220v transformer can withstand voltage how much?

Look at the transformer is used in what equipment, at present our company to do the 220V toroidal transformer voltage is the highest 10,000 volts, this product is used in aerospace equipment; also did four thousand volts - five thousand volts, is applied to medical machinery; these two kinds of equipment on the voltage requirements are relatively high. And the other ones are to do 2500V voltage, can be customized according to the requirements.