11-02-2015, 12:11 PM
(11-02-2015, 11:55 AM)Skywave Wrote: What are doing is creating your own mains supply, completely floating wrt what comes into your house. You are using a double-wound TX to do so.
Exactly: that's the whole idea. And a balanced 120-v. - 0v. - 120-v. supply too, fed from an RCD with suitable fuses fitted also.
But if, as stated in post #5, you have not connected the centre-tap to mains earth, then you have not created a balanced supply - you have created a floating supply with the ability to make the metal cases of any class 1 equipment plugged into it float up to 120V, as explained in post #10.
Moreover, if a "phase" of this supply is connected by accident to mains earth, then I don't immediately see how an RCD between the transformer secondary and the sockets can detect an imbalance. Well, not until you touch the metal case of a class 1 device (which will be at 120V at this time).
The earth of the outlets must be firmly connected to mains earth for this arrangement to be safe. Simple as.
Out of interest, what does this transformer supply? Just DUT, or DUT plus test equipment?
