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Motor specifications and help

  1. Jan 8, 2008 #1
    I believe a variable frequency drive is the best thing for a three phase induction AC motor. Also I am looking for information regarding gear ratios - is this part of the VFD or is this separate? Any information regarding gear ratios would be helpful. The motor will be used to power a turntable.
  2. jcsd
  3. Jan 8, 2008 #2


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    Welcome to PF, Joey.
    Must be one hell of a turntable for that kind of motor to be used. You'd better be playing Black Sabbath or Metallica, because it would simply be wasted on John Denver.

    I'm not familiar with VFD's. A gearbox, on the other hand, goes between the motor and the load. You really have to be a lot more specific in your questioning, because there are thousands of possible arrangements.
  4. Jan 8, 2008 #3


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    VFD's are usually seen in industrial applications. Companies like Baldor make a lot of them. They are quite nice for control. However, to OP, there is no connection between a VFD and gear ratios. The VFD is the motor drive circuitry. It has nothing to do with the mechanical make up. Every industrial motor I have ever seen has been a straight run shaft. No gearing. You will have to do that separately if required.
  5. Jan 9, 2008 #4


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    Like Fred mentioned, VFD's are for motor control and don't consit of any type of mechanical gears. We use them in the Oil & Gas industry quite often for variable speed drilling top drives.

    Here's a little more information on them...


  6. Jan 9, 2008 #5


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    Try google on -> direct drive record turntable

    The ones I remember did indeed use a vfd on an induction motor.
    They did not use gearing and the turntable was set directly on the shaft.
  7. Jan 9, 2008 #6
    try calling the baldor or leeson motor rep

    try calling the baldor or leeson motor rep
    they will know what is best for your application
    not much else to say without specs for horse power or speeds
    these motors are both great
    good luck
  8. Feb 26, 2008 #7
    Dear joey

    A variable-frequency drive (VFD) is a system for controlling the rotational speed of an alternating current (AC) electric motor by controlling the frequency of the electrical power supplied to the motor.

    Variable frequency drives operate under the principle that the synchronous speed of an AC motor is determined by the frequency of the AC supply and the number of poles in the stator winding, according to the relation, RPM=120f/p

    where, p is the number of pole pairs, f is the ac power frequency.So by varying the frequency the speed of motor can be controlled.

    About the Mechanical reduction or gear ratios in motors reduction units most common is worm wheel and planetary reduction stages and again depends on application.

    Thanks& Regards

  9. Feb 28, 2008 #8


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    Old thread, but hopefully, the OP is talking about a big turntable, like one you might put a car on at a car show. I happened to see a sales rep turning one off at the Philly car show last month, and it looked like about a 1-3hp motor with a belt-drive. Still not something warranting a 3 phase motor and VFD.
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