According to foreign literature, toroidal transformers can be divided into standard, economic and isolation type and other three categories, various types of features are:
Standard power transformer products:
Series capacity of 8 ~ 1500VA, with a small voltage adjustment rate, full-load operation of the temperature rise of only 40 ℃, allowing a short period of overloaded operation, suitable for the use of high demand occasions. The primary and secondary windings are insulated with polyester film insulation of class B (130℃), which is required to be wrapped with at least three layers of insulating tapes, and can withstand AC 4000V, 1min voltage withstand test.
Economic power transformer products:
Series capacity of 50 ~ 1500VA, in order to ensure the performance on the basis of trying to reduce the cost, for continuous operation without overloading the use of occasions, the operating temperature rise of 60 ℃, the insulation material grade for the class A (105 ℃), when the full load when the output voltage error is less than 3%.
Isolation transformer products:
Series capacity 50 ~ 1000VA, can be divided into industrial and medical equipment with two series. Isolation transformer focuses on its insulating properties, primary and secondary between the polyester film with class B insulation wrapped at least 4 layers, breakdown voltage is greater than 4000V, all primary must lead to the use of double-insulated wires. Transformer maximum temperature rise is less than 45 ℃.
Medical isolation transformer in addition to the above requirements, but also in line with UL544 standards, that is, the primary and secondary windings should be thermally protected, winding and grounded copper shield spacing distance should be greater than 13mm.