Dear all,
yesterday I managed to have my AC motor running for the first time. Although still on the grid, and just with standard parameters of my SJ300 Hitachi VFD, this was quite a nice moment.
However, I noticed that at low speeds (up to 2 Hz, but dominantly below 1 Hz), the motor was shaking quite noticable. This vibration has nothing to do with any mechanical unbalance, as it was not related to the rotational speed.
The motor (ABB 160 size frame, ca. 120 kg weight) was standing just on the concrete floor. No mounting, but also no elasticity, so the forces must be quite substantial.
Is this effect known or observed by someone? Can this be some internal movements of the coils?? What could be a resolution to counteract this? I am a bit concerned about this, as I want to avoid that I am internally destroying my motor.
At higher speeds (between 10-25 Hz), I noticed a higher pitch tone, seems also not related to the rpm. I assume this is the 6 kHz switching of the VFD, not that concerned about that right now.
On a positive note, I opened the motor (pretty easy with a AC motor), pictures will follow. I had purchased this motor, with Dahlander wiring, with the intention to get the internal start connection brought outside, and use this to go to a delta parallel switching, allowing higher base frequency.
I was very happy to discover that this internal star point did indeed exist
-)), and that it was reasonably simple to reach. After some hacking on the resin soaked binding ribbons (please do wear safety goggles, that stuff is knife sharp!), I was able to free the connection, so now I am up to make a good connection to the outside, and start experimenting with the different switching opportunities.
Happy to hear your remarks and suggestions on the vibrations, regards,
Huub
yesterday I managed to have my AC motor running for the first time. Although still on the grid, and just with standard parameters of my SJ300 Hitachi VFD, this was quite a nice moment.
However, I noticed that at low speeds (up to 2 Hz, but dominantly below 1 Hz), the motor was shaking quite noticable. This vibration has nothing to do with any mechanical unbalance, as it was not related to the rotational speed.
The motor (ABB 160 size frame, ca. 120 kg weight) was standing just on the concrete floor. No mounting, but also no elasticity, so the forces must be quite substantial.
Is this effect known or observed by someone? Can this be some internal movements of the coils?? What could be a resolution to counteract this? I am a bit concerned about this, as I want to avoid that I am internally destroying my motor.
At higher speeds (between 10-25 Hz), I noticed a higher pitch tone, seems also not related to the rpm. I assume this is the 6 kHz switching of the VFD, not that concerned about that right now.
On a positive note, I opened the motor (pretty easy with a AC motor), pictures will follow. I had purchased this motor, with Dahlander wiring, with the intention to get the internal start connection brought outside, and use this to go to a delta parallel switching, allowing higher base frequency.
I was very happy to discover that this internal star point did indeed exist
Happy to hear your remarks and suggestions on the vibrations, regards,
Huub