Electrics/Transformer Safety Basics

Discussion in 'Homework Help' started by AdamOlde, Nov 2, 2008.

  1. AdamOlde

    Thread Starter New Member

    Nov 2, 2008
    Are my assumptions correct?

    '-' means touching.

    Mains L - Human body - GND/Earth = SHOCK

    Mains N - Human body - GND/Earth = "SAFE"

    Mains L/N - Transformer - Human body - GND/Earth = "SAFE"

    Mains L/N - Transformer - Human across transformer - GND/Earth = SHOCK

    Mains L/N - Transformer - Oscilloscope GND Probe = DAMAGE/SHOCK

    Mains L/N - Transformer - Oscilloscope (connected to mains via isolating transformer) GND Probe = "NO DAMAGE/SAFE"

    Mains L/N - Transformer - Mains Tester/Screwdriver = NO MAINS INDICATION/NEON OFF

  2. studiot

    AAC Fanatic!

    Nov 9, 2007
    You are correct

    The neutral is rarely at earth potential in any installation. It is quite possible to get a belt from the neutral, especially in older installations.

    #3 to #7
    I am not sure what you mean by 'transformer' are you referring to the body (core) or terminals?

    In #3 for instance if the body of the transformer is grounded and a live line lead touches the body this should cause a fuse or breaker to blow. So the transformer body would then be unharmful to touch. It is hoped that the fuse would be quick enough to protect if the human was touching before the live lead.
  3. AdamOlde

    Thread Starter New Member

    Nov 2, 2008
    Thanks for replying.

    #3 to #7 Im referring to the touching of the secondary winding/terminal of the transformer.

    The transformer would be an isolating transformer or where the transformer body will not be grounded.

    #6 and #7 Im most unsure with.:confused: