The application of a powdered epoxy dielectric coating to D.C. machines

Certain areas of D.C. rotating machines have a performance record of decreasing insulation resistance with use, resulting in increasing creepage current. This condition has been most prevalent in the riser area of rotors. The riser area refers to the open connecting bars, risers, between commutator and rotor coils and adjacent support members and core plates. (See Figure 1.) Bare risers are a design characteristic of most larger D.C. machines over 22" rotor diameter, which cannot be practically avoided.