When I base lined the large motors (>1000 HP, 4160 volt) at Beaver Valley Power Station, I took and saved an image of each side. Also, the conditions of the room or outdoors were recorded. Manufacturers use a maximum operating temperature and then recommend not exceeding that value. If a baseline temperature could be compared to another machine of the same manufacturer in the same area, and that temperature was higher, other technologies (vibration, ultrasound, and oil sampling) would be used to help pinpoint the anomaly. Load on the motor was always recorded, as well as scanning the motor breaker compartment. I never used a specific temperature change to tell when a motor had a problem. There were too many variables to consider before making a call on whether a motor was bad or good.
Joe DeMonte itc Thermography Course Instructor |
