BMANN06
Member
- Location
- Belleville, ON CANADA
Hey Guys,
Any help here is super appreciated! We have two 700HP DC motors wired in series, controlled by a PowerFlex DC Drive. We start the drive at about 10RPM and the motors start but surge on and off we read as high as 19RPM on our feedback, almost like its hunting.
Here is what I know, I've disconnected each motor at the junction boxes, and disconnected feeders from VFD. Megg'd the motors from GND through brushes, comm and armature and see 1.5+ G ohms at each motor, feeders are full scale. We use a generator connected to rotor as a tach for feedback to drive. Each motor has its own tach but we only use one at a time, they test out ok. Another piece of info, we are just coming out of shutdown, so this drive has been powered off for about 3 months. We had the south motor fail last year and installed our spare, during the this shutdown we had our spare rebuilt and reinstalled on the south. I have also, gone through all control circuits in the LV cabinet and they appear ok. I was on this on the backshift last night, and Rockwell techs have been onsite since about 9am today. I'm heading in and was thinking about pulling apart the SCR banks and testing each of them individually to see if we have an SCR that isn't firing properly.
Any other ideas thoughts, thanks in advance!
Any help here is super appreciated! We have two 700HP DC motors wired in series, controlled by a PowerFlex DC Drive. We start the drive at about 10RPM and the motors start but surge on and off we read as high as 19RPM on our feedback, almost like its hunting.
Here is what I know, I've disconnected each motor at the junction boxes, and disconnected feeders from VFD. Megg'd the motors from GND through brushes, comm and armature and see 1.5+ G ohms at each motor, feeders are full scale. We use a generator connected to rotor as a tach for feedback to drive. Each motor has its own tach but we only use one at a time, they test out ok. Another piece of info, we are just coming out of shutdown, so this drive has been powered off for about 3 months. We had the south motor fail last year and installed our spare, during the this shutdown we had our spare rebuilt and reinstalled on the south. I have also, gone through all control circuits in the LV cabinet and they appear ok. I was on this on the backshift last night, and Rockwell techs have been onsite since about 9am today. I'm heading in and was thinking about pulling apart the SCR banks and testing each of them individually to see if we have an SCR that isn't firing properly.
Any other ideas thoughts, thanks in advance!