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Alternistor quadrants and specs

Discussion in 'General Electronics Discussion' started by fastline, Nov 11, 2013.

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  1. fastline


    Aug 9, 2010
    I am trying to repair a battery charger with an alternistor driven front end and just a step down transformer and rectifier back end. T1 is shorted to the gate on this alternistor spec'd as a Q4025P. I must ensure that was I put back in will work. I also have some concern with the optocoupler due to the short but they are at the same potential? so is that really an issue? All series resistors are still good.

    It was my understanding that all alternistors were made to only operate (maybe just turn on?) in quadrants 1-3? I was going to replace with a Q6025P5 by little fuse but was not sure by the data sheet if there would be a IV quadrant operation?

    As well, the "5" on the end of the PN indicates a sensitivity of 50ma and the Teccor sheet indicates 80ma. I am not sure if the increase in sensitivity could be a concern?

    Attached Files:

  2. TorontoBob


    Oct 6, 2013
    Littlefuse bought Teccor.

    The "sensitivity" is the maximim current needed to trigger it, though it could easily be triggered with much less current, so there should not be any problem with one that has a somewhat lower trigger current.

    I may be a little rusty on this not having worked with them for quite a while, but if you are using a triac driving optocoupler, you are only going to be triggering in quadrants I and III.

    Triacs/Alteristors may be Q-IV triggered but it is not specified by the manufacturer, takes much more current that Q-I and Q-III and the variability of how much trigger current in Q-IV makes it an unreliable method of trigger and so to be avoided.
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