Archive | Motors & Drives

11

9:00 am
July 18, 2016
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Interchangeable Coupling Line

1607mtprod21pThe company’s line of L-Jaw couplings includes a range of bore sizes and aluminum and stainless-steel hubs. The line is part-for-part interchangeable with industry-standard designs. An interchange guide is available. A wide range of sizes is offered with torque ratings to 6,228 in. lb. and bore sizes to 2 7/8-in. dia. Couplings can accommodate as much as 1 in. of angular misalignment and have an operating temperature range of –60 to 250 F.
TB Wood’s Inc.
Chambersburg, PA
tbwoods.com

7

9:00 am
July 13, 2016
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Hybrid Drives

PowerPoint PresentationU.S. Motors-brand Hybrid Drives are part of the Accu-Series line of 1- to 10-hp drives. The off-the-shelf, digital AC drives are said to require no programming or commissioning, install easily, and be up and running in 10 min. Drives are available as IP20, NEMA 1/IP20 & 50, and NEMA 4X/IP65. Custom applications are available.

Nidec Motor Corp. (NMC)
St. Louis
nidec-motor.com

275

11:55 am
June 28, 2016
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My Motor Failed. Now What?

 By Screen Shot 2016-05-16 at 11.53.51 AMMike Howell, Electrical Apparatus Service Association (EASA)

PROCESS DOWNTIME is expensive—even more so when it’s unexpected. So, when an electric motor fails, we tend to pull, repair, or replace it, and move on as quickly as possible. In doing so, however, we may miss an opportunity to capture basic information that could help improve the reliability of the application. With a little planning, these data can be gathered with no delay in startup.

Collect initial data. Develop a simple, standard procedure that a “trained” operator can use to jot down or check off some basic information about the process at the time of failure. In special applications or cases of chronic failure, photos could be extremely helpful.

Don’t destroy two motors. Startup procedures vary widely, depending on factors such as application and equipment size. Have appropriate measures in place so that, following a failure, you can rule out problems with the power supply or starting equipment before attempting to start a replacement motor.

This sleeve bearing motor, with a drive-end bearing failure and bent shaft, arrived at a service center without its sheave, and with very little information. Bearing wear was presumed to be the cause of failure. After the motor was returned to service with a new shaft and new sleeve bearings, it failed in less than an hour. A simple photo of the motor following the initial failure would have correctly identified the cause—excessive overhung load for the sleeve bearing—and a motor with rolling-element bearings could have been installed to prevent a second failure.

This sleeve bearing motor, with a drive-end bearing failure and bent shaft, arrived at a service center without its sheave, and with very little information. Bearing wear was presumed to be the cause of failure. After the motor was returned to service with a new shaft and new sleeve bearings, it failed in less than an hour. A simple photo of the motor following the initial failure would have correctly identified the cause—excessive overhung load for the sleeve bearing—and a motor with rolling-element bearings could have been installed to prevent a second failure.

Help your service center. Sometimes, the cause of failure seems so obvious that, with too little information, we jump to the wrong conclusion. Furthermore, we may only discover our error when the repaired motor or its replacement quickly fails. The more application and failure details that you can share with service-center personnel, the easier it will be for them to help identify and eliminate the actual problem and provide a reliable repair for the application. With most applications, much of the documentation can be done long before a failure occurs. Such details can make all the difference when the service center performs causal analysis. Examples of data that can be recorded in advance include:

  • Complete motor nameplate information
  • Power supply information: sinewave/non-sinewave power (ASD/VFD), known transients, voltage variation, voltage unbalance, starting method
  • Environment: indoors/outdoors, ambient temperature, humidity, contamination
  • Mounting and coupling: direct coupled, belt drive, integral mounted, overhung load, mounted vertically
  • Application information: pump, blower, conveyor, crusher, inertia/starting torque requirements, acceleration time, duty cycle, typical loading.

Once a failure occurs, combine this general information about the application with specifics about the failure event, including any available photos. This approach will get your service center off to a good start in accurately determining the cause of your motor’s failure and preventing another one. MT

Mike Howell is a technical support specialist at the Electrical Apparatus Service Association (EASA), St. Louis. For more information, visit www.easa.com.

141

4:16 pm
May 16, 2016
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Avoid Costly Motor Connection Mistakes

By Mike Howell, Electrical Apparatus Service Association (EASA)

Manufacturers deploy various external connection schemes to produce three-phase induction motors for multiple voltages and/or starting methods. Be sure to follow the relevant connection diagram, which is usually affixed to the motor or contained in its manual. If the diagram is lost, damaged, or ignored, you could find yourself dealing with a costly rewind.

The following tips apply to connections commonly encountered on machines with one speed at power frequency. If the external connection information isn’t available, ask your local service center for assistance, especially if several lead tags are missing or there are multiple nameplate speed ratings at power frequency. The service center can also help with unconventional numbering or cross-referencing IEC and NEMA numbering. Caution: The integrity of lead markings is only as good as the electrician who removed the motor from service and quality of the labeling materials at hand.

3 Leads

While three-lead connections are the most straightforward, always check the direction of rotation before finalizing the motor installation, regardless of the lead quantity.

6 Leads

If leads are numbered 1 to 6, the winding can usually be connected wye or delta. On machines rated for two voltages, the wye connection is for the high voltage; the delta connection is for the low voltage.

For a single voltage rating, most six-lead machines are capable of wye-delta starting (and will run in delta). The exception would be some large machines that have external wye connections to facilitate differential protection.

If leads are numbered 1 to 3 and 7 to 9, the winding is capable of part-winding start. When using a different starting method, e.g., soft start, variable-frequency drive, or across-the-line, always connect the machine for run.

Some machines will have 1-1, 2-2, 3-3, indicating a delta-run motor. Also, since some part-winding start motors are numbered incorrectly as 1 to 6, remember the starting method you’re using.

9 Leads

If leads are numbered 1 to 9, the motor is typically rated for two voltages and could be designed with either a wye or delta connection. Using the machine on the higher rating, the external connection is the same either way.

Screen Shot 2016-05-16 at 11.10.39 AM

On the lower voltage rating, though, the external connection will be different for wye- and delta-connected units. Verify what you have! If a multimeter shows continuity between leads 7, 8, and 9, the machine is wye-connected (see Fig. 1).

12 Leads

If leads are numbered 1 to 12, the motor is typically rated for two voltages and could be used with a wye-delta starter at either voltage, or a part-winding starter for low voltage only. Units rated for single voltage may have 12 leads and be suitable for wye-delta or part-winding starts. Twelve-lead induction motors will almost always run connected delta.

Unmarked Leads

If only a couple of leads are unmarked, you may be able to restore numbering by process of elimination. Otherwise, it’s best to ask a service center for assistance, because they have reliable procedures for identifying leads.

Screen Shot 2016-05-16 at 11.10.51 AM

Uncoupled Run

If there’s any doubt about the external connection, it’s a good idea to run the machine unloaded to determine the direction of rotation and no-load current. A no-load current significantly above or below the ranges in Table I may indicate a connection error, or a winding error on rewound motors. (Caution: Never operate a roller-bearing machine without radial load.) MT

Mike Howell is a technical support specialist at the Electrical Apparatus Service Association (EASA), St. Louis. For more information, visit www.easa.com.

393

5:49 pm
April 11, 2016
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Motor-Testing Tools Expand Services

Ken Patterson, head of the predictive-maintenance division at Koontz-Wagner, tests a 9,000-hp motor.

Ken Patterson, head of the predictive-maintenance division at Koontz-Wagner, tests a 9,000-hp motor.

New state-of-the-art instruments at Midwest service-provider Koontz-Wagner helped boost the company’s profits by 10%.

Growing companies typically make investments in state-of-the-art tools and equipment so that they may expand their ability to serve their customers. One such company, Koontz-Wagner Services, South Bend, IN, has capitalized on several opportunities since acquiring new energized and de-energized motor-testing equipment.

Koontz-Wagner Services is a leading Midwest provider of repair and maintenance services for rotating-equipment systems, including electric motors, generators, and mechanical power-transmission components, along with electrical-contracting services that range from short-order services to design and complex large-project services.

Kenneth L. Patterson, Koontz-Wagner’s proactive predictive-maintenance (PdM) manager, led the effort to obtain sophisticated motor-testing equipment for the company. In January 2015, after having conducted extensive research on different types of technologies, he turned to products from All-Test Pro, Old Saybrook, CT.

Patterson chose two hand-held, de-energized motor testers: the All-Test Pro 5 and All-Test Pro 31, in addition to the All-Test Pro On-Line II energized motor tester. His 12-person PdM team participated in a standard post-sale training session conducted by All-Test Pro. The team was thoroughly educated on how to perform advanced non-destructive motor testing and analysis for de-energized motor-circuit analysis and energized electrical-signature and power analysis.

Testing motors

As a full-service company, Koontz-Wagner has motor-repair, predictive-maintenance, and construction divisions. Its motor-repair division made immediate use of the de-energized motor-testing equipment by streamlining its inspection processes.

“Using the AT5 and the AT31 has helped us reduce the time it takes to understand the general condition of a motor,” explained Patterson. “The AT5 motor-circuit analyzer shows us if there are bad connections or ground faults, it checks the winding, and it lets us know if there are air gaps, contamination, or broken bars. It gives us a pretty good picture of the motor’s health within just a few minutes; which is important because reducing the time it takes us to inspect a motor has enabled us to lower the cost of that initial inspection,” he continued. “The incoming inspection fees we had been charging customers were a little high, compared with our competitors, so changing our inspection process has allowed us to lower those initial inspection fees and become more competitive.”   

Koontz-Wagner service technician Erik Lehman uses the All-Test Pro 5 to perform initial inspection of a 50-hp motor in his company’s repair shop.

Koontz-Wagner service technician Erik Lehman uses the All-Test Pro 5 to perform initial inspection of a 50-hp motor in his company’s repair shop.

Increasing business opportunities

In September of 2015, Koontz-Wagner’s maintenance-services organization began using its portable de-energized motor-testing equipment outside of the repair shop. A long-time relationship with a large automotive-supply company presented the service providers with an opportunity to offer additional value-added support. The automotive supplier maintains an inventory of approximately 700 spare motors.

Over the course of three months, Koontz-Wagner’s PdM technicians went through this inventory to check the health and condition of all spare units. “Out of that inventory of about 700 motors, we found that about 100 required maintenance,” explained Patterson. “We used the AT5 on-site, which was great because it generates reports quickly, so it was ideal for that particular project. Now, we are scheduling these motors to come into our motor-repair division for service.”

Revenue from energized testing

Energized testing has become another area of sales growth for Koontz-Wagner. “I have generated quite a bit of income using the All-Safe Pro,” Patterson noted. The product is an adaptor installed inside the electrical cabinet that works with the ATPOL II energized testing instrument. This adaptor provides the necessary signals to help preventive-maintenance professionals understand the condition of operating motors with minimal risk and without bulky, protective gear.

Koontz-Wagner’s construction-division team of electricians has installed 15 All-Safe Pro adaptors inside various customer electrical cabinets. Then its predictive-maintenance team members use the All-Test Pro On-Line II energized tester to obtain data on operating motors and further support their customers’ condition-based monitoring and PdM programs.

As an example, Patterson pointed to having performed vibration testing on a compressor motor for a customer and the fact that the ATPOL II confirmed the results. “Maintaining the health of a 200-hp compressor motor,” he said, “is critical because the unit provides air to this automotive customer’s facility.”

According to Patterson, All-Test Pro’s technologies are helping his company in many ways, so much so that he’s hoping to expand Koontz-Wagner’s capabilities even more in 2016 using these instruments. No wonder: The company credits the new motor-testing equipment with helping increase its profits by 10%, proving that there are real benefits to investing in modern tools and technology. MT

For more information on these motor-testing tools and other All-Test Pro technologies, visit alltestpro.com.

169

5:17 pm
March 18, 2016
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Prevent Motor Bearing Failures

Understanding the top five causes of failed motor bearings will help stop these problems in their tracks.

According to the bearing experts at SKF (Gothenburg, Sweden, and Lansdale, PA) these five damage mechanisms are the most common causes of motor-bearing failures. Understanding them as you examine a failed bearing can help you prevent their recurrence.

Electrical erosion
Electric erosion (arcing) can occur when a current passes from one ring to the other through the rolling elements of a bearing. While the extent of the damage depends on the amount of energy and its duration, the result is usually the same: pitting damage to the rolling elements and raceways, rapid degradation of the lubricant, and premature bearing failure. To prevent damage from electric-current passage, an electrically insulated bearing at the non-drive end is usually installed.

Inadequate lubrication and contamination
If the lubricant film between a bearing’s rolling elements and raceways is too thin, due to inadequate viscosity or contamination, metal-to-metal contact occurs. Check first whether the appropriate lubricant is being used and that re-greasing intervals and quantity are sufficient for the application. If the lubricant contains contaminants, check the seals to determine whether they should be replaced or upgraded. In some cases, depending on the application, a lubricant with a higher viscosity may be needed to increase the oil-film thickness.

Damage from vibration
Motors transported without the rotor shaft held securely in place can be subjected to vibrations within the bearing clearance that could damage these components. Similarly, if a motor is at a standstill and subjected to external vibrations over a period of time, its bearings can also be damaged. To prevent these problems, secure the bearings during transport in the following manner: Lock the shaft axially using a flat steel bent in a U-shape, while carefully preloading the ball bearing at the non-drive end. Then radially lock the bearing at the drive end with a strap. In case of prolonged periods of standstill, turn the shaft from time to time.

Damage caused by improper installation and set-up
Common mistakes in installation include using a hammer or similar tool to mount a coupling half or belt pulley onto a shaft; misalignment; imbalance; excessive belt tension; and incorrect mounting resulting in overloading. To prevent these problems, use precision instruments such as shaft-alignment tools and vibration analyzers and other appropriate tools and methods when mounting bearings.

Insufficient bearing load
Bearings always need to have a minimum load to function well. If they don’t, damage will appear as smearing on the rolling elements and raceways. To prevent these problems, be sure to apply a sufficiently large external load to the bearings. This is crucial with cylindrical roller bearings, since they are typically used to accommodate heavier loads. (This, however, does not apply to preloaded bearings.) MT

SKF is s a global supplier of bearings, seals, mechatronics, lubrication systems, and services that include technical support, maintenance and reliability services, and engineering consulting and training. For more information on motor bearings and other technologies and topics, visit skf.com.

214

4:50 pm
February 24, 2016
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Prevent Motor-Bearing Failures

Learn the latest on the top five causes of failed motor bearings to help stop these problems in their tracks.

By examining a failed motor bearing and understanding the clues that various types of damage often produce, you can keep these problems from plaguing your motor fleet in the future.

By examining a failed motor bearing and understanding the clues that various types of damage often produce, you can keep these problems from plaguing your motor fleet in the future.


According to the bearing experts at SKF (Gothenburg, Sweden, and Lansdale, PA) these five damage mechanisms are the most common causes of motor-bearing failures. Understanding them as you examine a failed bearing can help you prevent their recurrence.

Electrical erosion
Electric erosion (arcing) can occur when a current passes from one ring to the other through the rolling elements of a bearing. While the extent of the damage depends on the amount of energy and its duration, the result is usually the same: pitting damage to the rolling elements and raceways, rapid degradation of the lubricant, and premature bearing failure. To prevent damage from electric-current passage, an electrically insulated bearing at the non-drive end is usually installed.

Inadequate lubrication and contamination
If the lubricant film between a bearing’s rolling elements and raceways is too thin due to inadequate viscosity or contamination, metal-to-metal contact occurs. Check first whether the appropriate lubricant is being used and that re-greasing intervals and quantity are sufficient for the application. If the lubricant contains contaminants, check the seals to determine whether they should be replaced or upgraded. In some cases, depending on the application, a lubricant with a higher viscosity may be needed to increase the oil-film thickness.

Damage from vibration
Motors transported without the rotor shaft held securely in place can be subjected to vibrations within the bearing clearance that could damage these components. Similarly, if a motor is at a standstill and subjected to external vibrations over a period of time, its bearings can also be damaged. To prevent these problems, secure the bearings during transport in the following manner: Lock the shaft axially using a flat steel bent in a U-shape, while carefully preloading the ball bearing at the non-drive end. Then radially lock the bearing at the drive end with a strap. In case of prolonged periods of standstill, turn the shaft from time to time.

Damage caused by improper installation and set-up
Common mistakes in installation include using a hammer or similar tool to mount a coupling half or belt pulley onto a shaft; misalignment; imbalance; excessive belt tension; and incorrect mounting resulting in overloading. To prevent these problems, use precision instruments such as shaft-alignment tools and vibration analyzers and other appropriate tools and methods when mounting bearings.

Insufficient bearing load Bearings always need to have a minimum load to function well. If they don’t, damage will appear as smearing on the rolling elements and raceways. To prevent these problems, be sure to apply a sufficiently large external load to the bearings. This is crucial with cylindrical roller bearings, since they are typically used to accommodate heavier loads. (This, however, does not apply to preloaded bearings.)

Source
SKF is s a global supplier of bearings, seals, mechatronics, lubrication systems, and services that include technical support, maintenance and reliability services, and engineering consulting and training. For more information on motor bearings and other technologies and topics, visit skf.com.

621

10:05 pm
February 8, 2016
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Select the Best VFD for Your Application

Choosing the right variable frequency drive for an application involves several important considerations. For example, based on acceleration requirements, sensorless vector control may be more suitable than volts-per-hertz (V/f) control. While V/f control is effective in dragging logs up a slope, it’s not appropriate for dockside hoists that position 12-ton shipping containers to within inches.

Choosing the right variable frequency drive for an application involves several important considerations. For example, based on acceleration requirements, sensorless vector control may be more suitable than volts-per-hertz (V/f) control. While V/f control is effective in dragging logs up a slope, it’s not appropriate for dockside hoists that position 12-ton shipping containers to within inches.

According to the technical experts at Mitsubishi Electric Automation, Vernon Hills, IL, there are several factors to consider when selecting variable-frequency drives (VFDs). Among them:

What is your load type: constant or variable torque?

For a constant-torque load, the torque is independent of speed (ignoring momentary shock loads). Examples include conveyors and hoists. For a variable-torque load, torque varies as a function of speed. Examples include fans and pumps. This primary distinction underlies every decision you’ll make about the type of drive.

What are your acceleration requirements?

Does it matter how fast your load accelerates up to speed? For a fan, probably not. For a centrifuge, almost certainly. In the latter case, you may want to select sensorless vector control, rather than volts-per-hertz (V/f) control. While the V/f approach is effective for many applications, it doesn’t allow a motor to develop near-full torque at near-zero speeds (unlike sensorless vector control). V/f control can be appropriate for dragging logs up a slope, but not for a dockside hoist that needs to position a 12-ton shipping container to within inches.

Controlled deceleration presents its own challenges.

During decelerations, the motor acts as a generator. The resulting energy needs to go somewhere, and is typically dissipated as heat in a braking resistor. Controlled-deceleration capability is a good solution for constant-torque loads, changing loads, or even unbalanced loads.

What is your speed range?

Although a conveyor belt may operate consistently at 60 Hz, for an unspooling module on a printing line, the motor needs to deliver torque as effectively at 0.5 Hz as 60 Hz. This is another application where garden-variety V/f control won’t do the job. Sensorless vector control will (and most VFDs these days include it). Keep in mind, however, that not all offerings are created equal. Be sure to double check specifications against your requirements.

Do you need to optimize energy usage?

Instead of wasting all of the energy harvested when your motor is overhauling, you can apply it to your next move, courtesy of a regenerative VFD. These drives have internal capacitors that temporarily store energy for reuse.

Do you need an encoder?

Not all drives are the same at low speeds. A drive with a 200-to-1 speed range, for example, can provide 100% speed from your motor down to about 1/3 Hz. This might be acceptable for some applications, but not others—in which case you’ll need an encoder, Since not all drives work with encoders, you’ll want to determine your need for this capability in advance. MT

VFD Sizing Matters

Back in the day, an undersized drive—a common situation in plants—would simply trip when it exceeded operating specifications. Today, VFDs are very good at limiting themselves so they don’t trip.

The bad news? While a properly sized drive today might allow the system to complete acceleration in one second, as commanded, one that’s too small for a task will take two or three seconds. In short, an undersized drive will compensate, but the system won’t perform as desired and the compensation could mask the true problem.

Mitsubishi Electric’s technical experts also note that it’s crucial to size a drive based on peak current command—not on horsepower. Because of horsepower’s connection to motor size, it’s easy to focus on it. In reality, though, you want to size a drive so that the maximum current in the worst-case scenario is always within the mode of the unit’s continuous-current rating.

For more information on selecting VFDs, including various design, installation, and operational factors, visit us.mitsubishielectric.com/fa/en.

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