What is the reason for using high KVA transformers in electrical heaters?

[Umar Awan]

Note: I have a feeling this is below Electrical Engineering requirements, but I couldn't find a more suitable category, so I think I'll extort the advantages of a forum base with electrical understanding more than I think may be required(ofcoarse I know very little about the field, so I may fall short first, knowledge wise).

Backstory: I have been planning to build a thin film deposition setup for coating my telescope lenses with aluminium. The Flash evaporation process requires a very high current and my whole setup has got me running short on my budget. I figure I could save a quite a bit of money if I cut out on that big high KVA transformer I have requested a quote for recently.

Question: What is it that forces electrical heater manufacturers to buy such high KVA transformers for a high current when the same amount of current could been drawn from a cheaper, small KVA transformer using more coils in the primary?

I figure coil losses would likely be the negligebely same either ways, so could it somehow possibly *fingers-crossed*be the physical limitation of fitting a high gauge coil in a small transformer(or a lot of primary coil)? Or is it because say, adding infinitely(very large) many primary windings may get to the point where resisitive losses in primary cost more than simply buying a transformer with more KVA? Or is it something to do with the transformer core?

I would also appreciate it if there are some formula's for calculating when its prefferable to stick to High KVA transformer, over adding a very large number of primary windings and increasing costs more than high KVA transformers possibly could.

Please don't get discouraged with the effort of teaching my V=IR if I have made some basic errors. Hehe, I may be worse. Also forgive my apologist overtone and head to the reply section

Thanks in advance.

Umar Awan

 

[rbelli1]

Adding more coils to the primary and not the secondary will give you a lower voltage at the secondary. The power output of a heater is V²/I. Lowering the voltage lowers the heat output dramatically.

Adding more to each while reducing the physical size of the transformer will give you a lower VA rating as that is strongly dependent on the gauge of the wire. More turns in a smaller package necessitates a thinner wire.

I think that should allow you to answer the rest of you questions.

BoB