[Amps] More on two pin 220vac

[peter chadwick]

The neutral is probably grounded at the distribution transformer. That's likely to be a Y secondary and the centre point is 'grounded' and forms the neutral. Depending on the load and how much resistance there is in the neutral, at any point along the distribution, the neutral voltage will rise above ground to some extent, so quite often, additional grounds are provided for the neutral. The problem comes if the neutral is ruptured: then the 'load' side of the break is connected through the stoves, A/C, radio gear etc to the live side of the line and the neutral, under these fault conditions is up at line voltage with respect to ground.

With Protective Multiple Earthing, provided there is enough distributed grounding of the neutral, that isn't a problem. Where the neutral is connected to the house ground wiring, then you can get a problem, because the stove, A/C etc would love that ruptured neutral to have a good ground connected to it. If that ground is the external radio ground, all the fault current wants to go there through the cable in the wall and the transceiver power cord which can't take 50 or 100 amps....for very long, anyway.

So here, it is allowed for the property earth to be separate from the supply 'earthed' neutral - and that's much safer in the ruptured neutral situation.

But different countries have different methods. At one time (and maybe even now) some outback properties in Australia used a ground return instead of a neutral.....

As they say, 'there's more ways than one of skinning a cat' - although my cats don't believe in any of them!

I think Charles should firstly check the schematic to make sure that there is nothing getting power from one side of the line and chassis - although that's not been allowed for years and the amplifier probably wouldn't work anyway. The use a meter to check that BOTH mains leads are a very high resistance to chassis - many megohms.

Secondly, check the wiring to make sure the interlock wiring is as it should be - and Lou has given some pretty definite directions on that.

73

Peter G3RZP





73

Peter G3RZP