Using transformer with 3 28.5V secondary windings to supply 57VAC/80VDC

I have a transformer (toroidal) that has 3 isolated 28.5VAC secondary windings.

2 of the windings are in parallel with each other with the third winding in series to supply 57VAC to 2 DM860H stepper drivers.

This means one winding is handling double the current of the others.

Right now there is no problem, as the winding can power 2 drives without any issue.

In the future, I plan to add a third stepper driver.

Can I get away with overloading that one misfortunate winding, Or should i place more load on the 2 parallel windings using a voltage-doubling rectifier.

You just have to respect the max current of the transformer ! Tommy say metal core transformers can withstand a lot of overload, he's right, but I would think a toroidal one is not this type, and you could have magnetic saturation.

If you don't know your load current, just put a fuse to protect the output and you will see.

But mostly equal current load across all windings seems like a good idea, right?

Plus I have to make a flyback diode board because the motor drivers I have, while very good, have either no flyback diodes at all or only half (4) flyback diodes.

Making a power supply on the same PCB is not that much extra work.

I was wrong with saturation. I'm used to small ferrite toroidal transformers wich are sensible to saturation, but your is surely iron core. Like Tommy said, the limit is the temperature.
And even with ferrite, it's only one magnetic circuit, so saturation would only appear when the total windings current exceed the maximum of the transformer.
We don't care of unbalanced current between windings.

Tommy advice is to overload it and check the temperature, I agree it works, put the right fuse after test on the output and then. Are you even sure you will overload it ? Maybe not !
I would although consider to change it because I think it's a small one (you don't say how many amps you have), and I have many unused transformers. Maybe you don't. Have a look around you, it's easy to find some...

Doing a power supply.. For me no, if you put the three in series you will have 90VAC, better to use directly 120VAC or 240VAC in this case.

But once again, I assume your transformer is a small one (300VA ?), it's not the same if it's a 2kVA one, but in this case you wouldn't need to worry for the third driver.

I mean like rectify from the 2 parallel 28.5 windings and then double the voltage the way that power supplies with a 110V/220V switch do.

From what I can see, there is absolutely no writing or info about the transformer at all.

I have no clue what the transformer can supply.

No idea.

There is no sticker on the side of the toroid.

Is it common to place the sticker on the top (where is is covered by the mounting plate)?