Abstract: A DC measuring circuit for power rectifiers is described wherein primary line current is utilized to measure direct current output. In the measuring circuit line current transformers are connected to a multiphase instrument rectifier through a phase shifting current transformer which is adjustable to compensate for difference between the primary to secondary line current phase shift characteristic of the power transformer and any phase shift in the line current transformers. By such compensation the average value of rectified primary line current in the measuring circuit is maintained independent of the commutating angle of the rectified power current.