Uninterruptible Power Supplies installed in harsh environments

Uninterruptible Power Supplies installed in harsh environments

Harsh Environments

When a UPS is installed outside of a perfect environment, how can the effects be mitigated?

Uninterruptible Power Supplies installed in harsh environments

The ideal environment for an Uninterruptible Power Supply (UPS) and it associated battery set, would be in an area that is secure, dust free, dry with an ambient temperature maintained between 20-25C and adequate airflow to meet the manufacturer requirements.

When installing a UPS as part of a new build project or renovation works, the environmental requirements are usually carefully considered and the UPS will be ideally located in order to increase reliability and maximise the operating life.

Sometimes, if the UPS is retrofitted to an existing electrical infrastructure, the ideal environment often isn’t physically available. With poor planning, designers locate the UPS alongside other electrical equipment, such as switchgear located in plant rooms, basements or even outdoor containers. The UPS then may have to contend with the elements of a harsh environment. If this is the case, how can the effects of a poor environment be mitigated?

Separate Battery Location

The operational ambient temperature of the majority of UPS models is specified as 0C to 40C (assuming no condensation), in this window the UPS will perform without a serious effect on its overall life, as long as consumable components such as capacitors are preventatively checked and replaced when required. The batteries however are a completely different story. Although the specification sheets will state a similar operational window, the service life and performance, drastically alter depending on temperature.

Most battery manufacturer specification sheets state the performance characteristics and service life at 20C. If the temperature is higher, the performance will increase but the lifetime will decrease. If the temperature is lower, the lifetime will increase but performance will decrease. Its a very substantial drop off, the specification of a Yuasa five year design life shows that with an ambient temperature of 30C, the battery would only be useable for 33% of its design life. That’s just over 1.5 years!

One method to remedy this would be to construct a dedicated area just for the battery installation, which is temperature controlled. This also helps with power savings, as batteries give off minimal heat (unlike a UPS). If the temperature cannot be maintained then select longer design life batteries such as ten or twelve year blocks and check their performance regularly. Although initially more costly, it avoids annual battery replacements and a ten year design life battery is not twice the cost of a five year block.

Dust Filters

In normal operation, the UPS is always running and so a constant flow of air enters and exits the system. If the environment is prone to dust or other airborne particles, the inside of the UPS can become clogged, not only causing cooling problems but coating the internal components with debris and potentially causing failures. Selecting a UPS which features dust filters as standard or which have the option for retrofitting and regular replacement will prevent harmful internal build up of dust compromising the reliability of the system. In extremely poor environments “Conformal Coating” may also be recommended, see below.

 

Conformal Coating

As already mentioned, the ambient air (and associated airborne particles) are blown through a UPS constantly throughout its service life. Where the air may have moisture present, a chemical contaminant or high humidity content, some manufacturers offer the option to apply a “conformal coating” (sometimes called tropicalisation) to the internal circuit boards. The Conformal Coating is a protective chemical coating applied by the manufacturer before shipping. By being electrically insulating, it maintains long-term surface insulation resistance, thus protecting the electronic assemblies from air-borne contaminants such as salt spray, which will assist in preventing corrosion. This procedure was historically used for “industrial” UPS, but now manufacturers such as Huawei and AEC use this technology as standard on their three phase UPS range.

Summary

Cooling fans degrade over time and have a service life of around five to seven years under good environmental conditions, it is rare a single fan may fail before this time, but if so it should be replaced as soon as possible.

Arranging for a preventative replacement of all the cooling fans at a fixed interval is the most cost effective method by saving on labour expenses and arranging maintenance windows. It is also the best way to increase the reliability of performance of the UPS, reducing the chances of losing the connected load and costly downtime.

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Component Failure

Component Failure

Component Failure

A blog about UPS capacitor and fan replacement and how to prevent UPS failure through preventative maintenance.

Component Failure

With the exception of the battery system, there are two other critical functioning components which have a finite life and are integral to UPS performance, they are the Capacitors and Cooling Fans. Failure of either could cause the loss of connected load, the premature ageing or destruction of other components and result in costly downtime. Here we discuss the reasons why, some frequently asked questions and how to best to avoid this drastic outcome.

Cooling Fans

Why do UPS cooling fans fail and need replacement?
Cooling fans are one of the few UPS components that are mechanical in nature, they run continuously while the UPS is online and therefore are subject to mechanical wear.

The electronic components inside a UPS switch at a very high frequency and so create a tremendous amount of heat. For instance a 200kW UPS system running at nominal load and operating at 95% overall efficiency will generate around 10kW of heat, this heat needs is expelled by means of the cooling fans moving a tremendous amount of air through the UPS.

Sealed bearings inside fans contain grease, which dissipates over time due to increased temperature. This results in the fan speed slowing which in turn creates more heat and noise. The build up of dust on the air intakes also increases the temperature and forces the fan to work harder to keep the air moving.

Single Fan Failure

Most UPS manufacturers design their UPS to operate in ambient temperatures up to 40°C at nominal load and sometimes contain redundant fans. As ambient temperatures around the UPS are typically lower and not run at full load, if a single fan fails, the UPS may continue to operate online for a short period of time until the fan is replaced. It is not recommended to continue running for long periods with a defective fan as internal component temperature will rise and subsequent premature ageing will occur.

Multiple Failure

If multiple fans fail and the internal UPS temperatures rise above an operating threshold the UPS will normally transfer to static bypass, although the connected load will continue to be powered by raw mains, it will be susceptible to input power variations and remain unprotected from outages. The fans should be replaced immediately and the UPS restored to an online condition.

Do I know when my fans will fail?

It is possible that before a total failure the fan will start to make audible noise as the grease dissipates and fan bearings start to run dry. Some manufacturers also have tachometers, which will sound an alarm when the fan speed decreases below an acceptable level.

The cooling fans’ service life is affected by the ambient temperature around the UPS, the environment and the load level applied to the output of the UPS.

Preventative Replacement

Most manufacturers recommend a preventative replacement at between five and seven years. Although replacing fans that have not yet failed may seem wasteful, the cost of an individual fan is normally significantly less than the associated labour expense of a UPS engineer along with the time scheduled to take the system offline to complete the replacement. Not only will the preventative replacement of fans be more cost effective than replacing them individually as they fail, it will also minimise the period of time the connected load is at risk while running on mains power while the UPS is in bypass mode. As capacitors typically have the same service lifetime, it can make sense to replace both sets of components together. See capacitors below.

Summary

Cooling fans degrade over time and have a service life of around five to seven years under good environmental conditions, it is rare a single fan may fail before this time, but if so it should be replaced as soon as possible.

Arranging for a preventative replacement of all the cooling fans at a fixed interval is the most cost effective method by saving on labour expenses and arranging maintenance windows. It is also the best way to increase the reliability of performance of the UPS, reducing the chances of losing the connected load and costly downtime.

Capacitors

Capacitors are components inside the UPS that smooth out fluctuations in electrical voltage. A three phase UPS may contain hundreds of capacitors, connected in banks for specific roles. They dampen out any changes filling in the troughs and eliminating the peaks to maintain a constant level. They are used for both DC (Direct Current) and AC (Alternating Current) power circuits within the UPS.

How long will my capacitors last?

Capacitors have an operational lifetime calculated by the manufacturer according to the rated voltage, current and ambient temperature. The lifetime can be optimised by avoiding running the UPS at full load or with a high ambient temperature, but the capacitors are consumable and will fail during the service life of the UPS. Depending on the manufacturer, this is usually between five to seven years. Capacitors should be visually inspected and checked during each service visit.

When should I replace my capacitors?

Waiting for ultimate failure of the capacitors will usually cause damage to surrounding components and possibly cause an interruption to the UPS output, especially if the AC output capacitors fail. Replacing the capacitors as a preventative measure when checks show signs of distress or when recommended by the manufacturer will avoid a UPS failure and potentially costly downtime.

Should I only use OEM components?

The capacitors installed by the original equipment manufacturer (OEM) should be of a premium tested brand and will have a specific voltage rating (Voltage), a storage potential (Farad) and physical dimensions. Where OEMs have experienced premature or unexplained failure of capacitors, they normally would switch to another premium brand during manufacturing lifecycles. The replacement components, should as a minimum meet the original specifications. Requesting the specifications of the components will allow a user to find a comparative quotation, but this will need to be requested or recorded during the service visit as normally a manufacture specific part code will usually be quoted.

Summary

Prevention is better than the cure. The AC and DC capacitors are of a limited service life which is normally shorter than the service life of the UPS. Regular checks of the capacitors during servicing and replacement when issue arise or when the service life has been reached avoids larger issues caused by capacitor failure. Capacitor failure has been the cause of fire suppression being triggered, damage to other internal components, loss of load and even fire. The preventative replacement of all the capacitors once signs of raging are apparent helps avoid these major issues. As capacitors work together in banks, if one fails it is often more cost effective in site labour and downtime to complete a full replacement.

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Battery Failure

Battery Failure

Battery Failure

A blog about UPS batteries and battery failure explaining the different types of failure you may experience and why this may occur.

Battery Failure

The quality of a UPS battery can vary depending on the manufacturer, however even the highest standard of battery have a finite life.

The lead acid battery is essentially a “living” product and will slowly discharge during storage, this can be minimised by lowering the storage temperature and regularly recharging the battery. The charging method is important to be completed correctly as attempts to use a rapid charge will cause damage to the active material within the block and reduce the battery life. The manufacturer recommendations should be consulted for best practice in storing and charging batteries in excess of three months.

Battery faults can occur either because of manufacturing defects or issues caused by incorrect installation and usage. Here we discuss the different problems that can arise from either.

Non Manufacturing Defects

Physical Damage

This occurs when a battery is stored, transported or installed without due care. Damage can occur internally when the outer casing of the battery is dropped or banged. The manufacturers packaging should be used for transportation and care should be taken during the installation. Batteries should never be stood on or even stacked during install without protective packaging. If the connectors to the batteries are bolted too tight then structural damage between the terminals and plates can occur. If the connectors are too loose then a higher electrical resistance will cause a build up of heat. During installation or replacement the connections should be fastened inline with the recommended torque values available from the manufacturer.

Sulphation

When a battery is left in a discharged state for a period of time, a chemicial reaction occurs. This reaction is called “sulphation” and will permanently cause damage to the battery performance. The typical visible signs of sulphation are a white coating on the positive terminal and an unoxidised metal glaze on the negative terminal.

The damage can occur if batteries are fully discharged when connected to a UPS during a mains failure and then isolated, or when not immediately recharged when mains power returns. Another common issue is where the UPS is powered down, but the batteries are not isolated. This will cause the batteries to constantly and very slowly discharge through the UPS DC capacitors until they are at their lowest point. The longer the batteries are left connected, the greater the sulphation reaction. Batteries are not normally recoverable once this has occurred.

Over Cycling

UPS batteries are designed for standby use for a high power discharge over a short period of time, typically five to fifteen minutes. The batteries can only withstand a limited number of cycles (discharge and recharge) as opposed to “cyclic” batteries, which are used in motorised vehicles and are designed to cycle daily. When a battery is cycled, a small amount of active material is permanently lost from the plates and battery performance reduces. It is typical for a new battery to perform up to seven percent above the designed specification, which allows for initial autonomy testing during installation and commissioning. However, regularly discharging the battery in excess of 35% of its capacity for testing purposes will severely shorten the service life. If the UPS has a five minute autonomy when new, then a two minute battery test once a month is a sure way to damage the batteries within the first year of operation. If the batteries are connected to a long autonomy system, for example three hours or more, the cut off voltage of the UPS inverter should be adjusted to a higher value in order to prevent a deeper discharge of the battery at regular intervals.

Overcharging

The charging characteristics of the batteries should be set as per manufacturers recommendations during installation or replacement. If the charging voltage or current applied from the UPS is too high, the batteries overheat and electrolyte will start to evaporate. The overcharging will accelerate the breakup of active material, the batteries could even swell or burst and excess hydrogen will vent. This is a serious condition and emergency measures should be taken immediately. It is common for overcharging to occur where original batteries have been replaced with a smaller capacity or few number of blocks and the UPS charging characteristics have not been adjusted to compensate.

Undercharging

Undercharging occurs, where the UPS is not capable of applying an acceptable charge voltage or current to restore the batteries to a full state of charge. This will slowly cause sulphation and the battery performance will degrade. This typically happens where the battery set requires more charge current than the UPS can physically deliver or when it has been configured incorrectly.

Manufacturing Faults

The manufacturing standards of leading OEM providers such as Yuasa, mean the manufacturing defects can occur but are rare. Obviously manufacturing faults are more common in cheaper brands where lower quality manufacturing techniques and materials are utilised.

Short Circuit / Dead Cell

This is typically seen in batteries designed with a shorter service life. One cell within a battery will show a dramatically lower acid specific gravity than the others. During a high discharge the problem cell will boil and the battery will not recover correctly during a recharge resulting in sulphation.

Internal Break

There will be no voltage reading at the battery terminals as there is a structural internal break within the battery. Each individual cell will have a good specific gravity reading.

Summary

Providing a high quality battery, which is stored, installed and configured correctly with a UPS will ensure the amount of battery faults will be minimal. All batteries have a finite life, but the service life can be extended by using a battery system in the correct environment, regularly checking and recording the charging and discharging characteristics, along with setting the UPS charging parameters to match the battery set.

If you would like to have a battery set checked to ensure it is operating to reach its design life, require a replacement proposal or have a new battery set installation contact UPS Power Services for advice.

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Why consider UPS maintenance?

Why consider UPS maintenance?

Why do I Need UPS Maintenance?

A blog about UPS Maintenance and what a UPS System is used for.

Why UPS Maintenance?

Uninterruptible Power Supply (UPS) units are often the first line of defence to protect your critical load equipment. They constantly take the incoming mains power complete with spikes and surges and perfectly regulate a clean stable power output.

Careful planning and significant investment goes into UPS as part of a power protection strategy and even business continuity planning. When your UPS is working correctly, you will forget it is there. But should you?

Once a UPS is installed and commissioned it can sometimes be left until it next alarms before giving it a second thought. With UPS becoming a commodity item and initial product price decreasing some manufacturers now start to charge a premium for ongoing service and “maintenance”. But what exactly is entailed in that “maintenance”? That’s why some of the most prevalent questions I have had from users over the years is, what should I include in my UPS service and maintenance agreement? Do I even need one?

What is a UPS?

A UPS is an electrical device designed around sophisticated electronics enclosed in a metal or plastic box. With exception of the cooling fan it has no mechanical moving parts like a standby diesel generator, so what could possibly require maintenance? In actual fact very little and the term “maintenance” for works performed during a visit to a UPS is probably now used incorrectly. There is very little if any “maintenance” that can even be performed on a visit from an engineer to a UPS unless he is specifically replacing aged parts. So, why do I need an agreement or contract?

Although the cooling fans are probably the only mechanical moving parts on a UPS (They can be cleaned or in some case greased). The remainder of the unit is designed around electronic devices that switch fantastic amounts of electrical power tens of thousands of times a second. This is all driven by algorithms written in firmware controlled by Digital Signal Proccesors (DSP). These complicated electronic switches have a design life and will eventually wear out and fail when used for long enough in the wrong conditions or environment. When they do fail, they will most likely go short circuit, which will result in one of the most loudest bangs you will ever hear accompanied by some smoke which may set off any fire suppression present. What follows (after the fire brigade) is a long investigation into what happened from various specialists, consultants, engineers and worried managers.

UPS operating conditions

These devices (which are basically complicated switches) are designed to run for up to tweny years, but only under the environmental conditions and loading limits they were designed and manufactured for.

Therefore a vast majority of the time utilised on a UPS engineers “service” visit as part of a service agreement or contract involves checks. Basically checks that the UPS is operating in the correct environment under the correct load and isn’t being damaged by any external factors. Some of these “checks” can and are completed daily by the user. The temperature of the UPS room, safe output loading of the UPS, even for the adventurous the use of the inbuilt battery testing function while following the basics of keeping the UPS area free from excessive dust, moisture, clutter or cups of tea (Yes all too often UPS units can make handy shelves)!

However, just as important as these basic routine checks are the ones that must be completed by an experienced UPS engineer.

The technical stuff

Upon learning the correct switching procedure and safely shutting down the UPS, whilst maintaining critical load through the bypass line, the UPS can then undergo a detailed visual check of all components, connections can be checked and tightened if necessary, signs of corrosion can be noted and excess dust deposits can be removed should the environment be harsh. The DC & AC capacitors, IGBT devices and batteries should be visually inspected for signs of budging, leakage or overheating – all are signs that the components may be failing (or approaching that Bang scenario).

If the visuals check out, the UPS engineer can then restart the UPS and take on-load readings. The DC side of the UPS can be measured for AC ripple of both voltage and current (High ripple on the DC could indicate worn capacitors or aged batteries). The measurement of the output AC waveform can highlight aged AC filter capacitors. Analysing the input power to the UPS can also highlight mains issues such as high harmonics, poor power factor or even just high voltage – for short periods of time the UPS is designed to filter these mains issues from the critical load, but permanent running with higher than nominal input voltage or high harmonic content will cause the premature aging of components within the UPS. If the external factors cannot be rectified, this should be noted and recommended action be taken in due course.

Whilst a user will be able to clearly see any current alarms on the UPS, usually it is only the UPS engineer that is able to download and analyse detailed history logs of conditions the UPS has been subjected to and how it has behaved since installation (or the last service visit). This is all vital information for predicting how long components such as capacitors and batteries will have a useful life for.

Finally, firmware, depending on the age cycle of your UPS it may have a newly updated version of firmware for control of the sophisticated electronics. Only an experienced and trained UPS engineer should attempt this (and if anything doesn’t go to plan, you want him there anyway!). New firmware is vital to prevent you experiencing unexpected events, which unfortunately other users of the same product may have already reported. An upgrade protects you so well worth insisting upon, especially if the manufacturer recommends it.

Sophisticated job tracking

With our sophisticated job management software, we are able to ensure you, the customer gets a timely report as soon as the service has been undertaken. Our engineers have access to your system information, parts schedule and potential likely issues based upon the history of the UPS. This means we are always prepared before we arrive on site and are able to ensure your system is carefully looked after for the duration of it’s life span.

Our findings

Finally, all of the findings during a service visit should be communicated to you in a swift, clear and transparent method. You can then make decisions or ask for assistance or recommendations in actioning.

So, after reading my thoughts on the above, in answer to our questions, what should I include in my UPS service and maintenance agreement? You should ensure that as a minimum all elements discussed above are completed during the visit, then communicated clearly to you along with any potential risks and recommended actions are followed up. Do I even need one? If the UPS engineer is just going to turn up check for green lights then ask you to sign a piece of paper, Id probably just save your money and wait for the Bang.

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Modular UPS systems versus standalone

Modular UPS systems versus standalone

Modular versus standalone UPS

A blog about the benefits and pitfalls of modular ups systems against standalone ups systems.

Modular UPS Systems Versus Standalone UPS Systems

Snowballing power requirements, improved component technology along with increasing user demand over the past five years have now driven modular UPS systems to be designed, specified, and supplied by all the leading UPS manufacturers.

Mark Trolley, Commercial Director of UPS Power Services Ltd talks about the reasons for the move away from traditional UPS technologies and highlights some points of interest when comparing modular and standalone UPS technologies.

“Anti” modular UPS arguments no longer make sense…

Where once modular UPS was frowned upon for being “unreliable” either because of an increased component count over standalone units, a single point of failure on the output static switch or redundant power modules only having a single controller, modular UPS are now a seen as the elite of UPS technology and the future of the industry.

Complex switching algorithms controlling the accuracy of load sharing between tens of power modules all connected together, show efficiency increases and also prevent circulating electrical current prematurely ageing components. Centralised or decentralised static switch technology now overrides the single point of failure argument. Static switch modules can now be removed and replaced “live” while load continues to be powered by the UPS inverter and the DSP controllers located on each module with redundant frame controllers allow power modules to be hot swapped or even removed without interruption to the load.

Maintenance and service

During the service and maintenance period of a UPS, the connected loads are normally transferred to bypass (raw mains power) for safe working requirements. During this time the connected equipment is without any power protection and vulnerable to any mains electricity variations.

 

Is my UPS really standalone?

Many “standalone” UPS systems, also referred to as “monolithic” or “solid state” by vendors are actually made up of internal components set out in a modular layout. Some manufacturers contain a number of physical modules with a single display and control screen with one covering front door, others have the internal components set out in a number of smaller power ratings which are then connected in parallel. One of the reasons for this is now the sheer scale volume in production of smaller switching semiconductor components compared to the lower number of larger semiconductor components. The vast scale of production means using three or four times the number of components is still more cost effective than using larger semiconductor devices. The components can also be set out more efficiently for heat dissipation saving physical space and increasing power density of the unit. It also reduces production time for the UPS manufacturer as only a limited number of power ratings need to be sourced and stocked. Therefore, You may find that your standalone UPS is actually of internal modular design and construction anyway.

Low Loading Efficiency

When a UPS is first specified, it is nigh on impossible for a user to know the total loading throughout the UPS service life, especially where the UPS supports a growing infrastructure company such as a colocation datacentre. Even when the load is accurately calculated and achieved, a “safety” factor is added to the load in order to to size the UPS in event of of any overload conditions, future server upgrades or unbalanced deployment of load across the output phases.

Like any electrical device a UPS would usually be most efficient operating at 100%, but this is neither practical nor possible in reality. While standalone UPS have been optimised to provide high efficiencies at mid loadings, the user will have to choose between future power availability or maximum efficiency, based on the capacity installed on day one.

Advanced modular UPS allow a certain number of modules to be hibernated or switched off if the load decreases or is initially lower than expected, not only does this add extra redundancy but it also allows the other power modules to run at a more efficient loading. To ensure all modules “age” at the same rate, modules can even be cycled to utilise all components for the same period of time. If the loading is not as expected or decreases, the user can physically remove modules as required.

Growth

Power modules are usually mounted into a UPS frame, which may contain a manual bypass switch, main controllers and static switch depending on the manufacturer. While the frame size along with the supply switchgear and cabling determines the total growth in power, a user can start with a lower number of power modules and add further modules, as and when load requirements increase. Thought should be given to the correct mains supply protection for day one capacity and future additional battery requirements, but if these are considered, modular UPS can be deployed as they are marketed on a “pay as you grow” or “scale up as required” basis. Users should ensure that the same modules will still be available from the manufacturer when required.

Cost

The cost effectiveness of modular UPS against standalone units completely depends on the power infrastructure requirements. For example if a user simply requires a 200kVA UPS, then a standalone unit will be more cost effective than a modular UPS frame with four x 50kVA power modules. If however the user requires an element of redundancy, then five x 50kVA power modules in one frame will usually be more cost effective than two x 200kVA standalone UPS. The physical space requirement, electrical supply and battery configuration will also be massively reduced.

Conclusion

Modular UPS systems are now dominating the mainstream marketing of the large UPS manufacturers and analysts predict the future market growth rate of modular UPS to overtake traditional standalone systems. To determine which technology will be the most resilient, efficient and cost effective for use, the user and sites requirements should be carefully considered. If the resilience and efficiency required are within acceptable limits from both technologies, it may be a choice of upfront purchasing costs (CAPEX) where standalone may be better vs the operating costs (OPEX) over the lifetime of the UPS. The future servicing and electricity costs along with manufacturer support and availability should also be considered.

There are advantages and drawbacks for both technologies and each site requirement will differ, so discussing your particular power protection requirements with an experienced, helpful and honest UPS specialist such as UPS Power Services will assist in determining which is the correct choice for you.

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