Hello all,
we're using a Siemens G120 VFD to control a 3hp inverter rated motor for a small project. To make sure everything worked, we bought about 10ft of Southwire unshielded 10AWG cord to make initial connections. Everything worked fine. Motor is 3-phase running at 208V/7.9A. No choke or filters.
Ordered some 14AWG VFD cable and hooked it up last night. Ran the motor and noticed that the switching noise at around switching frequency (high pitch varies with speed) is now so loud that I almost need to wear earplugs standing next to the motor. Pushing on the fan shroud quiets it down to about half, so it seems to be resonating from there. All of the noise is coming from the motor itself and not the drive. The cable length is only 20ft.
Looking at the drive data sheet, it says maximum shielded cable length of 165ft. Initially I didn't have the shield connected at the drive end, only the motor end (just wanted to do a quick test), but grounding the shield doesn't seem to make a difference. Another thing specified in the Drive datasheet is a conductor cross section of 10-6AWG. However, the drive is rated for 5hp, the motor draws far less than this so didn't see this being an issue.
I'm a bit afraid to run the motor like this as my gut says damage will eventually ensue. I assume some type of electrical resonance here. Anyone have any ideas what's going on and how to mitigate it?
Thanks,
we're using a Siemens G120 VFD to control a 3hp inverter rated motor for a small project. To make sure everything worked, we bought about 10ft of Southwire unshielded 10AWG cord to make initial connections. Everything worked fine. Motor is 3-phase running at 208V/7.9A. No choke or filters.
Ordered some 14AWG VFD cable and hooked it up last night. Ran the motor and noticed that the switching noise at around switching frequency (high pitch varies with speed) is now so loud that I almost need to wear earplugs standing next to the motor. Pushing on the fan shroud quiets it down to about half, so it seems to be resonating from there. All of the noise is coming from the motor itself and not the drive. The cable length is only 20ft.
Looking at the drive data sheet, it says maximum shielded cable length of 165ft. Initially I didn't have the shield connected at the drive end, only the motor end (just wanted to do a quick test), but grounding the shield doesn't seem to make a difference. Another thing specified in the Drive datasheet is a conductor cross section of 10-6AWG. However, the drive is rated for 5hp, the motor draws far less than this so didn't see this being an issue.
I'm a bit afraid to run the motor like this as my gut says damage will eventually ensue. I assume some type of electrical resonance here. Anyone have any ideas what's going on and how to mitigate it?
Thanks,