Good morning, everyone. I have a few questions regarding the 11kV Siemens motor's high vibration issue. During the testing phase, were the motor shaft and coupling element balanced on a testing unit? Did you run the motor after installing the rotor with half of the coupling element, and if so, what were the vibration levels? Did the vibration levels increase after coupling to the load? Were the motor's sleeve bearing clearances within specifications? It is standard practice for the motor to have one insulated bearing to prevent looseness issues between the bearing and the housing. Improper insulation could lead to electrical current flow damage over time. Please advise on possible tests or solutions if you have encountered similar problems in the past. Thank you.
- 04-10-2024
- Jasmine Howard
Edited by Vinny Prinu Vincent on July 18, 2023 at 08:00 AM Hi Raffie, the rotor was balanced with a half key and a solo run was conducted in similar conditions. However, the customer only sent the motor without the coupling half. The sleeve bearing clearance was within specifications, and we placed NOMEX between the bearing shell and housing to secure it. Despite insulation and carbon contact on one side, the vibration remained high during the test run.
Raffie Musaib-Ali inquired about the high vibration levels of an 11kV Siemens motor. It is essential to balance the motor shaft with the coupling element and test the motor before and after coupling to check for vibration levels. Ensuring proper bearing clearances and insulation is crucial to prevent damage from electrical current flow.
Regarding the overhauled and rewound 11kV Siemens motor with high vibration issues, various tests and adjustments have been made. The presence of softfoot at the motor base was corrected with shims, and tests on the rotor and stator showed no issues. Despite efforts to insulate the bearings, the vibration levels persisted, particularly at the center of the stator frame. Any advice on possible tests or solutions for similar problems would be greatly appreciated.
Do you offer Motor Current Signature Analysis (MCSA) services for motors? Is rotor balancing done during motor solo runs with or without a half coupling? We need assistance with high vibration issues on an 11kV Siemens motor. The motor has been overhauled and rewound, but still exhibits excessive vibration at the vertical axis. Despite balance checks, bearing rebuilds, and base corrections, vibration levels remain high. Further tests have been conducted, including a growler test on the rotor and core loss tests on the stator and rotor. However, the vibration persists, with a dominant measurement point at the center of the stator frame. Even after insulation attempts on the bearings, vibration levels remain elevated. Any advice or insights on potential tests or solutions for this issue would be greatly appreciated. Thank you.
Determining the magnetic center of a motor shaft is crucial as it impacts the thrust bearing. A 1500HP motor experienced thrust bearing failure while attempting to reach its magnetic center, which kept shifting. The suspicion was on a potential issue with the stator field, although it could not be proven. Conducting a coast down test with vibration data collection can help differentiate between electrical and mechanical problems. During the test, cutting off power and allowing the motor to coast down while collecting vibration data can provide insights. If the issue disappears, it may be electrical; if it persists, it could be mechanical. Proper thrust position adjustment is also essential. Has anyone encountered similar issues and successfully identified the root cause, whether electrical or mechanical? Utilizing Motor Current Signature Analysis (MCSA) and performing rotor balancing tests can provide additional diagnostic information. Any advice or experiences shared would be greatly appreciated in resolving high vibration concerns in a 11kV Siemens motor.
Greetings Raffie, It is crucial to determine the magnetic center of the rotor. During testing, we noticed that the vibration amplitude does not decrease when turning off the motor; it gradually reduces with the RPM. Despite verifying all mechanical parameters and installing new stator windings, we need to verify the rotor core laminations. We have conducted various tests such as the Growler test, single-phase test, and loop test. We are exploring options to address this issue. When addressing high vibration in an 11kV Siemens motor, it is important to consider the motor shaft's magnetic center, conduct a coast-down test, and analyze vibration data for electrical or mechanical issues. For precise diagnosis, Motor Current Signature Analysis (MCSA) can be a helpful tool. Ensure proper rotor balancing and check for any mechanical faults. Implementing these steps can help in resolving vibration-related problems effectively. Feel free to share your experiences and insights on similar issues for further assistance. Thank you, Vinny Prinu Vincent.
- 05-10-2024
- Gregory Hughes
Hello Vinny, thank you for providing feedback. Based on the coast down test results, it seems like there may be a mechanical issue with the rotor balance. What speed was the rotor balanced at, and was the vibration measured? If the speed was significantly different from the running speed, it's important to extrapolate the vibration data accordingly. I noticed a fan at the end of the motor in the picture - was the rotor balanced along with the fan? It's common for balancing issues to arise from factory elements such as couplings, which may not always be properly balanced. Some components have holes drilled to adjust mass and achieve balance. If possible, please share pictures of the individual elements such as the coupling type, driven load, and the entire shaft when removed from the rotor. Additionally, during the rotor balancing process, were the balance weights securely locked in place? Loose weights can lead to vibration issues. Have we conducted vibration phase checks at the bearing points and legs? Feel free to reach out if you have any more questions. Regards, Raffie Musaib-Ali.
Regarding the 11kV Siemens motor experiencing high vibrations, it's important to consider verifying the rotor core laminations along with the other mechanical parameters checked so far. While the stator windings are new, investigating the rotor core could provide insights. The motor passed tests like the Growler test, Single phase test, and Loop test, but exploring the rotor core lamination integrity remains a priority. Feel free to share any updates on potential solutions or additional tests to address the vibration issue. Vinny Prinu Vincent.
Hello Raffie, The rotor balancing process was conducted at 500RPM G1 standard. We follow the same procedure for similar motors. Initially, the rotor was balanced without the fan, and then balanced again with the fan attached. If possible, could you provide some images of the individual components, such as coupling type, driven load, and the entire shaft when it was removed from the rotor core? The motor underwent testing under solo run or no load conditions, and was received for servicing without the coupling. The shaft remained attached to the rotor core during the process. The balancing weights are securely locked with locknuts to prevent them from coming loose. Cross phase was indeed measured during the procedure. Please let me know if you need any further information. Thank you, Vinny Prinu Vincent.
Original Message Original Message: Sent: 07-18-2023 08:40 From: Raffie Musaib-Ali Subject: 11kV Siemens Motor High Vibration Hi Vinny, thank you for the feedback. From the coast down test results, it seems like there might be a mechanical issue at play. Could you provide details on the speed at which the rotor was balanced and the vibration levels observed? If the speed was significantly different from the running speed, it may be necessary to extrapolate the vibration at running speed. I noticed a fan at the end of the motor in the picture I saw. Was the rotor balanced with the fan attached? Manufacturing issues, such as unbalanced couplings, can contribute to vibration problems. It would be helpful if you could share images of components like the coupling type, driven load, and the entire shaft when it was removed from the rotor. Additionally, ensure that the balance weights were properly secured during the balancing process to avoid any vibration issues. Were vibration phase checks conducted at the bearing points and legs? Your prompt response would be greatly appreciated. Best regards, Raffie Musaib-Ali.
Original Message: Sent: 07-18-2023 08:08 From: Vinny Prinu Vincent Subject: 11kV Siemens Motor High Vibration Hello Raffie, the rotor has been aligned with its magnetic center. Despite thorough testing, the vibration amplitude does not decrease when the motor is de-energized, instead reducing gradually with RPM. All mechanical parameters have been carefully verified, with new stator windings in place. However, we are exploring options to inspect the rotor core laminations for any issues. Important tests have been conducted, including the Growler test, single-phase test, and loop test, all of which the rotor has passed successfully. Thank you for your assistance. Sincerely, Vinny Prinu Vincent.
Edited by Farshid Massumiyan on July 23, 2023 at 08:03 AM. -------------------------
Hello Vinny, we previously experienced a situation where a motor with rotor bar repairs done abroad showed high vibration shortly after installation and testing. Despite attempts to fix the broken rotor bars, the vibration persisted due to budget constraints. Unfortunately, this occurred over 8 years ago, so we do not have the vibration spectrums available.
Vinny, regarding the high vibration in the 11kV siemens Motor you mentioned, we found that the vibration amplitude did not decrease when the motor was de-energized. While the mechanical parameters were checked and the stator windings are new, we suggest verifying the rotor core laminations. Despite passing tests like the Growler test, Single phase test, and Loop test, the rotor might still be the issue.
Have you considered performing a coast-down test with vibration data collection to determine if the problem is electrical or mechanical? This test can help isolate the root cause. If the vibration disappears during coast-down, it could signal an electrical issue, while its persistence suggests a mechanical problem.
Let's work together to identify and solve the vibration issue in the motor. Your insights and expertise would be greatly appreciated. Regards, Raffie Musaib-Ali.
Hello Sundar,
After conducting the MCA, Impendence & CAP tests, we have determined that the parameters are within specifications and well balanced. During the solo run test with Half Key for balancing, everything went smoothly.
Regarding the 11kV Siemens Motor experiencing high vibration, we are equipped to perform MCSA motor current signature analysis. The solo run of the motor was conducted with both half coupling and without coupling for rotor balancing.
Our 11kV 3000 RPM sleeve bearing Siemens motor underwent overhaul and rewinding according to specifications. Unfortunately, during the FAT test/solo run, we detected excessive vertical axis vibration. Despite multiple rotor balances and bearing rebuilds, the vibration persisted. The motor's base exhibited severe softfoot, which we corrected using shims and tested on various bases. Additionally, growler testing on the rotor and core loss tests on the stator and rotor revealed no issues.
Even after trying different approaches such as insulation on bearings and suspension from a crane, the vibration levels remained high. We noticed a rise in 1/2X on the vibration spectrum after June 21st.
If you have encountered similar issues or can suggest further testing possibilities, we would greatly appreciate your insights. Your help in resolving this matter would be invaluable.
Best regards,
Vinny Prinu Vincent
After completing the Motor Current Signature Analysis (MCSA), the rotor was balanced and a test run was conducted with a half key. The motor, a 11kV Siemens Motor, was experiencing high vibration issues, despite being overhauled and rewound to specifications. During testing, vibrations were measured at the vertical axis, showing 1/2X and dominant 1X harmonics. Rotor balancing was meticulously performed multiple times, and bearings were rebuilt to ensure they were within specifications. The motor base had a severe softfoot issue, which was corrected using shims. Various base tests were conducted, and a growler test was done on the rotor with no issues found. Despite using OEM-recommended oil, vibrations were still present, reaching up to 7mm/s. The dominant measurement point was at the center of the stator frame, gradually decreasing towards the bearing housing. Attempting to insulate the bearings did not improve the situation. Suspension of the motor on a crane showed a decrease in vibrations to 4mm/s, but horizontal axis vibrations increased. Seeking advice on further testing or solutions to address these vibration issues.
Hello Vinny, is the motor in question a synchronous or induction motor? If it is synchronous, it is important to ensure that the excitation is functioning properly. Conduct a drop test (watts loss) on the coils to check for any shorted rotor coils, and verify that all pole caps are securely in place. In the past, certain Siemens motors have experienced a rotor pole failure issue known as "Slip Stick," so it's crucial to rule this out. Whether it is an induction or synchronous motor, make sure that the rotor is not magnetized. If it is, degauss the rotor and confirm that the natural harmonic resonance is not a multiple of the running speed. If these steps do not resolve the issue, consider performing a modal analysis of the motor and frame to understand deflection modes during different operating conditions.------------------------------ Victor E Rioli ------------------------------ Original Message Original Message: Sent: 07-16-2023 23:49 From: Vinny Prinu Vincent Subject: 11kV siemens Motor high Vibration Dear members, We are dealing with an 11kV 3000 RPM sleeve bearing Siemens motor that has been overhauled and rewound to specifications. During the FAT test/solo run, we noticed very high vibration along the vertical axis. Vibration levels were measured using an accelerometer, and the spectrum showed 1/2X and harmonics, with 1X being predominant. The rotor has been balanced and checked multiple times, and the bearings have been rebuilt to meet specifications. The motor base exhibited severe soft foot, which we corrected using shims and tested with different bases. Rotor's growler test indicated no issues, and core loss tests on the stator and rotor showed no problems. We used the recommended OEM oil. Despite these measures, we observed high vibrations up to 7mm/s, with the highest levels at the center of the stator frame, gradually reducing towards the bearing housing. The motor originally had no insulation on the bearings, and although we attempted to add insulation on one side, the issue persisted. When the motor was suspended on a crane, vibrations were at 4mm/s, which could also be achieved with foot adjustments, but the horizontal axis vibrations increased. If anyone could suggest additional tests or if you have encountered similar issues, please provide assistance. PLEASE REFER TO THE ABOVE VIBRATION SPECTRUM DETAILS. Until June 21st, only the 1X was visible on the spectrum, but starting from June 23rd, there was an increase in 1/2X. ------------------------------ Vinny Prinu Vincent ------------------------------
Dear Victor, Thank you for your ongoing support. This AC induction motor has presented some challenges, reminiscent of previous issues experienced with a Siemens motor of a similar type. Despite passing all electrical tests, we have concerns about potential core damage, indicated by some blue discoloration on the core. Unfortunately, we lack sufficient evidence to dismantle the core at this point. I will take your suggestion to heart and investigate the natural frequency of the rotor on its own, providing updates accordingly.
Vinny Prinu Vincent
Original Message
Original Message:
Sent: 07-17-2023 11:07
From: Victor E Rioli
Subject: 11kV Siemens Motor high Vibration
Hello Vinny,
Is the motor in question a synchronous or induction type? If synchronous, I recommend checking the excitation, performing a drop test on the coils to detect any shorted rotor coils, and ensuring the security of all pole caps. It is worth noting that certain Siemens motors have been known to experience rotor pole failures, referred to as "Slip Stick." Whether the motor is induction or synchronous, it is crucial to inspect for magnetization of the rotor, degauss if necessary, and verify that the natural harmonic resonance of the rotor does not align with the running speed. If all else fails, conducting a modal analysis of both the motor and frame can provide insights into deflection modes during various operational states.
Victor E Rioli
Original Message:
Sent: 07-16-2023 23:49
From: Vinny Prinu Vincent
Subject: 11kV Siemens Motor high Vibration
Greetings,
We have encountered a significant issue with an 11kV 3000 RPM sleeve bearing Siemens motor, which underwent overhauling and rewinding to meet specifications. During testing, we noticed unusually high vertical axis vibration levels, predominantly showing 1/2X and harmonics on the spectrum, with 1X being the most prominent. Despite repeated balancing of the rotor and rebuilding of bearings, as well as rectifying severe softfoot issues at the motor base, the vibration levels remained elevated. Various tests, including growler tests on the rotor and core loss tests on the stator and rotor, detected no abnormalities. The use of OEM-recommended oil also did not resolve the issue.
Vibration levels, peaking at 7mm/s, were most pronounced at the center of the stator frame, gradually decreasing towards the bearing housing. Even attempts to insulate the bearings did not alleviate the problem, indicating a complex issue at play. Motor suspension tests yielded similar vibration levels, suggesting a consistent issue that persisted despite adjustments. We seek advice on potential tests or solutions to this puzzling vibration problem, as detailed in the spectrum analysis provided.
Vinny Prinu Vincent
Vinny, since the vibration persists even when power is disconnected, electrical issues such as rotor cage faults, stator and rotor core faults, and winding issues can be ruled out. Of utmost importance is the observation that the 1xRPM vibration at 7 mm/sec in the middle of the stator frame is higher than at either bearing. This indicates a localized vibration of the stator frame, likely due to resonance. It is unlikely to be caused by monolithic vibration modes, as higher vibration at the center of a monolithic structure than at the perimeter is uncommon. Conducting an ODS analysis will reveal the localized 1xRPM vibration mode. Optimally, the natural frequency of the rotor should be checked separately to gather more evidence and make an informed decision.
Dear Vincent,
Thank you for your assistance. The AC induction motor in question has similarities to a Siemens motor that exhibited issues in the past. In a previous case, blue coloring on the core suggested core damage, even though it passed all electrical tests. Despite lacking substantial evidence to strip out the core in this instance, I will consider your advice to assess the natural frequency of the rotor independently.
Vinny Prinu Vincent
Victor E Rioli
Vinny, following your feedback and recommendations, it is pertinent to determine if the subject motor is synchronous or induction. For synchronous motors, it is crucial to verify if excitation is functioning correctly and conduct a drop test (watts loss) on the coils to eliminate the possibility of a shorted rotor coil. Moreover, ensure the security of all pole caps to rule out any rotor pole failure phenomenon known as "Slip Stick." In the case of induction or synchronous motors, it is imperative to degauss the rotor if magnetized and ascertain that its natural harmonic resonance is not a multiple of the running speed. If necessary, a modal analysis of both the motor and frame should be performed to identify deflection modes during inrush, running speed, and harmonics.
Victor E Rioli
Vinny, after overhauling and rewinding a 11kV 3000 RPM sleeve bearing Siemens motor, high vibration levels were observed at the vertical axis during the FAT test/solo run. Despite multiple attempts to address the issue, including balancing the rotor, rebuilding bearings, and correcting softfoot with shims, the vibration persisted. The dominant measurement point of the vibration was found to be at the center of the stator frame, gradually decreasing towards the bearing housing. Despite various tests and adjustments, including trying different bases and insulating the bearings, the vibration levels remained high. Seeking advice on possible tests or solutions, as well as experiences with similar issues. Vibration spectrum details show a rise in 1/2X starting from June 23rd.
Vinny Prinu Vincent
- 05-10-2024
- Heather Coleman
Hello Eugene, I appreciate your support. However, before proceeding with ODS and parallelism testing, I would like to explore all other potential causes with the help of a third party. Vinny Prinu Vincent
Original Message: Sent: 07-18-2023 15:28 From: Eugene Vogel Subject: 11kV siemens Motor high Vibration
Vinny, If the vibration persists even when the power is disconnected, it is unlikely to be caused by electrical issues such as rotor cage faults, stator and rotor core faults, or winding issues. The vibration at 1xRPM in the middle of the stator frame may indicate a localized stator frame vibration, potentially due to resonance. An ODS analysis can help identify this vibration mode. Eugene Vogel
Original Message: Sent: 7/18/2023 8:41:00 AM From: Vinny Prinu Vincent Subject: RE: 11kV siemens Motor high Vibration
Hello Victor, Thank you for your assistance. We have encountered similar issues with a siemens motor before, where blue coloring on the core indicated potential core damage despite passing electrical tests. In this case, we do not have enough evidence to strip out the core. I will follow your suggestion to check the natural frequency of the rotor individually and provide an update. Vinny Prinu Vincent
Original Message: Sent: 07-17-2023 11:07 From: Victor E Rioli Subject: 11kV siemens Motor high Vibration
Vinny, To address the high vibration issue with the motor, it is important to determine whether it is synchronous or induction. Perform necessary tests, such as drop tests and excitation verification for a synchronous motor, or check for magnetization and resonance for an induction motor. If all else fails, consider conducting a modal analysis of the motor and frame to identify deflection modes during operation. Victor E Rioli
Original Message: Sent: 07-16-2023 23:49 From: Vinny Prinu Vincent Subject: 11kV siemens Motor high Vibration
Dear members, We have recently observed high vibration levels in our 11kV 3000 RPM siemens motor despite overhaul and rewinding. Various tests have been conducted, including balance checks, rebuild of bearings, and correction of softfoot issues. However, the vibration remains significant, particularly at the center of the stator frame. Further investigations are ongoing, and any insights or similar experiences would be greatly appreciated. Vinny Prinu Vincent
Hello Vinnie, After reviewing all the comments, it seems that you have successfully resolved electrical faults. Now, the focus shifts to identifying whether the issues are related to harmonics, balancing, or sub harmonic vibrations, including rotor dynamic problems like oil whip or air induced whip. Monitoring the phase of vibration during a rundown is crucial as the phase change of 180 degrees at critical speeds can indicate balancing issues. Utilizing technology for a rundown FFT analysis can help pinpoint sub-harmonic frequencies. To tackle the harmonics problem, conducting specific tests to isolate the issue is recommended. One option is to add weight to the bearings to modify the damping force and ensure the rotor runs within the correct range. Adjusting the bearing geometry to prevent issues like oil whip is also crucial. Good luck with resolving these challenges, as troubleshooting such complex problems can be difficult. Malcolm.
Revised Message:
Subject: Siemens Motor High Vibration Issue Resolution Assistance Needed
Dear members,
We have a 11kV 3000 RPM sleeve bearing Siemens motor that has undergone overhaul and rewinding as per specifications. During the FAT test/solo run, we noticed exceptionally high vibration levels on the vertical axis. The vibration was measured using an accelerometer, showing 1/2X and dominant harmonics with 1X. Despite multiple rotor balancing checks and bearing rebuilds, the vibration remains high. We have addressed softfoot issues with shims and tested the motor on various bases, but the problem persists. Additionally, core loss tests and growler tests have revealed no concerns.
The use of OEM-recommended oil and insulation attempts have not alleviated the vibration, which peaks at the center of the stator frame before tapering off towards the bearing housing. Suspending the motor on a crane resulted in 4mm/s vibration, similar to adjustments made on the base, but with an increase in horizontal axis vibration.
We are seeking advice on further tests or solutions for this ongoing vibration issue. Any insights or experiences shared would be greatly appreciated.
Please refer to the vibration spectrum details provided for more information.
Thank you for your assistance.
Vinny Prinu Vincent
If you have a motor connected to a VFD, it is essential to monitor vibration levels during acceleration. If you notice vibration readings between 120K to 160K CPM with harmonics present, consider adjusting the carrier frequency on the VFD to see if there is any improvement. I have observed instances where a misaligned rotor caused high axial and vertical readings, leading to vibrations at half rotation. To address high vibration levels in a Siemens 11kV motor, it is crucial to rule out electrical faults. Potential causes could include harmonics, balancing issues, or rotor dynamic problems like oil whip or air-induced whip. Monitoring vibration phase during a rundown can provide valuable insights, especially when analyzing sub-harmonics. Further testing, such as adding weight to bearings or checking bearing geometry, can help identify and resolve vibration issues. Don't forget to consider factors like the motor's foundation and damping force when troubleshooting vibration problems. Good luck in diagnosing and resolving these complex issues.
Edited on 07-19-2023 at 08:00 by Howard Penrose, 2-pole machines of this size can be challenging to work on. Even minor issues can become apparent. Upon reviewing some responses, it seems beneficial to conduct ESA testing. The MCA description recommends utilizing an ATPro instrument. The ATPOL, employing a variation of the EMPATH software, is capable of conducting no-load testing on the motor.
Given the motor's history of soft foot, likely following a rewind, and evidence of previous repairs, it appears that the frame may be twisted. Another potential issue could be a loose rotor on the shaft, for which there are specific tests available. To assess the rotor bars, options include ESA, vibration testing, or using an analog clamp-on ammeter.
When addressing the persistent vibration, it's advisable to initially inspect the stator or rotor condition as vibrations often indicate some form of looseness. The frequency of half-running speed vibration typically signifies a form of looseness. Vibration checks, such as running speed times rotor bar number and stator slot in acceleration, can help identify potential issues.
Additionally, it's crucial to check for smeared laminations or damage to laminations during rotor bar replacement. Shorted laminations in the rotor could result in bowing during operation, visible as dynamic eccentricity in ESA or vibration testing. Performing a core loss test on the rotor can reveal thermal imbalances, which may be indicated in the localized rotor image.
A few other factors could contribute to the problem, but focusing on rotor bar testing using ESA/MCSA PPF sidebands or rotor vibration tests can help identify issues. When considering the stator, static eccentricity may be a concern, leading to unbalanced magnetic pull (UMP) that should dissipate when the motor is not energized.
Keep in mind that the motor may have multiple defects, often presenting a complex problem. Visit the provided LinkedIn article on ESA testing for further insights on diagnosing motor issues.
Edited by Vinny Prinu Vincent on 07-23-2023 at 08:28 AM Hi Howard, The testing was conducted using the All-Test Pro device. We assessed the CAP, Impedance, Single-phase test, Rotor core loss, Growler, and found no abnormalities. However, it is essential to note that the motor may have multiple defects, which is common in cases of complex issues. I strongly believe that there are several aspects to consider, so we are systematically eliminating all potential causes. I will review the link and provide an update on the outcomes. ------------------------------ Vinny Prinu Vincent ------------------------------
Sent: 07-19-2023 07:50 From: Howard Penrose Subject: 11kV Siemens Motor High Vibration Dealing with 2-pole machines of this size can be challenging. Even minor problems can manifest as high vibration. Based on previous responses, conducting ESA testing would be beneficial. The MCA suggests using the ATPro instrument, which utilizes EMPATH software variations to perform no-load motor testing. Considering the motor's history of soft foot issues, possible rewinds, and repairs, it is likely that the frame is twisted or the rotor may be loose on the shaft. It is crucial to assess the rotor bars using ESA, vibration analysis, or an analog clamp-on ammeter to identify any abnormalities. The ongoing vibration issue, particularly at half-running speed, indicates a potential looseness problem. Vibration checks at different speeds and harmonics can help differentiate between rotor and stator issues. Furthermore, inspecting for smeared laminations and evaluating core loss in the rotor can reveal critical information. While varnishing the rotor is an option, it may hide mechanical flaws until the motor is operational. It is essential to address rotor bar conditions through testing methods like ESA/MCSA PPF sidebands to eliminate potential concerns. Additionally, monitoring for static eccentricity and unbalanced magnetic pull in the stator can provide insight into the motor's condition. Considering the complexity of the problem, it is crucial to address all potential defects systematically. For further information on ESA testing, refer to this LinkedIn article: (6) Detection of No Load Issues with Current Signature Analysis | LinkedIn ------------------------------ Howard W Penrose, Ph.D., CMRP President MotorDoc LLC Lombard, IL
Sent: 07-16-2023 23:49 From: Vinny Prinu Vincent Subject: 11kV Siemens Motor High Vibration Hello everyone, We recently overhauled and rewound an 11kV 3000 RPM sleeve bearing Siemens motor. During testing, we noticed significant vertical axis vibration. Despite our efforts to balance the rotor, rebuild the bearings, and correct soft foot issues, the vibration persisted. Various tests, including Growler and Core loss, revealed no anomalies. The vibration spectrum showed dominant 1X readings at the stator frame's center. We experimented with insulating the bearings, but the issue persisted. Suspension testing showed reduced vibration, but adjustments worsened horizontal axis vibrations. If anyone has encountered similar problems or has testing suggestions, please share your insights. See above for vibration spectrum details. ------------------------------ Vinny Prinu Vincent ------------------------------
- 05-10-2024
- Vanessa Carter
Hello Vinny, I have a few questions for you to consider regarding the 11kV Siemens motor with high vibrations. Firstly, why was the motor sent for repair? Were there similar issues experienced before? Secondly, is the lubricating oil temperature adequate? Thirdly, have you verified the stability and consistency of the phase readings? Fourthly, does the rotor coast down properly when the motor is shut down, or are there signs of increased friction? Lastly, were there any indications of uneven wear across the bearing pad during the inspection of the bearings? Your input on these questions would be greatly appreciated. Thank you. ------------------------------ Christopher Spoor ------------------------------
Keywords: 11kV Siemens motor, high vibrations, lubricating oil temperature, phase readings, rotor coast down, uneven wear, bearing pad, motor repair, motor maintenance, vibration spectrum, motor inspection, motor troubleshooting, motor vibration issues.
Vinny, can you please clarify the 1x magnitude when the motor reached 1500 rpm during coastdown? If the issue is due to unbalance, the magnitude at 1500 rpm should be a quarter of the 1x at 3000 rpm. If you are experiencing a rigid body mode at operating speed, the magnitude at 1500 rpm will be minimal. Additionally, you can determine if it's the first or second rigid body mode based on the phase: verticals in phase for the first mode and 180 degrees out of phase for the second mode.
Regarding the high vibration issue with the 11kV Siemens motor, the motor has been overhauled and rewound according to specifications. Despite multiple checks and adjustments, high vibrations at the vertical axis persist, with 1/2X and harmonics present in the spectrum analysis. Various tests have been conducted, including balancing the rotor, rebuilding bearings, addressing softfoot issues, and using recommended oil. However, vibrations up to 7mm/s are still present, with the center of the stator frame showing the highest measurement point. Even with insulation attempts and suspension of the motor, vibrations remain a challenge.
If you have any insights or similar experiences to share, please advise on possible tests or solutions for this ongoing vibration issue. The vibration spectrum details provided indicate a rise in 1/2X from June 23 onwards. Your expertise and guidance would be greatly appreciated.
Sincerely,
Vinny Prinu Vincent
Vinny, I understand you are a repair shop working on a customer's motor. Can you please provide more images of the rotor before it is varnished or painted? The image you shared of the rotor shows signs of overheating, indicated by blue/purple discoloration on the rotor bars. Upon analyzing the vibration data you provided, I noticed pole pass sidebands at multiples of the running speed (1x, 2x, 3x, 4x, 5x, 6x). Could you supply vibration data using the following parameters: 30000 cpm/500hz fmax, 12800 lines of resolution, 2 averages, 50% overlap, hanning window, for both ends of the motor in horizontal, vertical, and axial directions? There are still many details missing, but I am curious about how the motor's vibration pattern changes so rapidly. Excessive starting and stopping can lead to rotor stress and eventual failure. Did a specific component fail, or did the motor suddenly start vibrating? Is there a growling or modulating noise when the motor runs? I assume the two-phase pictures depict the top image as horizontal and the bottom image as vertical. How is it possible for a motor of this size and mass to be 180 degrees out of phase in any direction? Have you measured the air gap between the rotor and stator at different locations? Have you gathered vibration data on your test stand's base, specifically at the motor feet for phase data? Is the motor actually out of phase, or is it the test stand that is moving? Have you performed a running soft foot check? While the motor is running, try loosening one or two motor foot bolts to see if there is a change in vibration. Soft foot issues can lead to high vibration levels, even if you believe you have addressed them. Are there shims between the motor feet and the test stand? Do the shims cover the entire surface area of the motor foot? Dave ------------------------------ Dave Reynolds www.midlandsrc.com ------------------------------ Original Message Original Message: Sent: 07-16-2023 23:49 From: Vinny Prinu Vincent Subject: 11kV siemens Motor high Vibration Hello members, We recently worked on an 11kV 3000 RPM sleeve bearing Siemens motor that was overhauled and rewound as per specifications. During the FAT test/solo run, we noticed unusually high vibration along the vertical axis. Vibration measurements using an accelerometer indicated 1/2X and harmonics, with 1X being the dominant frequency. Despite multiple checks and balances on the rotor and bearings, including rebuilding and confirming specifications, the vibration persisted. We identified a severe soft foot issue at the motor base, which we corrected with shims and tested on various bases. Additional tests on the rotor and stator, such as growler and core loss tests, showed no anomalies. We used the OEM-recommended oil, but the vibration levels remained high, reaching up to 7mm/s. The point of dominant vibration was at the center of the stator frame, decreasing towards the bearing housing. Even after insulating one side of the bearings, the vibration worsened. Suspending the motor on a crane showed a decrease in vibration (4mm/s), which could also be achieved with adjustments on the motor's feet, albeit with an increase in horizontal axis vibration. If anyone has encountered similar issues or can suggest additional tests, please offer your insights. PLEASE SEE ABOVE FOR VIBRATION SPECTRUM DETAILS. Until June 21st, we only observed 1X on the spectrum, but from June 23rd, there was a rise in 1/2X. ------------------------------ Vinny Prinu Vincent ------------------------------
Hello, Dave mentioned an issue with shims being stacked to make up a certain thickness. To address this, we now use a combination of thick and thin shims to ensure proper alignment. It's important to consider the impact of soft foot checks on frame distortion. Regards, Raffie.
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Subject: Siemens Motor Vibration Analysis and Testing
Vinny, it appears that you are repairing a customer's motor. Could you provide additional images of the rotor pre-varnish/paint? The rotor shows signs of overheating, indicated by blue/purple discoloration on the bars. The vibration data suggests sidebands around multiples of the running speed. Please provide vibration data with specific parameters for a more detailed analysis. Consider factors like starts/stops and soft foot issues that may impact the motor's vibration pattern. Check for growling or modulating noises during operation as well.
Have you checked the air gap between the rotor and stator at multiple points? Conduct vibration tests on the motor feet and test stand base to identify any issues. A running soft foot check could reveal hidden problems causing high vibration levels. Ensure proper alignment with shims and verify if the motor or test stand is causing phase discrepancies.
Your diligent testing and analysis will help pinpoint the root cause of the motor's high vibration levels. Share any updates or concerns for further assistance. Thank you.
Dave Reynolds
www.midlandsrc.com
- 05-10-2024
- Rebecca Murphy
Updated by Farshid Massumiyan on July 23, 2023 at 8:00 AM.
- 05-10-2024
- Wesley Jenkins
Hello, last year, we encountered a similar issue with an 11kV Siemens motor exhibiting high vibration levels during testing. Despite multiple attempts at troubleshooting and seeking help from other workshops, the problem persisted until we decided to install the motor on-site. Surprisingly, the motor operated perfectly with acceptable vibration levels after running for two days. We tried balancing the rotor, cooling fan, and coupling separately, but we believe the difference was in the heavily cemented base compared to our iron base. The motor was tested with various bases, and adjustments were made to correct softfoot issues. However, the dominant vibration point remained at the center of the stator frame. If you have experienced similar issues or have suggestions for further testing, please share your insights. Thank you.
Hello Din,
Your recent experience contrasts with a situation I faced years ago. My team reported a motor with electrical faults and imbalance issues regularly while in the plant. Despite multiple removals and tests, no electrical test methods were available at the time. After witnessing a successful motor run-up on the machine shop floor, we re-installed it in the plant, only to find high vibrations post-installation. Suspecting a rotor issue, we checked the vibration phase and confirmed it was running above a critical speed while on its concrete base. To address this, we used sandbags to prove a stiffness issue due to the inadequate weight of the concrete plinth. This temporary solution led us to increase the size of the concrete base, resolving the problem permanently. The science behind vibration management involves considering the rotor's mass, stiffness, and damping from bearings and base plates. Most electrical motor rotors are designed to run above their first critical speed, which is considered the self-balancing region. If the base and bearings lack stiffness, the rotor may run above the second critical speed, resulting in high vibrations. In such cases, balancing at high speed is necessary to address flexing issues. Adjusting support stiffness or using electromagnetic bearings to alter stiffness at specific speeds can prevent high vibrations during operation.
I hope this explanation clarifies the phenomenon for you. For further details, you can refer to articles on Vibration and Rotordynamics on Wikipedia.
Best regards,
Malcolm Hide
Are you experiencing high vibration levels at the center of the stator frame and lower levels at the bearing housings in your 11kV Siemens Motor, similar to what Vinny reported? This unusual condition may indicate resonance in the stator frame. It's essential to address this issue promptly to prevent further damage and ensure optimal performance. The vibration spectrum details provided can offer valuable insights into potential causes and solutions. If you have encountered similar issues or have suggestions for possible tests, please share your expertise to help resolve this issue effectively. Your input is greatly appreciated.
Hello Eugene, I believe the bearings' side was measured during the in-situ balancing process. Initially, the vibration values were acceptable during the test bench balancing, but they increased with temperature. To address this, we added over 600 grams of balancing mass on each side. In retrospect, it would have been beneficial to mark and retain the original weights on the rotor before conducting the initial balancing procedure.
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Din Ellias
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Original Message
Sent: 07-26-2023 07:40
From: Eugene Vogel
Subject: 11kV Siemens Motor Experiencing High Vibration
Din, it seems you encountered a similar issue before. Vinny's report states: "High vibration up to 7mm/s was detected, with the most significant readings at the center of the stator frame, gradually decreasing towards the bearing housing." Did you also experience high vibration at the stator frame's center and lower levels at the bearing housings? This is an uncommon issue, possibly indicating resonance within the stator frame.
Eugene Vogel
Hello Din, the issue with Vinny's motor is quite peculiar. The vibration amplitude at 1xRPM is significantly higher at the center of the stator frame than at the bearings. This suggests a resonance condition, indicating that the stator frame itself may be distorting at that specific frequency. This phenomenon points to a resonance condition within the stator frame, which is impacting the overall vibration levels. Gene
Good morning experts, I was preoccupied with resolving an issue and made some progress. We installed a counterweight plate on the NDE side of the cooling fan seat and adjusted the trim balance to monitor any changes. As a result, vibration levels decreased to 2.5mm/s at the DE vertical axis and were below 1mm/s on all other axes. However, the stator frame vibration remained at 3.5mm/s. Interestingly, adjusting the base bolts either loosened or tightened caused an increase in vibration values. Additionally, transferring weights from the plate to the rotor yielded varied results depending on the unit's installation at the plant. It may be necessary to repair any twists in the core and windings for optimal performance. If experiencing a similar issue or have advice on possible tests, please provide assistance. Thank you.
Vinny Prinu Vincent