Proper use of the core tester
Prior to rewinding it is advisable to assess the condition of the core iron of stators, armatures and wound rotors. The assessment is performed by a core test, which magnetizes the core to a prescribed magnetic flux density. The core tester can do more than just probe for hot spots; it can give an indication of the overall core condition in terms of watts per pound (or watts per kilogram) of loss. A detailed explanation of stator core testing is given in Tech Note 17, so that won't be repeated here. Our objective is to explain the proper uses and interpretation of core testing using a core tester.