MOVs as surge protector

Discussion in 'General Electronics Chat' started by electr, Nov 3, 2009.

  1. electr

    Thread Starter Active Member

    May 23, 2009
    I've seen a product which uses 2 MOVs as Surge protector, as can be seen below.

    I dont Understand, why should you connect a second MOV from the NEUTRAL wire to the EARTH wire?

    Isnt the Neutral line connected to the EARTH wire inside the walls, or where the transformer is installed?

    After all, it can't be that both LIVE and NEUTRAL wires are floating, one of them must be connected to EARTH, isnt it?
    Therefore, when a lightning strikes, only the LIVE's voltage rises.

  2. ifixit

    Well-Known Member

    Nov 20, 2008
    * You can get spikes on the neutral from faults in the power distribution system. e.g. short circuits at your neighbours house.

    * The impedance of earth (dirt) is relatively high compared to copper wire so grounding the neutral at the panel doesn't short out all fault currents.

    * The neutral and line can be wire backwards to your equipment, but with two MOVs you will be still protected.

    * Lightning can put pulses on the neutral as well because of the very fast rise times. The inductance in a 100 foot length of heavy gage wire can look like an open circuit to fast edges.