Hello. Is my brand new 100a autotransformer defective?! It is putting out 120v and 114v on each leg.
Can I fix this? What do I do?
Hello, firstly, what is exactly the problem if the balance isnt 100% equal?, due to current unbalance between the legs this is often created. a few % difference will not cause any issues for loads connected Beside this, how are you using the AT ?
As step up/step down or as load balance?
George did you ever find resolution on this?
It looks like you are simply experiencing the limitations of the autotransformer in terms of regulation. With transformers, the dominant source of voltage drop under load is often not the resistance of the windings, but the imperfect magnetic coupling between them. This can be modeled as so-called (imaginary) leakage inductance placed in series with a winding of an otherwise perfect transformer.
A consequence of the transformer's source impedance being predominantly inductive is that with resistive loads (load current in phase with voltage), the voltage drop in the leakage inductance is 90 degrees out of phase with the winding voltage. When you add these two together vectorially, a significant voltage across the leakage inductance causes only a small effect in the magnitude of the output voltage.
With an inductive load, the voltage drop across the leakage inductance is in phase with the winding voltage, and subtracts directly from it.
So here is the point: motor loads (like an a/c compressor or fan) which are not purely resistive (another way of specifying this is to say the power factor is less than 1) can cause significantly worse regulation in a transformer than resistive loads. I suspect your system would perform better with a purely resistive load drawing the same current.
This is of interest to me because I'm considering this autotransformer to provide split phase AC from a 240V Quattro. But since Victron don't specify crucial technical data about the autotransformer, the only way to find out how well it will work seems to be to buy one and try it ... or to read of other's experiences on this forum.
18 People are following this question.