SCR for crowbar circuit protection

Discussion in 'The Projects Forum' started by iceman11`, Aug 21, 2009.

  1. iceman11`

    Thread Starter Active Member

    May 4, 2007
    good day guys.

    I am curently designing a crowbar protectino scheme for a robot that is attached to an AC 132kV transmission line, via a current transformer.
    the current transformer steps down the current of the line (from 100 - 1000A) to something that the robot can use, for its own rootics, say 5A. BUT if there is a surge on the line or a lightning strike, the robots electronics need to survive, so i intend to install a crowbar circuit before the electronics of the robot. I am currently choosing an SCR but have no idea how to do so. there are so many confusing parameters:(:confused:

    do i look at drain curent, turn on time, turn off time? and how do i Choose such related values for protection?please see the circuit on, Fig.2 (PRecision Crowbar) , this is the circuit i will be basing my own on, choosing the transistor (SCR) seem sto be a problem.

    Also, since the robot is on a transmission line, it is a bit annoying to go up there and change the fuse if it fires everytime there is a surge/lightning etc, so i intend to use a poly switch, is this viable?

    thanks :>
  2. russ_hensel

    Distinguished Member

    Jan 11, 2009
    Are you aware of the effect of a crowbar circuit. It short circuits the power source. Is this a good idea? Is the poly switch up to the rest of the protection?