Nov
18

The Unknown Danger of UPS Batteries

How removing the input transformer has affected the servicing of UPS batteries


Uninterruptible power supply (UPS) systems have come a long way since the original designs of the 20th century. Many of these improvements make systems more reliable, faster to repair, and safer for service personnel. Manufacturers have worked hard to reduce the weight, size, and cost of the systems, giving end-users additional space for IT equipment. One way they have accomplished this is by removing the input and output isolation transformers. The advantages and disadvantages have been discussed in numerous articles and whitepapers. This article specifically examines how removing the input transformer has affected the battery plants and the ability to safely service them.

The ABCs of a UPS
Reviewing the basic building blocks of a UPS system can help us understand how removing the input transformer would affect the operation of UPS system and the battery system.

The original double-conversion type UPS system (Fig. 1) was made up of the following:
• Input transformer
• Rectifier
• Inverter
• Output transformer
• Static switch
• Batteries

 Fig. 1. This diagram shows the basic building blocks of an original double-conversion type UPS.

The first component is the input transformer, which performs several functions, including: isolating the UPS system from the electric utility system, allowing for a 12-pulse rectifier, and reducing input current distortion. Of course, it can also be used to change the input voltage from one level to another. For example, a 480V source could be stepped down to 208V.
The next major component in this type of system is the rectifier. The primary function of the rectifier is to convert incoming AC power to DC power, which can then be used to support the input to the inverter and charge the batteries.
Continuing across Fig. 1 is the inverter, which converts DC voltage to AC voltage and supplies power to the output isolated transformer. The output transformer supplies conditioned power to the critical load.
A static switch, shown above the rectifier and inverter, is used to transfer the critical load from the inverter to the bypass line if there is a failure of the UPS system or if maintenance is required.
The last component in this type of system is the batteries. If input power is lost — typically because of an electric utility outage — then the batteries provide power to the inverter.

Risky removal
One advantage of the input transformer is that it isolates the batteries from the ground reference. The input transformer on these systems prevents a voltage potential between the DC bus, including the batteries and ground. If a short were to occur between the two, there would be no return path for current, and it could not flow (Fig. 2). If a battery did short to ground, then most systems have a circuit that would alarm. The system would often continue to operate until it could be shut down and the danger eliminated.

Fig. 2. The input transformer on a double-conversion type UPS system prevents a voltage potential between the DC bus, including the batteries and ground. If a short were to occur between the two, there would be no return path for current, and it could not flow.

With removal of the input transformer, the DC bus is no longer isolated from ground. There is both AC and DC potential between the batteries and ground, which includes the racks and cabinets. Because of this potential, if any conductive material (including humans) is connected, then current could flow through the item. This could lead to damaged tools, batteries, and racks or worse — injury or death of personnel (Fig. 3).

Fig. 3. With removal of the input transformer, the DC bus is no longer isolated from ground, which ultimately could lead to damaged tools, batteries, and racks or worse — injury or death of personnel.

Maintenance considerations
It's common practice on the original double-conversion type UPS systems to perform as much battery maintenance as possible while the UPS system is online supporting load. This allows for the critical load to stay protected during battery maintenance.
Vented batteries often have four preventive maintenances (PM) visits completed per year, while the UPS system has two. The two additional battery maintenance visits can be completed with very little risk to the critical load, allowing for the work to be completed during normal working hours.
Valve regulated lead acid (VRLA) batteries typically have two PM visits per year in conjunction with the UPS system. The battery maintenance is completed while the UPS system is online. Or, if it isn't a major UPS system inspection requiring a transfer to bypass, the batteries do not have to be taken offline at all.
Over the last 10 years, a few manufacturers have started supplying VRLA batteries inside a container often referred to as a "battery can" or "battery module" (Fig. 4).

Fig. 4. Some manufacturers have started supplying VRLA batteries inside a container often called a "battery can" or "battery module."

Modular battery systems have the same electrical dangers as open racks or battery cabinets. However, because the batteries are enclosed in a sealed box, there is no chance they can come into contact with personnel or ground. This gives a built-in safety feature during maintenance, because all the battery connections are enclosed and can't come into contact with tools or personnel.
Although modular batteries require periodic maintenance, it's not as invasive as traditional VRLA or vented batteries. Instead of using specialized test equipment to test each jar's voltage, internal resistance and specific gravity, if applicable, the UPS system runs a battery test at preprogrammed dates. If a problem is found, an alarm is generated, and appropriate personnel notified. This essentially eliminates risk to service personnel because there is no contact with the batteries while the system is online.

Battery most likely to succeed?

Over the last several years and for the foreseeable future, the use of lithium-ion (Li-ion) batteries to support UPS systems continues to increase. Again, the electrical danger of removing the input transformer would be the same as lead-acid batteries. However, much like the modular battery systems, the danger is reduced by the type of installation and the maintenance that is required. Personnel would not be exposed to the DC bus, and this reduces risk.
An example of the dangers involved can be seen in a recent event that occurred when a modern UPS system without an input transformer had an annual PM performed on its batteries. During the PM procedure, bolt re-torque activities were being completed. There was not enough clearance for an insulated torque wrench so the technician used his uninsulated torque wrench. After completing about half the plant, the technician's wrench made contact with a battery-retaining bracket while still in contact with the terminal bolt. This caused a bolted fault between the DC bus and ground, resulting in damage to the battery post, the battery rack, and the torque wrench (Fig. 5). Thankfully, the worker suffered no injuries.

Fig. 5. While performing an annual PM on its batteries, a technician's wrench made contact with a battery-retaining bracket while still in contact with the terminal bolt. This caused a bolted fault between the DC bus and ground.

Risk reduction
Using Li-ion or modular batteries would have prevented this incident from happening. However, not all installations are Li-ion or modular. What can be done to reduce the risk to personnel on these systems?
First and foremost, educate everyone who will be working with or around UPS systems of the dangers involved. In addition, use insulated tools and provide barriers where possible to prevent anyone from coming into contact with uninsulated battery terminals.
Whenever possible, all maintenance should be completed with the batteries disconnected from the UPS charging circuit. This will prevent a return path for current if contact is made between any battery connection and ground.
As with any service work in the electrical field, it's important to understand any and all dangers before working on or near equipment. Wherever possible, reduce or remove the danger before work is started. This not only protects the equipment but, more importantly, it also protects you.

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See the original full article at: https://www.ecmweb.com/maintenance-repair-operations/unknown-danger-ups-batteries?NL=ECM-06&Issue=ECM-06_20191114_ECM-06_444&sfvc4enews=42&cl=article_3_b&utm_rid=CPG04000000918978&utm_campaign=29850&utm_medium=email&elq2=51903991678140c69eea754044caac67&oly_enc_id=6901B0580289B1P

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Nov
07

Modernize or Outsource: Evaluating your Data Center Options

Don't risk availability... Upgrade your infrastructure! 

Do you know you can boost efficiency as much as 67% by upgrading your aging data center? Many improvements to existing performance can be both simple and cost effective. Before making a decision, it's best to look at the facts:

  • Modernization choices
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Explore your options with our free reference guide, "Modernize or Outsource: Evaluating your Data Center Options.

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See the original full article at: https://www.eaton.com/us/en-us/company/news-insights/news-releases/2019/eaton-tvs-boosts-new-2020-ford-mustang-shelby-gt500-supercharger.html

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Nov
04

Eaton TVS supercharger boosts new 2020 Ford Mustang Shelby GT500

Power management company Eaton today announced its TVS R2650 supercharger helps boost the hand-built and Ford Performance-tuned, 5.2-liter V8 engine that powers the all-new 2020 Shelby GT500, the pinnacle of Ford Mustang performance.

The Eaton TVS R2650 supercharger is the evolution of the popular Twin Vortices Series (TVS) platform, which features a patented rotor coating for improved efficiency. The high-twist, four-lobe rotor design is 15 percent larger than the TVS 2300 supercharger found on the previous Shelby GT500 and features several improvements to maximize efficiency and improve performance at higher speeds.

The Eaton TVS R2650 supercharger in the all-new Shelby GT500 provides up to 12 psi of boost, helping to produce 760 horsepower and 625 lb.-ft. of torque, both of which make it the most powerful street-legal Ford ever and the most power- and torque-dense supercharged production V8 engine in the world.

Several technical modifications help this supercharger deliver supercar-level power and torque, including a 170-degree helical twist of its rotors, which is 10 degrees greater than previous TVS rotors. Other upgrades include bearing plate pressure relief points that reduce trapped volume pressure and optimized sealing for better flow efficiency.

Proudly crafted in the United States, the 2020 Mustang Shelby GT500's engine is hand-built at the Ford Motor Company's Romeo Engine Plant in Romeo, Michigan, and its innovative TVS R2650 supercharger is assembled at Eaton's Vehicle facility in Athens, Georgia.

"We are proud to collaborate with Ford Performance to help it produce the most powerful Mustang and street-legal Ford ever," said Karl Sievertsen, chief technology officer, Eaton's Vehicle Group. "As the world leader in supercharger production, we are committed to innovation that helps our valued customers achieve the best possible performance out of their vehicles."

Eaton has produced more than 7.5 million superchargers globally for a variety of applications.

While Eaton's TVS technology has long provided boost to high-performance vehicles, the technology also is used for advanced combustion engines, providing exceptional transient response with precisely metered air flow at any engine operating condition, independent of exhaust gas enthalpy. This is critical for new engine concepts, where high levels of air are often required at operating points at which turbochargers are limited.

As part of Eaton's commitment to the quality of life and the environment, TVS technology continues to evolve to enable cleaner and more efficient engines. The positive-displacement TVS technology provides the required airflow conditions precisely and instantaneously and can also deliver an additional boost in power. TVS technology can be driven mechanically or electrically, providing flexibility for automakers as they look to a more electrified future. TVS technology also is used in hydrogen fuel cell applications, as this technology often requires high levels of pressurized air at certain operating points.

The flexibility of Eaton's TVS technology even goes beyond automotive applications, enhancing performance in the personal watercraft industry and providing accurate airflow in industrial applications.

Eaton is a power management company with 2018 sales of $21.6 billion. We provide energy-efficient solutions that help our customers effectively manage electrical, hydraulic and mechanical power more efficiently, safely and sustainably. Eaton is dedicated to improving the quality of life and the environment through the use of power management technologies and services. Eaton has approximately 100,000 employees and sells products to customers in more than 175 countries. For more information, visit Eaton.com.

GT500 and Shelby are registered trademarks of Carroll Hall Shelby Trust. Horsepower and torque ratings are based on premium fuel per SAE J1349 standard. Your results may vary. 

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See the original full article at: https://www.eaton.com/us/en-us/company/news-insights/news-releases/2019/eaton-tvs-boosts-new-2020-ford-mustang-shelby-gt500-supercharger.html

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Oct
21

Explore Galaxy VS 3-Phase UPS from Schneider Electric | Schneider Electric

 Increased availability. Reduced operating costs. First class power protection for critical infrastructure. 

The Galaxy VS is a highly efficient, modular, easy-to-deploy 10-150 kW three-phase uninterruptible power supply (UPS) that delivers top performance to critical IT, commercial, and industrial facilities. You need best-in-class power protection that is as high-performing and innovative as your business is. Galaxy VS maximizes your availability while minimizing your total cost of ownership, with highly efficient patented technologies and modular architecture.

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09

Schneider Electric Innovation Days: Design Engineer Seminar 2019

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