I know it depends on model somewhat but I am trying to get estimate as to what the secondary inductance would be for a toroid transformer that is 120 VAC 500VA with center tapped secondaries. I am not looking for an exact value only a range of values so that I can verify if what I find is correct.
Output is 24VAC center tapped. I am after inductance looking back into secondary with inputs shorted. I know how to get it. I will use s siggen in series with a resistor and measure the voltage arcoss it. From there the calculation is based on the complex impedance Z, I was just looking for a an approximate value to confirm my calc is correct but I think the answer is it should be in the range of a Henry within an order of magnitude.
Large toroidal transformers usually have only a few percent difference between the unloaded and the fully resistively loaded output voltage. The difference is partly due to wire resistance and partly to leakage inductance.
500 VA and 24 V means a current of 20.8333... A. Assuming that your transformer gives 25 V with no load and 24 V with full resistive load, the drop that the 20.8333... A causes across the leakage inductance must be less than 7 V (square root of (25 V)^2 - (24 V)^2, because the voltage across the inductance will be 90 degrees out of phase with the voltage across the load resistor).
Hence, the reactance of the leakage inductance must be less than 0.336 ohms. When the mains frequency is 60 Hz, that boils down to a leakage inductance well below 891 uH.
500 VA and 24 V means a current of 20.8333... A. Assuming that your transformer gives 25 V with no load and 24 V with full resistive load, the drop that the 20.8333... A causes across the leakage inductance must be less than 7 V (square root of (25 V)^2 - (24 V)^2, because the voltage across the inductance will be 90 degrees out of phase with the voltage across the load resistor).
Hence, the reactance of the leakage inductance must be less than 0.336 ohms. When the mains frequency is 60 Hz, that boils down to a leakage inductance well below 891 uH.
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