Page 2 of 4 FirstFirst 1234 LastLast
Results 11 to 20 of 33

Thread: Counter EMF

  1. #11
    Join Date
    Sep 2008
    Location
    UK
    Posts
    6,436
    Quote Originally Posted by ActionDave View Post
    Not universal motors that I am aware of, at least not when they are hooked up to AC; but a DC motor can.
    A series wound DC motor can.
    As can a compound wound one that has lost it's shunt field.
    I haven't witness it happen but I have seen the result of one that did.
    Bit of a mess.

  2. #12
    Join Date
    Feb 2009
    Location
    Durango, CO
    Posts
    3,545
    Quote Originally Posted by Besoeker View Post
    A series wound DC motor can.
    As can a compound wound one that has lost it's shunt field.
    I haven't witness it happen but I have seen the result of one that did.
    Bit of a mess.
    I have not either, but I have heard tales of pieces of shrapnel flying and men diving for cover relayed to me by the motor guru in our shop.
    If Billy Idol or John Denver is on your Ipod go and re-evaluate your life.

  3. #13
    Join Date
    Jan 2008
    Posts
    7,502
    Here is a neat little presentation on the DC motor runaway:
    http://www.wisc-online.com/Objects/V...px?ID=IAU12508
    BB+/BB=?

  4. #14
    Join Date
    Sep 2008
    Location
    UK
    Posts
    6,436
    Quote Originally Posted by mivey View Post
    Here is a neat little presentation on the DC motor runaway:
    http://www.wisc-online.com/Objects/V...px?ID=IAU12508
    Nice demonstration!

    The one I saw was on a winch drive with a compound wound motor. The supply to the shunt field failed. Slightly more complicated.....the shunt field had two different voltages. One for high torque low speed and the other for low torque, high speed. It was in this latter mode that the shunt field supply failed. Not only was the motor in a bit of a state, there was a tangled mess of wire rope.

    It was quite an interesting application, as it happens. It was a tin mining dredger in South East Asia. The dredger floats in a man-made pond* and a bucket elevator digs up the stuff at the bottom of the pond. The dredger moves from side to side on the pond and that's where the winches come into action. There are two forward and two aft on opposite sides of the vessel. They are anchored to the left and right hand banks of the pond. One set, forward and aft, say on the left had side, winches in pulling the vessel towards the left bank. Those on the opposite side which out (render). The bucket elevator thus works across the face of the excavation rather like the operation of a milling machine - just on a little bit bigger scale.

    *Calling it a pond doesn't really convey the scale of it or anything else.

  5. #15
    Join Date
    Dec 2007
    Location
    NE Nebraska
    Posts
    19,221
    Quote Originally Posted by Besoeker View Post
    *Calling it a pond doesn't really convey the scale of it or anything else.
    Understood. There are many people here that would say that you live on the other side of the pond, so the word pond doesn't really carry much size implication sometimes.

  6. #16
    Join Date
    Jan 2008
    Posts
    7,502
    Quote Originally Posted by ActionDave View Post
    ...I have heard tales of pieces of shrapnel flying and men diving for cover...
    Quote Originally Posted by Besoeker View Post
    ...Not only was the motor in a bit of a state, there was a tangled mess of wire rope...
    At first I thought it might be neat to see. I think I'm changing my mind.
    BB+/BB=?

  7. #17
    Join Date
    Feb 2009
    Location
    Durango, CO
    Posts
    3,545
    I was hoping your link would take us to a live demonstration.
    If Billy Idol or John Denver is on your Ipod go and re-evaluate your life.

  8. #18
    Join Date
    Jan 2008
    Posts
    7,502
    Quote Originally Posted by ActionDave View Post
    I was hoping your link would take us to a live demonstration.
    I would need to get me a zoom lens first!
    BB+/BB=?

  9. #19
    Join Date
    Jun 2003
    Location
    NE (9.1 miles @5.07 Degrees from Winged Horses)
    Posts
    5,899
    Quote Originally Posted by ActionDave View Post
    I was hoping your link would take us to a live demonstration.
    Tad bit guilty on that count as well.
    Tom
    TBLO

  10. #20
    Join Date
    Jan 2008
    Posts
    7,502
    Quote Originally Posted by ActionDave View Post
    I was hoping your link would take us to a live demonstration.
    Quote Originally Posted by ptonsparky View Post
    Tad bit guilty on that count as well.
    You guys go first.
    BB+/BB=?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •