Brian,It is true that your arrangement would provide the function of an isolation transformer, but that wouldn't do a lot to prevent the transients generated by a TC from propagating back into your house power lines.
Ideal TC EMI isolation circuits use robust L-C power line filter modules plus liberal application of properly sized MOVs for transient suppression. Just running the TC through a long heavy gauge extension cord also helps soak up some transients.
Transformers work in both directions, so spikes generated on the TC side of your isolation transformer setup would just be transmitted back into your house power lines, though with some of the highest frequency spikes somewhat attenuated. Indeed, a properly operating NST will provide line isolation as well, as long as you don't connect the case secondary winding center tap to power line ground.
Line isolation is good for working on old fashioned hot chassis radios, but not a significant benefit for TD operation.
I have seen two matched MOTs connected HV secondary to HV secondary. This provides line isolation and also gives 2X the HV - to - core voltage isolation, useful when you want to stack more than 4 MOTs in series to approximate a pole pig. However, you end up needed lots of these pairs if you are shooting for a 6 or 8 MOT series stack, but by that time, you are just better off from the weight and complexity standpoint just buying a pole pig or potential transformer.
Dave On 6/3/2018 10:50 AM, Brian Hall wrote:
If I take the secondaries off of two MOTs, and put the two 120V coils on a single E core and glue back on the I, then I should have a 1:1 turns, voltage, and current ratio and thus an isolation transformer, right? Would that work for any protection of my house current using one coil as the primary to the wall socket (core as ground to the wall socket) and the other coil to run a 15 kV 30 mA NST (ground or no ground on the NST case?) and then a SGTC? I don't recall the flux saturation details of the core size of your average MOT for this 450 watt NST but I have about half a dozen MOTs, none of which I want power on as-is.. all too aware of the lethal hazards they pose. I've been through an NFPA 70E training course. ---------------------------------- Brian Hall
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