Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx> Hi Justin,On an ideal transfomer, the secondary load (open circuit in this case) will reflect to the primary by dividing the load impedance by N^2. So an open circuit secondary will cause the primary to look open circuit as well (for the ideal transfomrer). For a real transfomer with secondary open, the primary will look like an inductor (low resistance but reasonable reactance). Transformer models put this inductance in parallel with the ideal primary. If the MOT is saturating (too many volts per turn for the core area), this inductance will be significantly reduced. The suggested test at a lower primary voltage is a good one. (see below)
Gerry R
Original poster: Justin <rocketfuel@xxxxxxxxxxxxx> Greetings! I have a rudimentary question that's been nagging me every since that pole pig discussion of last week. Experience and my gut tell me that an open secondary will draw very little real current on the primary side. What I can't figure out is *why* that's true because from one POV that primary should be a low resistance short circuit and current should be through the roof! Is it the impedence of the coil + core that keeps things from going bananas? Some sort of magneticlaly induced EMF that opposes the current flow? My gut also tells me that if I simply make a coil out of wire and stick it in my wall outlet the current would definitely be there.
An air core coil plugged into the socket will draw current because it looks like an inductor (smaller inductor than with an iron core).