8/10/2009 5:41 PM | |
Posts: 4 Rating: (0) |
I have a Micromaster440 GX frame drive running a 150kW vertical pump motor using a 3-phase, 480V, 60Hz supply. The drive has operated well for six years, but has recently suffered many F0020 faults (Mains Phase Missing). In a reply (by diwa) to another post (by RBM), it was suggested that the sensing of F0020 is based on the ripple of the DC bus, and the drive may operate well until motor speed increases. This seems to be what is happening to my drive, as none of the AC mains phases are truly missing. The DC bus seems to have too much AC ripple, and beyond a certain speed, the drive faults on F0020. I tried checking the rectifier diodes per the previous post, but Iwas unable to locate an open diode using an ohmmeter. I believe this drive may instead use SCRs as rectifiers instead of diodes, as each rectifier "package" appears to consist of two devices (SCRs?) with two, twisted pair cables running between each package and a printed circuit board attached to the left of the rectifier devices. Those look like they could be gate and cathode leads of an SCR, and that the board on the left may be a firing board of some kind. Also, there's a red LED illuminated on this board, and I don't know what it means. I connected a power quality recorder to the input of the drive and the input current waveforms are not normal. It looks as ifone of the phases is not rectifying in the positive half-cycle. I have almost no experience with this drive, and would like to know if it has SCRs or diode rectifiers, and if anyone can tell me what that red LED means? I believe the problem is on the input rectifier rather than the PWM output (which looks OK). Thank you! RWPH AttachmentRWPH2.zip (169 Downloads) |
8/11/2009 6:37 AM | |
Posts: 21 Rating: (1) |
Dear RWPH Ask your are asking about RED LED, I think is for VFD fan supply indication. (not 100% sure). I will go through your problem then try to respond you. |
8/12/2009 2:04 AM | |
Joined: 4/7/2009 Last visit: 4/27/2022 Posts: 16 Rating: (0) |
Hi RWPHI have seen this MM440 Fault before in siemens forum threads. The guy who had this problem checked all the electronics boards though he couldn’t find the problem. Finally he cleaned all the electronics board and drive went ok.In your case also the drive had been working for 6 years. It seems common problem with MM440 when they run in a dusty environment for few years.Before you pull apart electronics components (SCR, diode or IGBT) I suggest you to clean all the components (remove the dust) and give it a go. |
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8/13/2009 3:17 PM | |
Joined: 9/20/2006 Last visit: 3/5/2024 Posts: 307 Rating: (95) |
Please take precaution when removing the power block it is very heavy. diwa. |
8/20/2009 10:04 PM | |
Posts: 4 Rating: (0) |
Everyone: We removed the powerblock, and discovered that the connection between the + DC busbar and the phase 1 (front-most) rectifier thyristor module was very loose and arcing (photos attached). This is exactly what the PQ recorder waveforms were suggesting (no positive DC pulse from phase 1). Now I need to clean up the arced busbar and look into replacing the thyristor module (Siemens SKKT 330/16 E Semipak3......but I think it ismade by Semicron, though Seimens, not Semicron, appears on the module itself). It doesn't look too difficult to replace this thyristor module (4 screws and some heat sink compound). Has anyone out there ever replaced one of these? Thanks all, RWPH AttachmentPhotos.pdf (204 Downloads) |
9/30/2009 9:25 PM | |
Posts: 4 Rating: (0) |
Hello all: We finally received the replacement SKKT 330/16E SCR modules, removed the powerblock, and replaced the SCR module that was damaged by arcing due to loose connection to the positive DC busbar. The drive is now running the 200HP motor and all six SCRs are contributing to the DC bus voltage (not just five), so we've had no more F0020 Mains Phase Missing faults. The Semikron Semipack 3 SKKT's have been redesigned (photo attached), and there is now much more contact surface area between each busbar and the SKKT. But, the red LED on the circuit board that (amongst other things) controls firing of the six SCRs is still illuminated, and I still don't know what it means (the identical drive running the other motor does not turn on this LED). I've attached a photo of this LED as well (page 2 of PDF attachment). The only other difference I see between the two drives is that the other one has input current pulses of roughly equal magnitude, whereas the one I just worked on has input current pulses of different magnitudes. I don't know that it matters, and the motor seems to be running happily and no more F0020 faults. Oh, I was incorrect earlier when I said the SKKT's were labelled Siemens instead of Semikron. All of the SKKT's (old and new) say Semikron, not Siemens. Thanks to all of youwho offered advice;I appreciate the help! RWPH AttachmentSKKT and LED Photos.pdf (182 Downloads) |
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