Frequently Asked Questions
Power Services
Infrared Scans
How often do I need Infrared Scanning?
Does my equipment need to be running for an infrared scan?
When making a bolted electrical connection, is a tighter
connection more advantageous?
Do I need to open the doors on the motor control centers?
Do you have the proper NFPA 70E equipment?
Switchgear
How often do I need to inspect my switchgear?
How often should we test our switchgear (breakers, protective relays, transformers etc)?
Transformers
How often do I need to perform oil sampling?
Miscellaneous Power Service
Why is maintenance important? It's working now so why
should I mess with it?
What if it's too hard to take the equipment offline to test?
How much of a problem are harmonics, and how do you isolate them?
Why does it matter what ratio the multi-ratio CT is tapped at?
What advantages are there to upgrading protective relays to newer, microprocessor based units?
What are DGA monitoring systems?
How long will it take for testing to be completed?
Have you ran into this issue on this type of equipment before?
Reliability Services
General Reliability Topics
How long does a typical balance and alignment job take?
What do I need to be concerned with regarding my DC motor?
Should I go in-house with our Vibration Analysis Program?
How often should I have vibration readings taken on our equipment?
How can I assess the health of bearings out of physical reach?
Do you provide any permanently mounted vibration analysis hardware that provides alarms?
How often should I perform VAP service?
Rotating Apparatus Repair Services
General Repair Questions
What is your lead time for repair jobs?
If I have a "hot" job, what would you do to limit my down time?
How often should I grease my motors?
How much grease do I use to grease my motor?
Should I be concerned with greasing my motors too much?
At what HP range do I repair my motor instead of replacing it?
Can I still purchase the old Reliance motor
that I have used for many years?
Are medium voltage motors covered by Energy
Independence and Security Act (EISA)?
Will a repaired or rebuilt high-efficiency motor
retain their original efficiency?
What horsepower does it pay to start rewinding a motor?
Does your repair shop have a schedule for calibrating their testing equipment & measuring tools?
The model number of my motor ends with a letter. What does that represent? (Wxample 284tcz)
How does my high-efficiency motor being affect belt drive applications?
Why, when looking at purchasing a spare 4 Kv fan motor is the Wk2 so important?
General Questions
Can we send in a electronic purchase order?
What are your specific location addresses
for mailing orders, requests, and shipping repairs?
Where can I find motor and drive data for equipment
I have bought from L&S?
How often do I need Infrared Scanning?
Infrared scanning needs to be conducted every twelve months. You may need to do monthly scans on critical applications.
Does my equipment need to be running for an infrared scan?
Yes. To get the best results you need to have as much equipment running as possible and under load for the best results.
When I receive my annual Infrared Survey report, what approach should I be taking to remedy the problem areas?
In many cases the maintenance supervisor hands off the report to the electrician who assumes that all of the problem areas identified in the infrared report can be remedied by just tightening the connection. To properly address each problem area the connection should be broken, cleaned and retightened to the recommended amount of torque specified by the connector manufacturer. If this information is not available the maintenance person needs to use good judgment and not over tighten the connector.
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When making a bolted electrical connection, is a tighter connection more advantageous?
Not necessarily. Electrical maintenance personnel often over-tighten connections. They assume it's the best practice concerning electrical connections. In order to achieve maximum conductivity between two conductors, there must be as much contact between mating surfaces as possible. When connectors are over-tightened, they often become distorted reducing the amount of surface area between the connector and conductor, thereby reducing the overall effectiveness of the connection. Infrared scans can be used to locate and evaluate these bad connections.
What do we do if our insurance company handles the company we contract for I/R testing? They contract someone who handles all of our plants across the country.
They typically come in once every year or two. What happens if something occurs in the meantime? It's a good idea to have local source as a backup. We often come in as a backup for a second test and to handle any issues that may come up. Furthermore, we also inspect, clean, and test all your electrical switchgear.
Do I need to open the doors on the motor control centers?
Yes. Looking at the connections inside the buckets allows us to determine the exact cause of the problem.
Do you have the proper NFPA 70E equipment?
Yes. Our uniforms are NFPA 70E compliant. We also have gloves, hard hats, face shields, and additional attire for the higher arc flash ratings.
How often do I need to inspect my switchgear?
You should conduct a visual inspection every month.Each year you should do a visual and mechanical inspection.You need to do a visual, mechanical, and electrical inspection every three to five years.
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How often should we test our switchgear (breakers, protective relays, transformers etc)?
We recommend a three year rotation, meeting the requirement of most insurance companies.
How often do I need to perform oil sampling?
Transformer oil analysis need to be performed every 12 months. It's important to develop a habit to consistently monitor the condition of the transformer. This creates a sample history that allows analysis over time. The samples should also be sent to the same lab as well, to keep consistency.
Why is maintenance important? It's working
now so why should I mess with it?
If we find an issue, it can be isolated and planned for. If your equipment fails, it could potentially cause a catastrophe.
What if it's too hard to take the equipment offline to test?
In certain instances, we can test while you are still online. If you have redundancy, we can isolate and test as needed.
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How much of a problem are harmonics, and how do you isolate them?
In numerous cases, a small part of the system can wreak havoc with the whole. These things can, and should be, dealt with at the time they are installed. However, in most cases they are not. Unfortunately there are no fast and easy cures. Each case is different. We perform a PQ study to determine the issue. Know that this is a long-term project (weeks, not days), but relatively inexpensive. Equipment can be placed and monitored, usually on a weekly basis.
Why does it matter what ratio the multi-ratio CT is tapped at?
Per industry manufacturing standards of CTs, if the available fault current is high enough to produce secondary (of the CT) current levels greater than 20X the CT nominal rating, the CT core can become saturated. For Example: 25,000A available fault current, CT tapped at 600:5 will yield a potential for up to 208.33A on the secondary of the CT (25000/(600/5)). This is well above the 100A (5A X 20) for that particular CT. Most likely the CT will saturate, providing a misrepresentation of the actual current to the protective devices, in most cases the device will see significantly less current than is really there, preventing or delaying tripping of the interrupting device. If the CT was tapped at 2000:5, the secondary current under maximum fault loading would be lowered to 62.5A, well within the accuracy limits of the CT core.
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What advantages are there to upgrading protective relays to newer, microprocessor based units?
This is a very loaded question that can be highly dependent on the intended application, but here are several general reasons to upgrade: Modern relays can perform many functions, replacing several or even dozens of electromechanical an solid state relays. The accuracy, reliability (no solid state electronics to fail), computation power and customization of modern relays completely trumps prior technologies. This provides more intelligent fault detections (and locations), clearing only the faulted section of the system and not interrupting adjacent circuits. The higher level intelligence and accuracy of these relays greatly decreases the potential for nuisance tripping and inadvertent outages. Many microprocessor relays allow communications to provide operations such as control, metering, alarms, indications, fault/event records and protection changes to all be performed and compiled remotely and in-service. Finally, modern relaying has the potential to save money by decreasing preventable and non-preventable outage times and in some instances the up-front costs are even less than replacing the older (rarer) systems as they fail.
What are DGA monitoring systems?
DGA (Dissolved Gas Analysis) monitoring systems are typically implemented on large, critical power transformers. They continuously sample the oil in the transformer's main tank and alarm when gas and moisture levels (generally in ppm) exceed specified levels. Since high levels of certain gases are indicative of equipment and insulation failure, they can provide alarming and real-time measurements to SCADA systems for trending and maintenance scheduling. This has potential to allow for planned outages that maintain loads, instead of catastrophic failures resulting in equipment damage and incidental load losses.
How long will it take for testing to be completed?
It depends on if the work that needs to be done before we can start testing the equipment is complete, and if we have all the correct information of the equipment.
That shouldn't be a problem, just coordinate a time with us and your crew.
Have you ran into this issue on this type of equipment before?
The answer that is given depends. We will try there best to get the issue resolved in timely manner. If we have seen the problem before we have a better idea before we even start the project on what to look for. If it's something we have never seen, then we take all the corrective actions to get it taken care of.
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How long does a typical balance and alignment job take?
The typical balance and alignment jobs takes two to four hours for each. However, there are many factors that contribute to jobs taking longer.
What do I need to be concerned with regarding my DC motor?
DC Motor brushes need to be analyzed for each specific application: key factors are motor loading and atmospheric contaminants. We change brush quantities and grades to maximize commutation, decreasing commutator and brush wear. The commutator should look like an old penny, not a new shinny one. Don't use silicone sealants in the cooling air system, covers, or terminal boxes of any motors with brushes. Polyurethane based sealants are the recommended type. Using dry compressed air, blow out your DC motors at regular scheduled intervals to remove carbon dust and dirt.
Should I go in-house with our Vibration Analysis Program?
You can, but it's only practical if your plant has 2,000 or more bearings that you want to analyze each and every month. The cost of the manpower, training, and equipment cannot be justified without this many bearings being analyzed at a minimum.
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How often should I have vibration readings taken on our equipment?
This depends on how critical the equipment is to production and how quick you can get a replacement unit installed and up and running. We feel paper machine bearings should be done at least monthly. Other support equipment should be done on average quarterly. Widening the interval too much sets the program up for failure.
How can I assess the health of bearings out of physical reach?
We offer two solutions: First, we have a non-contacting laser vibrometer which can take a velocity reading on a bearing housing from as far away as 660 feet, if we have line of sight. The other option is to install permanently mounted vibration/ temperature transducers to this equipment that is tied back to a junction box. Data can either be tied in to your data control system for alarming, or it can be manually gathered during our vibration route visits at the junction box.
Do you provide any permanently mounted vibration analysis hardware that provides alarms?
Yes we do. We work closely with CTC in providing these solutions. CTC offers lifetime warranties on their hardware. L&S can assist you in determining the best hardware for an application and even assist in the installation.
How often should I perform VAP service?
The more times on-site taking data the more effective VAP is. We usually set up a quarterly program. Performing a VAP on a less frequent schedule isn't nearly as effective.
Comparable to most service centers.
What is your lead time for repair jobs?
Standard lead time is five to ten days without rush requests
If I have a "hot" job, what would you do to limit my down time?
We have a 2 shift operation to get your motor back to you faster.
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Local shops are good, but what happens when your guy is on vacation? When it's a one or two person shop, you need a second source for emergencies. We offer 24/7 service. Also, when your guy is out, who knows what color of paint that you need, or what kind of grease that you use? We use a customer checklist so that whoever works on your equipment will have all the information required to properly repair your equipment, what the proper purchase order procedures are, any special repair requirements are, etc. Are they capable of handling the larger HP motors, or are they limited in their lifting capacity. We have cranes that can lift up to 40 tons in our shop. We are diverse enough to handle everything from 10,000 HP motors / generators to small servomotors.
Yes. We have a fleet of trucks waiting for your call.
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How often should I grease my motors?
Each application is different and therefore there is no simple answer. There are many factors involved that determines the frequency of lubrication: 1. Ambient temperature: If the motor is located in a location that has a high ambient temperature, it needs more frequent lubrication. 2. Environmental conditions: Motors located where they are subjected to airborne contaminates need to be lubricated more frequently than those in clean environments. 3. Duty Cycle: A motor that runs 24/7 needs to be lubricated more frequently than one that only runs eight hours a day, five days per week. 4. Motor Speed: A motor running at 3,600 RPM needs to be lubricated much more frequently than a motor running at 1,200 RPM.
How much grease do I use to grease my motor?
The amount of grease used is dependent on the bearing size.
Should I be concerned with greasing my motors too much?
Over-greasing motor bearings is worse then not greasing them at all. Use only long-term grease in grid or gear type couplings. Use only the recommended amount of grease in couplings. Overfilling them causes axial loading on both the drive and driven machines
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At what horsepower range do I repair my motor instead of replacing it?
The standard answer is about 50 HP for a motor that is burned out. However, several other factors may help determine the best course of action. If there is a lead-time issue with the new motor or the existing motor is special in some way, conditions may warrant repairing the motor rather than replacing it.
Can I still purchase the old Reliance motor
that I have used for many years?
Probably not. When Baldor purchased Reliance motors, they eliminated many redundant models. As a result, the Baldor motor may not be the exact same shape or replacement for an old Reliance motor. The best course of action is to review the application and work with a quality motor distributor to find the motor that will most closely meet your requirements.
Are medium voltage motors covered by Energy Independence and Security Act (EISA)?
No. EISA only covers motors that are operational at 60 Hz with voltages through 600 V.
Will a repaired or rebuilt high-efficiency motor retain
their original efficiency?
This idea or misconceptions sometimes leads certain users or customers to purchase new motors rather than repairing the old one. The long and short answer is, we follow all proper procedures to prevent any damage to the core and use the proper calculations for coil design, as specified by the original manufacturer.
What horsepower does it pay to start rewinding a motor?
Usually 25 HP and above unless it is a special motor.
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Does your repair shop have a schedule for calibrating their testing equipment & measuring tools?
We are an ISO certified shop, and we keep records as to when everything was last calibrated.
The model number of my motor ends with a letter. What does that represent? (Wxample 284tcz)
"T" frame motor, "C'" face mounting, "Z' designates special mounting, special shaft, or both.
How does my high-efficiency motor being affect belt drive applications?
High-efficiency motors run closer to synchronous speed than old ones. Therefore, you must change one of the pulleys (usually the motor pulley since it's the least expensive) and change belts to slow the unit down to the speed it was originally running. Not doing this causes more greasing of bearings, motor running hotter.
Why, when looking at purchasing a spare
4 Kv fan motor is the Wk2 so important?
Besides having an existing drawing of original motor, fan curves, and size requirements, no motor manufacturer is able to quote without Wk2. The manufacturer won't guess what the Wk2 should be. If however, unit books don't provide Wk2 information, most often you can go to the fan manufacturer and they can supply you with the fan inertia.
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Can we send in a electronic purchase order?
Your purchase order can be sent to our inside sales department by using the following email address: orders@lselectric.com.
What are your specific location addresses for mailing orders, requests, and shipping repairs?
All of the L&S Electric mailing and shipping addresses, phone and fax numbers, and other important information is found at our website: www.lselectric.com.
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Where can I find motor and drive
data for equipment I have bought from L&S?
Manufacturer information on products we sell and support is found on our website, www.lselectric.com. We provide links to each manufacturer's website. You can lookup any data, such as drawings and performance data, for your specific product in question.
Some companies receive kickbacks at the end of the year based on how much they buy from them. The problem is, they typically don't have the products on the shelf locally. They have to bring it in from their regional warehouse. When you are in a breakdown situation, you need the product immediately. Management typically understands that they lose more money by not producing their product for a few days, than they gain by using a source that doesn't have the product on hand. These chain parts houses are responsible for handling everything from drives, electrical products, to chain, sprockets, bearings, and conveyor widgits. While they are very capable people, they can't be an expert on all their products. We focus on our core business, that is, everything from the incoming power to the reducer. We don't try to be experts on everything. We do have a level of expertise for everything we sell. Furthermore, we have the capability of repairing everything we sell. You wouldn't want to buy a car from someone who can't repair it if it fails under warranty, would you? We stand behind everything we sell, and we won't say, "...we don't handle the warranty on this. Take it to someone else."
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- home
- contact us
Logo
About Us
- About L&S Electric
- Frequently Asked Questions
- Glossary of Terms
- AC Motor Theory (pdf)
- DC Motor Theory (pdf)
- Basic Electricity
- Electric motors explained using animations and schematics
- Case Studies
- EASA AC Motor Guide (pdf)
- Understanding Energy
Efficient Motors (pdf) - Fraction & Temperature Conversion
- Key Frame Dimensions
- Technical Motor Specification
- Frame Dimensions for
Foot Mounted AC Motors - IEC Frame Dimensions (pdf)
- Do's & Don'ts for Ball Bearing Assembly
- Lubrication Information
- Relubrication Intervals
