Noise in large high voltage induction motors (500Hp and above) may be windage or magnetic in nature. Usually large high voltage induction motors induction motors are custom built and tailored to meet customers demand. In large high speed induction motors sometimes it is difficult to isolate windage noise from magnetic noise as the generated frequencies are similar in magnitude; hence reducing noise after motor is manufactured becomes extremely challenging. This paper will present the noise troubleshooting case study of 10,000Hp induction motor that shows overall noise of 100 dB during the factory testing. A variety of tests (e.g unloaded, variable speed, coupled loaded test and also test motor driven as load) were performed to isolate magnetic noise from air borne noise. Noise FFT data was collected to identify peak noise generating frequencies. Sound intensity and sound pressure data were also collected to calculate overall sound power level. After identifying the cause of noise, motor frame design was modified which results in overall noise level of 85 dB.
