Can I combine differant power supplys?

[FriedMule]

I have two PSU with 15V-60A and a 30V-5A but I need 25V-7A. Can I combine the two power supply's and if yes, how, in what order?
Would I be able to make 30V-75A or 45V-60A?

[capt bullshot]

In your particular case, the answer is: No, you can't.

One can parallel supplies, then the maximum voltage is set by the supply having the lowest voltage, and the current ratings can be added. One has to take some precautions, e.g. diode decoupling the supplies.
One can serial connect supplies, then the maximum current is set by the supply having the lowest current rating and the voltage can be added. One has to take some precautions, e.g. reverse protection using diodes.

One cannot simply average the output ratings. Of course, in your particular case, on can build a switching mode step-up converter to make 25V / 7A from the 15V/60A supply. The other one isn't needed then anymore.

[Psi]

Even if you look for a 25V @ 7A PSU to purchase you will have issues finding anything, 25V is an odd voltage.

My suggestion is to look for a 24V 10A psu which has a little voltage adjust pot on it. Those are very common.

The adj pot allows for a little over-voltage. So you should be able to set one to do 25V pretty easy.
There's lots of 24V psus out there, it's a very common voltage and that makes them pretty cheap.

[FriedMule]

Thanks for your great reply, that helped a lot:-)

[Psi]

If you buy an open frame psu, play it safe and mount it in a box so the mains terminals are not exposed.