A machinery train has vibration at the first torsional critical, but excited only near a certain speed. It is a "direct torque control" variable speed, 4-pole induction motor with 50 Hz utility grid frequency. The speed for high vibration events appears to be where:
Difference between 2 times...
(fixed title)
With a permanent magnet AC motor, for reducing noise, should the stator slots be completely filled? If so, is it best to use magnetic, non-magnetic, or semi-magnetic material? Also, are there service shops that can treat stators that have unfilled slots?
I posted this in Electric Power Eng'r forum - no response:
We used a step-up voltage transformer for a test run with a variable-speed 60 Hz motor. There was an odd subsynchronous frequency near 9 Hz found in the converter output current signal. Could the frequency come from the step-up transformer?
We used a step-up voltage transformer for a test run with a variable-speed 60 Hz motor. There was an odd subsynchronous frequency near 9 Hz found in the converter output current signal. Could the frequency come from the step-up transformer?
A speed increasing gear has a shaft displacement probe on the pinion. During operation, there is subsynchronous vibration on the pinion that changes with load. Frequencies are at one times and two times bull gear frequency, with much smaller amplitudes at other harmonics of bull gear frequency...
Has anyone experienced non-repeatable motor vibration, with motor running solo? One symptom is that vibration is higher initially if the motor sits for a while. Motor is an 1800 rpm induction unit with pressurized hydrodynamic bearings.
Has anyone experienced non-repeatable motor vibration, with the motor running solo? One sympton is that vibration is much higher initially if it sits for a while. Motor is an 1800 rpm induction motor with presurized lube hydrodynamic bearings.
