Timeline for Why would an AC motor heavily shake when driven with certain frequencies?
Current License: CC BY-SA 4.0
10 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Sep 8, 2019 at 21:40 | comment | added | Ömer Gezer | I'll be sure to measure currents drawn by each phase in current stable state tomorrow and report here | |
| Sep 8, 2019 at 17:06 | comment | added | TimWescott | Good question! If there's a resonance at the system's synchronous frequency that would show up as a current imbalance, but it does seem extreme. Maybe the OP will be good enough to measure the now-not-vibrating motor and see if it's still there. | |
| Sep 8, 2019 at 7:07 | comment | added | crobar | how does this explain the current imbalances? | |
| Sep 7, 2019 at 18:48 | comment | added | TimWescott | I suspect you had just successfully dodged the resonance frequencies, and possibly were always above the first resonance. It's actually a thing on some aircraft tachometers to have red zones that are below the maximum speed that you're only allowed to sweep through, but never dwell on, because there's airframe resonances at those points. | |
| Sep 7, 2019 at 18:40 | comment | added | Ömer Gezer | @TimWescott It makes sense that when ζ gets small, the resonances will be more apparent, but it was counter-intuitive to me since i've run about 20 different AC motors the same way, unmounted on a table, and it's the first time i've seen such a thing. There were also motors that are similiarly sized, similiarly massive and rated for a similiar power among those 20. | |
| Sep 7, 2019 at 17:56 | comment | added | TimWescott | I'm not sure how far along you are, but consider a mounting system that responds to force as a typical 2nd-order LPF: \$\frac{P}{F} = \frac{(1/K) \omega_0^2}{s^2 + 2\zeta\omega_0s + \omega_0^2}\$. Now let \$\zeta\$ get really small, and tell me what happens when \$s = j\omega\$. With structures, it's hard to make the damping for the resonances large, so the usual effort involves making the resonances high enough that they won't be excited. | |
| Sep 7, 2019 at 17:35 | comment | added | D.A.S. | All mechanical parts have many mechanical frequency resonances and when excitation spectrum times Q of resonance is amplified , you get vibration g. loading acts as a filter with real and reactive LPF features and also possible resonance. Fourier analysis , Nodal Analysis, are common maintenance damage prevention and design improvement methods. e.g. bearing wear in large machines, generators, motors. turbines | |
| Sep 7, 2019 at 17:18 | vote | accept | Ömer Gezer | ||
| Sep 7, 2019 at 17:18 | comment | added | Ömer Gezer | So I mounted the motor in it's original configuration, in the lathe, connected to the spindle with the belt. The shaking is almost completely gone as you would suggested. This is the first time I've seen such a thing and it's been a good experience. Thank you for all your suggestions. If you have any other examples on the topic, I'm interested in seeing them because I'm studying in system dynamics masters and really interested in such situations. | |
| Sep 7, 2019 at 17:04 | history | answered | TimWescott | CC BY-SA 4.0 |