ANSI/EASA Standard AR100

A commonly used and well-respected standard in the electric motor testing industry is the Recommended Practice for the Repair of Rotating Electrical Apparatus (AR100). Furthermore, this standard is provided by the very respected Electric Apparatus Services Association (EASA). It was first approved in 1998 and has since been revised four times with the most recent revision in 2020. For those of you who regularly read the PdMA Tips you might remember we provided an update in 2021. We focused on two important topics including the revised minimum insulation resistance for DC armatures to 5Mohm instead of 100Mohm, and the addition of a new resistance unbalance limit of 1% for form wound and 2% for random wound motors. With no additional changes since the 2020 revision these two items are still the biggest changes to impact the electric motor testing industry. However, another section worth reading and understanding is from section New Windings. “Immediately after rewind, when a high-potential test of the winding is required, it is recommended that the test voltage not exceed 80% of the original test voltage.” This could be an important guideline for your quality assurance team when reviewing your motor repair/rewind procedures.

For a full copy of the ANSI/EASA Standard AR100-2020 visit the EASA website at