BPFO with running speed sidebands

It could be due to a significant unbalance. The impact should be stronger when the mass center hits into the defect and weaker when is opposite.

Anyway, I suppose the modulation is not as visible as in the case of an inner race defect and the sidebans should be small

Agree david its the phenomena of ampltiude modulation here the carrier frequency is BPFO and the modulating frequency is running speed..

In BPFI its quite obvious as defect is going in the load zone as per shaft RPM so running speed sideband will appear around BPFI..

but outer race is stationary so defect should not modulate by running speed..

But In some cases but not specific cases BPFO will have running speed side bands..some of them is listed below but I am not sure why & how it is modulated?

1. There is severe damage in outer race.

2. Unbalance

3. Ecentric rotor 



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