Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Tesla Rotating Magnetic Fields

  1. Sep 16, 2006 #1
    Hello All,

    I was just rummaging through some old Tesla patents I have and I came across patent US381968, which describes different ways to make two-phase AC motors. The setup that I am interested in is on the second page and shows a toroidal core with four coils wrapped on it as the stator. (I believe this setup is also displayed at the Tesla museum too). Anyway, I am still trying to find a simple way to make the 90 degree offset in the signal without using capacitors. I have a couple of ideas about this and thought I would run them past you all.

    1. Simply connecting the coils in series. If all four coils are connected in series around the toroid, will the coils automatically shift the current by 90 degrees?

    2. Winding them all in series and using a specific input frequency. I was thinking about antennas and how they can be tuned to specific wavelengths depending on the length of the wire. Could one conceivably make each coil 1/4 wavelength of the input frequency to get the 90 degree phase shifting effect?

    3. Inductively drive the coils. What if each coil is shorted and one of the four coils is fed with the driving frequency?

    4. Inductively drive the coils as tank circuits. What if I setup each individual coil as a series LC and inductively drive three of the LC circuits using one with the input signal attached?

    Jason O

    Attached Files:

  2. jcsd
  3. Sep 18, 2006 #2
    Hi All,

    Here is some more information. I found a video about Tesla on Google here:

    http://video.google.com/videoplay?docid=2256433507046558974&q=tesla&hl=en [Broken]

    If you look around 15 minutes into it. They show an exhibit at the Tesla Museum of the rotating torous.

    Jason O
    Last edited by a moderator: May 2, 2017
  4. Dec 6, 2011 #3
    I recently built a solid state version of a Tesla patent similar to the one you mention.

    It is variable from 10hz to 10khz. In a nutshell a sine wave from a signal generator feeds into a simple analog differential phase splitter with two outputs (it automatically maintains a 90 degree phase shift - no adjustments necessary) which then feeds the left and right channels of basic audio amplifier and the 2 output channels from the audio amplifier feed the coils.

    Construction details are here:

    I also attached the PDF and the phase shifter circuit diagram to this post.

    Attached Files:

    Last edited: Dec 6, 2011
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook