Back EMF question

Discussion in 'The Projects Forum' started by Pika, Oct 27, 2010.

  1. Pika

    Thread Starter New Member

    Jul 27, 2010
    Hi Everyone,

    I was asked to design a solenoid "that can operate with a back EMF limited to -37.6 VDC". My first thought is, this doesn't make sense. why design for a back EMF when you can just get rid of it? Is this number to calculate which diode to use to prevent EMF? Can you help me interpret what this means?
  2. benjamin21open

    New Member

    Oct 7, 2010
    Which one do you mean you'll remove, the EMF or the solenoid?
    If you remove the solenoid where would you get your power start?
  3. Kermit2

    AAC Fanatic!

    Feb 5, 2010
  4. marshallf3

    Well-Known Member

    Jul 26, 2010
    I used to have a rule of thumb for snubbers across inductors that I went by but it was recently shot down due to some further study.

    The EMF can rise as high as 10x the normal operating voltage peak (I used to go by 4) thus the diode should be able to handle fairly repetative pules of current also about 10x the peak current the inductor normally sees.