Reactor for error compensation is mainly used for load error adjustment of power type voltage transformer.Since the reactance of reactor for error compensation needs matching the primary and secondary leakage impedance of power type electromagnetic voltage transformer

therefore it is required to have high quality factor（Q value）.In this paper

the error compensation principle of the power voltage transformer is introduced

the generation mechanism of AC resistance of the iron core reactor at different air gap is analyzed and the test system is set up to test the hysteresis loop of the iron core at different air gap length and its corresponding inductance value and AC resistance.To master the relationship between the technical parameters of the iron core reactor and the air gapand adopt the iron core reactor with air gap for the compensation of one set of 110 k V 60 k VA power voltage transformer.It is shown by the test result that the longer the air gap of the magnetic circuit is

the smaller the permeability and the smaller the corresponding AC resistance and inductance are.However

the more difficult the core is to saturate

the larger the dynamic range of the working current with stable impedance is.The adoption of air gap core reactor is used to compensate the error of power voltage transformer.The compensation results show that the error can meet the requirement of 0.2 grade error limit.