how to detect/test a rotor defect?

This is sort of a vague question but I'd think the first sign of trouble would be excessive heat or vibration or both.

more information please

describe the rotor

describe the fault

its dificult to give you an answer based on the limited information given

Hello KevinL,

good option for detecting broken or cracked rotor bars of motor on-line and under the load is instrument with MCSA or motor current signature analysis.

Sometime vibration alalyzer can identifies rotor bar defect with varuing magnetic field and vibration around running speed or * haystacks* and around high frequency vibration known as rotor bar pass frequency.

People with expirience can see bad rotor by simply swinging needle of amper meter.

Good luck !