creates a larger magnetic field opposing the motion of the rotor.

    Reluctance, in particular the variable reluctance of the motor across its range of travel, is only responsible for small variations in torque and imposes zero average torque on the motor. "


    As far as I'm concerned, the alternator runs at maximum all the time(when engine speed is sufficient) but the regulator only lets through what is needed. So when more is needed the alternator need not produce more, it already is.
     
  6. chippie244

    chippie244 Super Member

    You stick to what you believe wether it's correct or not, why change the habits of a life time :p:p:p
     
  7. Or, to gently emphasise the relevant point;

    "Reluctance - the ability of a magnetic circuit to block magnetic flux - is responsible on for the sensation of "cogging" i.e. torque ripple in various kinds of electric motors. It is not a dissipative phenomenon and does not have anything to do with the changing average torque demand of an alternator with variation in the power demand of the circuit connected to the terminals.
    The average torque required to drive a generator or alternator at a particular speed is related only to parasitic losses (bearings, etc) in the device
    and the electrical load imposed by whatever is on the output terminals. Physically what's going on is that a greater load (one with lower resistance) allows more current to flow at a given voltage: the greater current creates a larger magnetic field opposing the motion of the rotor.
    Reluctance, in particular the variable reluctance of the motor across its range of travel, is only responsible for small variations in torque and imposes zero average torque on the motor. "



    Thank you.

    Hopefully this crazy thread can now be brought to a close.
     
    P J Thompson likes this.
  8. chippie244

    chippie244 Super Member

    I can't see Handy giving up that easily.
     
  9. P J Thompson

    P J Thompson Active Member

    You could also have highlighted the section directly after the bit that you did, DA.
    The bit that starts, "physically..." and ends with, "...opposing the motion of the rotor"

    :)
     
    Deleted member 33931 likes this.
  10. joinerjohn1

    joinerjohn1 Screwfix Select

    I have never heard such a load of male spherical parts in my entire life Handy. :p:p:p:p:p:p:p:p:p:p
     
  11. It's taken Mr Ha for me to agree with JJ on summat :rolleyes:
     
  12. Mr. Handyandy

    Mr. Handyandy Screwfix Select


    Or you could have highlighted this part:

    "Reluctance, in particular the variable reluctance of the motor across its range of travel, is only responsible for small variations in torque and imposes zero average torque on the motor. "
     
  13. P J Thompson

    P J Thompson Active Member

  14. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    I concede on these parts:

    "With a 100amp alternator installed, we do not drive around with the alternator constantly producing 100amps. When driving a simple car, with no accessories switched on, stock ignition, and the battery topped off with a charge, the alternator produces only about 3amps to 5amps of current! (No matter how powerful the alternator, output is limited according to system demands.)

    And, in case you are wondering, the amount of horsepower used to spin the alternator changes with output. When the alternators produce only a small amount of current, the horsepower drag is very small (less than 1/3 amp). Large amount of output causes more horsepower drag (about 3 or 4 horsepower to produce 120amps output). "


    But not on the wind turbine in free space.
     
  15. btiw2

    btiw2 Screwfix Select

  16. chippie244

    chippie244 Super Member

    Well we are halfway there :p:p:p
     
    longboat likes this.
  17. P J Thompson

    P J Thompson Active Member

    It doesn't matter that the turbine is in 'free' space'. The same effect occurs. Once you are drawing a heavy load (charging a battery) the electromagnetic fields in the turbine offer more inertia and require more force/energy to spin at the same speed.
    That force/energy has to come from somewhere. In an alt it's the engine/fuel. In the turbine scenario it's from the airflow.
    So you either point the car down hill, accept the drag and braking effect or press harder on the go button. :)

    Science stuff gets everywhere see ;)
     
  18. longboat

    longboat Screwfix Select

    So, we've gone from a definate "the alternator sucks the same amount of power from the engine, no matter what the electrical load", to, "ahem, I told youse all along it varied with load".

    If it's any consolation, I also used to think that because the alternator is spinning whenever the engine is, that the torque required to turn it would remain constant.
    In fact, this thread has refreshed my memory about how motors work, something which I did learn and understand many moons ago at college, but had since gone rather rusty.
    A turbine works on the same principle as the alternator though, if it turns freely it produces very little power.
    You need that 'reluctance' to turn if it's going to produce anything meaningful.
     
  19. Mr. Handyandy

    Mr. Handyandy Screwfix Select


    Yes, but it remains that the tube and turbine replaces a solid part of car that offers 100% resistance.
    The hollow tube and fan must be less than this 100%. So it's free. It won't slow the car as much as a solid part.
     
  20. chippie244

    chippie244 Super Member

    It isn't 100 resistance and as btiw2 said you are forgetting/ don't have a clue about the second law of thermodynamics.
     

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