Hi all
I have two identical toroidal transformers. Purchased on the same day, so probably same batch.
They have 2x 115V AC primaries, and 2x 15V AC secondaries. I need to find a way to double their voltage, while keeping them in the same common supply. Each one is capable of 15VA.
I was playing around in the software, and came up with two different combinations. See the Imgur link here.
Please let me know which would be the best method to connect the primaries.
I have two identical toroidal transformers. Purchased on the same day, so probably same batch.
They have 2x 115V AC primaries, and 2x 15V AC secondaries. I need to find a way to double their voltage, while keeping them in the same common supply. Each one is capable of 15VA.
I was playing around in the software, and came up with two different combinations. See the Imgur link here.
Please let me know which would be the best method to connect the primaries.
Wire the primaries in parallel and secondaries in series additive. If when wiring secondaries the net voltage is null, reverse only one of the primaries or secondaries but not both.
For 240VAC line voltage, each transformer should have its primary windings in series.
Then connect the series windings in parallel, to the AC line (like the first drawing).
Then connect the series windings in parallel, to the AC line (like the first drawing).
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Try to never parallel secondaries of transformers. It may be a recirculating current of unpredictable value and one of them may become overloaded, this includes simmilar units, because one of them may have a fraction of a volt of difference sufficient to establish such internal current through the relativelly small output impedance of step down traffos.
Yes, do not parallel secondaries that are on separate transformers,
but it is perfectly ok to parallel secondaries that are on the SAME core.
but it is perfectly ok to parallel secondaries that are on the SAME core.
A seperate bridge rectifier on each transformer eliminates this problem.
Wire each individual transformer for 240V primary (windings in series). Then, T1 and T2 primaries are wired in parallel to a 240V source.
Secondaries CAN be wired in parallel if you want, including from different transformers. Small changes in output voltage just cause a little extra VAR flow between transformers (one leads, the other lags). They self-correct, allowing parallel operation. It is simple orthogonal math that recognizes reactive current flow across a reactance causes significant voltage drop - this is to your advantage when paralleling transformers. The additional current flow due to circulating VARs DO decrease effective capacity - but for similar transformers (you said they were identical) you would not expect decreased capacity more than say 95% of rated.
In the power industry we parallel transformers all the freaking time, including different transformers having different impedances with different kVA ratings. The equations are fairly straightforward that tell you how they share current, how the VARs flow, and what decreased capacity results. It does not harm them.
I have software that can predict the behavior to a high degree of accuracy if you have a decent model. But it's really not necessary if the transformers are the same build.
Secondaries CAN be wired in parallel if you want, including from different transformers. Small changes in output voltage just cause a little extra VAR flow between transformers (one leads, the other lags). They self-correct, allowing parallel operation. It is simple orthogonal math that recognizes reactive current flow across a reactance causes significant voltage drop - this is to your advantage when paralleling transformers. The additional current flow due to circulating VARs DO decrease effective capacity - but for similar transformers (you said they were identical) you would not expect decreased capacity more than say 95% of rated.
In the power industry we parallel transformers all the freaking time, including different transformers having different impedances with different kVA ratings. The equations are fairly straightforward that tell you how they share current, how the VARs flow, and what decreased capacity results. It does not harm them.
I have software that can predict the behavior to a high degree of accuracy if you have a decent model. But it's really not necessary if the transformers are the same build.