As DC motors get larger the circular mils of cable supplying the armature circuit can grow to a size that does not fit in the standard AC/DC current probe. In many cases you have multiple cables attached to a bus bar supplying power to the DC armature and a single DC current probe does not exist (that we are aware of) to encompass this type of configuration. Before you throw up the white flag and opt to not perform a current capture, consider the flexible Rogowski Coil. As long as the supply to the armature is from a DC drive, which is a rectified DC signal, the Rogowski Coil will be able to provide a qualitative analysis of the acquired DC current signal. The minimum frequency response of a Rogowski Coil may be 5-10Hz. The normal full wave rectified DC signal will carry a ripple frequency of 360Hz. This is more than enough variation in current for the Rogowski Coil to acquire a clear indication of the output performance of the DC drive as well as the performance of the DC motor.
