glenn1340
30-07-2014, 02:39 PM
Hi guys,
I wonder if any of you have come across the problem of noise in a VFD motor. I have a 306kw VFD motor that has a "screeching noise" ( it has on board SPM monitoring but the trend readings are level). Here`s the thing: It's noisy on application of power ie from 0-3000 rpm and when it off loads and idles. However, as soon as the power shuts off the noise stops instantly even though the motor is still turning.
Searching I found this and it makes sense but I wonder if it actually exists in practice.
"As soon as the motor is started with a VFD, the common-mode voltage imbalance searches for a path to ground, and a parasitic coupling of the rotor and stator windings develops. Once the oil film in the dielectric breaks down, voltage levels increase on the motor shaft, and the lowest impedance path for the current imbalance becomes the motor bearings themselves. Voltage begins to arc across the bearing at high frequencies, leading to electrical discharge machining (EDM)".
By Philip M. Gonski, P.E., Keystone Engineering Group, Inc.
I wonder if any of you have come across the problem of noise in a VFD motor. I have a 306kw VFD motor that has a "screeching noise" ( it has on board SPM monitoring but the trend readings are level). Here`s the thing: It's noisy on application of power ie from 0-3000 rpm and when it off loads and idles. However, as soon as the power shuts off the noise stops instantly even though the motor is still turning.
Searching I found this and it makes sense but I wonder if it actually exists in practice.
"As soon as the motor is started with a VFD, the common-mode voltage imbalance searches for a path to ground, and a parasitic coupling of the rotor and stator windings develops. Once the oil film in the dielectric breaks down, voltage levels increase on the motor shaft, and the lowest impedance path for the current imbalance becomes the motor bearings themselves. Voltage begins to arc across the bearing at high frequencies, leading to electrical discharge machining (EDM)".
By Philip M. Gonski, P.E., Keystone Engineering Group, Inc.