Why use a 1000:1 transformer instead cascading three 10:1 transformers?

Question

I was researching different ways to make a high voltage DC-DC power supply in the 20 kV ~ 30 kV range, with output of a few tens of micro amps. The purpose is for testing isolation and resistance to ESD on panel mount components.

One common factor I seem to run across in the DIY electronics world is people using transformers with very high turns ratios. They can't be made by hand and are often salvaged from old CRT monitors/TVs. While that works for a one-off design, it's not really suitable for designing a reproducible product.

Why not just use several transformers in series with lower turns ratios instead of one transformer with a very high turns ratio? For example, instead of using a 1000:1 transformer, use three 10:1 transformers.

10:1 transformers can pretty easily be wound by hand. It's likely cheaper to make (at least from a coil winding standpoint), and as a bonus you get multiple stages of isolation between your input and output.

I am sure there is some practical reason for it, but it's not yet obvious to me.

Answer 1

Why not just use several transformers in series with lower turns ratios instead of one transformer with a very high turns ratio?

Every magnetic core has a maximum volts per turn that can be applied at a given frequency without saturation. If your core has, say, a maximum of 1 volt per turn, at your desired frequency, then you must have 10000 turns on any winding that has 10000 volts on it. If your several transformers have the same sized core, there is no advantage turn-wise for not putting your 10000 turns on first transformer, and be done with the step-up process.