The purpose of the jdcf-66 / jdcf-126 voltage transformer is to convert the high voltage into the standard secondary voltage of 100V or lower in a proportional relation for protection, measurement and instrumentation. At the same time, the use of voltage transformers can isolate high voltage from electrical workers. Voltage transformers work according to the principle of electromagnetic induction, but their electromagnetic structure is opposite to that of current transformers. The secondary circuit of voltage transformer is high impedance circuit. When the secondary load impedance decreases, the secondary current increases, making the primary current automatically increase a component to meet the electromagnetic balance between the first and second sides. It can be said that the voltage transformer is a special transformer with limited structure and use form. Simply put, it is the "detection element".

The type of voltage transformer consists of the following parts. The letters of each part are in line with the expression: J- voltage transformer; D - single phase; S - three phase; J - immersion; Z - casting; Digital - voltage class (KV). Rated primary voltage, as the transformer performance benchmark of the primary voltage value. Rated secondary voltage is used as the secondary voltage value of the transformer performance reference. Rated variable ratio, the ratio of rated primary voltage to rated secondary voltage.

Accuracy level, the level determined by the transformer system, the error should be within the specified limit under the specified operating conditions, the impedance of the secondary circuit, usually expressed as apparent power (VA). Rated load, determine the accurate level of the transformer can be based on the load value.