2
\$\begingroup\$

I have a transformer with a single secondary winding but with multiple taps, as shown in the image. It is rated at 4A @ 24V (96VA).

Does this mean that at lower voltages (16V and 8V) it will be able to handle more current than 4A, considering that at any given moment only one of the taps will be used (24, 16 or 8 - but never two or more taps connected in the same time through a load to common)?

Ex: If at 24V it can handle 4A, at 16V will it be able to handle 6A?

I intend to use the transformer for a DC power supply.

Note: Please ignore the inductance values from the schematic

enter image description here

\$\endgroup\$
2
\$\begingroup\$

In short: no.

In "long": it doesn't mean that and, while it may be possible to be so, don't forget that the current capability is directly related to the cross-wire section (area), which means making it generate more than it was planned to will most surely heat it up and, possibly, permanently deteriorate the transformer.

However, seeing that you have 3x8V, it may be possible to connect the windings in parallel, thus granting you the ability to deliver 3 x current, but for that you need to separate the windings so that they are completely separate, then connect them properly in parallel (hot end to hot end), i.e. not in anti-parallel.

Even so, I would discourage this because the windings themselves may not be equal, that is, the 0-6 one may have the average turn length less than the 18-24 one would, meaning that the internal secondary impedances will differ, resulting in other possible cases of deterioration. If, by any chance, you get here, equality may be brought by inserting series resistances on each winding (two at least), at the cost of more losses.

\$\endgroup\$
3
  • \$\begingroup\$ The secondary has taps, not separate windings. You can't parallel them. OTOH, transformers with separated windings are constructed such that you can parallel windings without problems. \$\endgroup\$ – stevenvh Aug 28 '12 at 17:51
  • \$\begingroup\$ One more thing: if it is able to handle 4A at 24V it means that it can handle 4A also at the lower voltage taps, right? I don't need more current. I just need it to be able to handle 4A on all the taps. \$\endgroup\$ – Buzai Andras Aug 28 '12 at 18:26
  • 1
    \$\begingroup\$ @Buzai: Sure, the current handling can be 4A maximum for any given voltage. It's like a pipe: whether it drips or flows, the maximum amount of water running is determined by the pipe's section (and durability). (I can't use two @s)Stevenvh: That's why I said "may" because some tapped transformers can have the taps modified to separate the windings. This only works for those that use a sort of a loop that goes out and back in the winding or similar approaches. This also most probably means that the windings are not equal, hence my last note. \$\endgroup\$ – Vlad Aug 28 '12 at 20:13

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.