Kehua Tech, the international branch of Zhanzhou Kehua UPS in Xiamen, China has redesigned it’s range of 3, 5 & 6KVA online double conversion rackmount Uninterruptible Power Supplies (UPS). Gone are the hardwired outputs replaced with 16A and 10A IEC outlets for connection of rack PDU’s and direct connection to equipment. In addition to the RS232 interface a new USB port has been added for ease of connectivity with modern computer systems that may not have DB9 ports.

A new Emergency Power Off (EPO) port has been added to ensure that should an emergency occur the UPS can be made dead in an instant and not continue to provide power to the load in case of emergency.

These systems are designed with runtime in mind and so they require external battery cabinets that provide 38 minutes full load runtime on the 3KVA and 20 minutes on the 6KVA. Additional cabinets can be added as required extending autonomy into the hours should this be necessary. What’s more – unlike similar systems that boast long runtime capability, these systems come with a 4Amp charger as standard (rather than the normal 1A charger in most comparable systems) ensuring that your batteries are charged expediently following an outage.

For integration with standard data centre environments, the cooling fan takes cool air from the front and exhausts this from the rear, ensuring that the UPS will meet with any hot aisle/cold aisle configuration.

The full system is rack mountable, or free standing should you require. Occupying no more than 5U of rack space, the KR-J-F series is the latest on the highly competitive Kehua Tech range of UPS. Available exclusively through Power Inspired Ltd.

KR6000-J-F 6KVA Online Double Conversion UPS

What is a redundant power solution? Well it’s one where you have more UPS than you actually need to power the load. Typically referred to as an ‘n+1′ redundant solution, where ‘n’ is the number of systems you ordinarily require.

It’s achieved in the main with UPS systems that communicate with each other and effectively share the load. Such systems are usually in the high power three phase category. It is unusual to find any systems at low power ratings that can do this. What’s more, you will need a special output distribution circuit to be able to accommodate this.

For the small business owner, whose dependence on IT is no less valid than major data centre operators this leads to a dilemma, as he needs critical load power protection, but doesn’t have the infrastructure or budget to put in a fully configured n+1 solution.

The answer – the KTS redundant switch from Kehua. This is a rackmounted device occupying no more than 1U of height. It accepts two inputs and provides a single power output that is provided from a primary source. If the primary source should fail, the system will automatically transition to the secondary source within 4 mseconds which is fast enough not to be noticed by any computer type loads.

The primary source should be an online UPS system, and the secondary source can either be another UPS (for full protection) or fed from the mains so you can cover in case anything untoward should happen to the UPS. Of course, there is still the single point of failure on the KTS, but built with reliability in mind it has extremely high MTBF to ensure peace of mind.

Coupled with a KR1000J online double conversion 2U rack mount UPS, you can have a redundant solution for under £350, protecting up to 4 servers and occupying only 3U of rack space. Available in 2KVA, 3KVA and 6KVA modules the KTS redundant switch is an ideal method of achieving redundancy without breaking the bank.

KTS Redundancy Switch Available in 10A, 16A and 32A versions

If you’re a retailer, then Christmas is probably your busiest time of the year. The tills are (hopefully) in constant use taking cash, processing credit cards and printing receipts. What would happen if you were to experience a power glitch during your peak trading times and you lost your tills, lost the data, and customers decided to go elsewhere whilst they were waiting for you to reboot (hopefully) and get the systems up and running again. I bet the cost of such problems could run into far more than the £45 or so it costs to buy an ideal system to protect against such problems.

We’ve got the IP-PRO-Evolution at under £45 delivered. This will provide you with quality surge protection as well as battery backup allowing you to continue to trade even if the lights go off for a while.

If you’re short of space then what about the OPTI VS575C for £50 delivered? This is an ideal system for a EPOS terminal.

When money’s tight it’s easy to skimp on the power protection and not spend the money, but at these low prices it’s crazy not to.

If you are in need of power distribution in your data cabinet then look no further than the superb Eaton range of ePDU’s. With over 800 separate models with a variety if input and output terminations there’s a model that will be exactly what you are looking for.

With a choice of technology from Basic (just the electrical connections) to Metered and fully managed switched power distribution that can be monitored over a network, the Eaton ePDU range has it all.

In order to make your choice easier, there is a useful eDPU selection tool available to help. See http://eaton.powerinspired.com

We’ve recently sat down with our suppliers and negotiated new rates for our postage charges and we are pleased to say that prices are down across the board!

Smaller items will now be despatched through the post rather than courier slashing these costs, and we’ve now got a two tier upto 10Kg for only £8.05 and upto 30kg for only £11.50. All shipping charges are now detailed on the individual product pages so there are no surprises when you place your order.

While we’re on the subject we’re often asked why we don’t offer free shipping. Well that’s because shipping is never free. Anything with free shipping has the costs already incorporated into the price. So if you order more than one item you’re losing out as the items are usually combined into one delivery which is what we regularly do. For example, if you order a UPS from us and some additional power leads, the postage charge will be the same for the UPS with or without the leads. If we offered free shipping this wouldn’t be the case.

Remember we’re the most competitive UPS Systems store you will find anywhere.

Here’s a nice article extolling the use of online double conversion UPS Systems for hospital laboratory applications: 

http://www.laboratoryequipment.com/article-sh-reliable-test-results-1009.aspx

We couldn’t agree more.

Laboratory Equipment needs clean power to operate effectively, and this comes from  being supplied by a good quality sine-wave power waveform at all times. If you actually read through on the article above you will see an image of a “standard generator output”. Don’t be fooled by this.  Generators are never as bad as this – ever. However there is a degree of switching transients, power glitches and frequency variations that can cause havoc with lab equipment (so much so that I’ve known hospital labs to routinely unplug equipment during generator testing – so what will they do when the generator kicks in for real?). Depending upon the generator used and connected loads, the output from the generator can become distorted however, and this is where the online UPS will correct this. Other technologies cannot. I include in this galvanically isolated products that are based on line interactive technology. They cannot do anything about distorted waveforms except drop to battery and go dead a few minutes later.

Another issue that is technically incorrect is the use of galvanic isolation to correct stray earth currents. Since in most galvanically isolated equipment the earth is connected straight through, any current that is flowing will still flow, if the load is galvanically isolated or not. What galvanic isolation does do, is remove any neutral-earth voltage that may exist if the electrical infrastructure is poor or the line is long with heavy load equipment sharing it.

Our recommendations therefore, are for online double conversion for all laboratory products and there’s no need for galvanic isolation meaning smaller, lighter and ultimately cheaper products can be used instead.

I’ve mentioned in other posts that runtime is battery. On our websites we use calculated values to determine the runtime based on a particular load. The purpose of this post is to give you an understanding of this process.

The first thing you need to know is that battery discharge is non-linear. For those of you who don’t understand the expression I’ll elaborate. A linear expression is one where, for example, you put two in, you get four out. So it follows that if you put three in, you get six out, or you put five in, you get ten out. EG. whatever you put in  you get twice out. In the non-linear world this doesn’t hold true, for example, you put two in, you get four out, but when you put three in, you get nine out etc.. This non-linearity makes the discharge characteristics very difficult to express mathematically.

Luckily, the battery manufacturers provide us with discharge tables that we can look up, but first we need to know some information about the UPS, the load and about the method.

End of Discharge Point

At what point will the UPS switch off? Your normal 12V lead acid battery contains 6 cells each of a nominal voltage of 2V (so you get 6×2V=12V). In practice the voltage is slightly higher than this and reduces as the battery is discharged. It is important not to allow the battery to become too discharged, so the UPS will monitor the cell voltage and cut off when it gets to a predetermined point. This is usually around 1.7V per cell or 10.2V for 12V battery.

UPS Efficiency?

Well, more precisely, the inverter efficiency. The inverter is used to convert the battery DC power into AC power. There will be losses associated with this. The better the inverter, the lower these losses are. If you’re unsure, use a worst case of say, 80% efficient. This means that for every 100W provided to the load, the batteries will need to provide 125W (simply 100/efficiency).

The Load Power Factor

Is the load purely resistive, or does it have a power factor? We’re only interested in the amount of WATTS that are needed.

Amps or Watts Method?

Firstly, there are two methods for calculating runtime, the Amps method, or the Watts per Cell Method. Generally, Watts per Cell is used for short term discharges and Amps is used for long term discharges.

Process

It’s easier to do this with an example, so let us take a standard server type load with a number of ancillary devices. We know from measurement  that the Ampere draw is 7Amps and we have mains voltage of 235V. Our Watts therefore (assuming unity power factor) is 1645W.

Our UPS has an inverter that is rated at 90% efficient, so the amount of power from the battery required to deliver 1645W is 1645/0.9 = 1828Watts.

Our UPS is a 3KVA, 2.1KW UPS that contains 8 batteries connected in series. Each battery is rated at 12V 7.2 Ah.

 I now need to look up the manufacturers data sheet and I find the following for a 7.2Ah battery:

Constant Power Discharge Method 

Our battery load is 1828W and we have 6×8=48 cells. Therefore our Watts per Cell is 38Wpc.

We know the FV (Final Value or End Of Discharge Point) is 1.7Vpc so looking along the Constant Power Discharge Table, we can see that 52Wpc would give 5 minutes, so we will get more than 5 minutes runtime. We can see that 35.16Wpc would give 10 minutes runtime, so we will get less than this.

So the calculated runtime for this example, based on constant power discharge is between 5 and 10 minutes.

 Constant Current Discharge Method

We have a total of 8×12V batteries in series, giving us a string voltage of 96V. We need to deliver 1828W so our Amperage is 1828/96 (from Power=VoltsxAmps, so Amps=Power/Volts). = 19Amps.

Now looking along the table above in the Constant Current Section, with our FV of 1.7, we see that a 26A discharge would give us 5 minutes, so we will get longer than this. A 17.6Amp discharge would give 10 minutes, so we will get less than this.

Therefore using the constant current discharge method we will get between 5 and 10 minutes runtime.

Working it out in reverse – I want 2 hours runtime – how many batteries do I need?

Using Watts Per Cell Method.

From the table under Constant Power Discharge, we can see that for our FV of 1.7, for a 2 hour runtime we need to have a WPC discharge of no more than 6.05. Our load is 1828W, so we need 1828/6.05 = 302 cells, which is 50.35 batteries. The battery requires a 96V string voltage, based on banks of 8, so we will require 6 banks to get close (that is 48 batteries), or 7 banks to be sure (that is 56 batteries).

Using Constant Current Method.

From the table above under Constant Current Discharge, you can see for our FV of 1.7V we need to have no more than a 3.05A discharge from each of our batteries to achieve a 2 hour runtime.

Our total current draw is 1828/96 = 19Amps (1828Watts load/Battery String Voltage = 96V)

Dividing the 19Amps total current by 3.05 gives us the number of strings needed to achieve 2 hours runtime which is 6.24. Obviously we cannot add in a quarter of a string so we need to round up. In this case we require 7 battery strings, or a total of 56 batteries to achieve a runtime of 2 hours.

Alternatively, you could of course opt for higher capacity batteries, and maintain the same number of batteries. The examples above were using 7.2Ah lead acid batteries but there are other choices available.

Everybody is aware that a sudden loss of power to your PC will result in it switching off and you losing all data that you have accumulated since your last save. Even if the power cut is momentary, this is enough to cause a reboot.

This is bad enough for many people, especially when used for work and you’ve just lost all the data on that report you’d been writing. But did you know that mains fluctuations can cause damage to your hard drive?

A common effect is to hear a repetitious clicking noise coming from your hard drive – the click of death (like the blue screen of death but more fatal if there’s such an analogy). This renders your hard disk inoperable. What does this mean?

Well, your PC cannot function. You cannot access any data that you have on it without specialist services, and you need to replace your Hard Disk Drive (HDD), it cannot be repaired.

The cost of a new hard drive is relatively cheap these days. Probably around the £30 for a no-frills device. But then you have to fit it, and reload all your software. Assuming you’ve got all the CDs/DVD’s, and your access codes for downloaded software, plus you backed up all your important memories from your digital camera (you did didn’t you?), then this should be a breeze. Only taking a full day or so. It’s no laughing matter loading a PC from scratch. You get used to all your settings, software, and although sometimes its good to have a purge you’ll be surprised how long this process can take.

If you needed to recover data from your hard drive, well that’s a different story. You will be charged anywhere upwards of several hundred pounds to have data recovered – if it can be recovered.

To avoid these issues you need to invest in an Uninterruptible Power Supply. These will allow you to work through brief power cuts and shut your computer down (after saving your work), if the outage is longer than a few minutes. Some people provide a degree of power protection for their PC’s by using surge suppressors. Note that these will NOT protect damage to your HDD because of power fluctuations. A surge strip can do nothing to protect against mains voltage variations and power cuts.

How much is an Uninterruptible Power Supply? It depends upon the level of protection you require and the amount of runtime you need, but a basic standard system can be bought for under £30 (plus VAT). Power Inspired’s VIX series Uninterruptible Power Supply fits the bill for a home office / small office PC and is such a low cost it’s a no-brainer to me.

Professor Mackay, the governments new energy advisor is predicting rolling blackouts for the UK according to this article. Good news for those in the Uninterruptible Power Supply industry then?

Most UPS Systems designed for home use or the small office are there to protect against momentary outages up to and around 10 minutes or so. If you want power during an extended outage you will either require a lot of batteries or move to a generator of some description. You will also need to determine what exactly it is you wish to protect. For example, do you want to protect individual pieces of equipment – thereby needing a UPS per piece unless they are close to each other. Or do you want to protect everything on the same circuit – in which case you will need to connect the UPS into your existing electrical infrastructure.

The advantages of a UPS over a generator is that the UPS can be located indoors, whereas a generator needs venting and so is best placed outdoors, but in either case you may need some electrical wiring done.

We’ll shortly be introducing a range of UPS Systems to power entire homes or just circuits that are ideal for long run time applications. They are wall-mounted and have extra large chargers for maintaining a large battery bank. They also have some very neat features that you will be amazed by, but I’m not ready to tell you yet. Watch this space…..

As our product range has expanded we’ve come to realise that we may be confusing everybody with the wide choice of different systems we have available. What we’ve done is to streamline the UPSMart shop and also provide a new outlet at www.powerinspired.com, where all products will be available. UPSMart is now dedicated to home and small office users. Power Inspired will deal with the professional users. We hope this will help streamline our online product offering.

The following product categories are no longer available at UPSMart but are at Power Inspired:

• Medical UPS Systems
• Three Phase UPS Systems
• Marine UPS Systems
• UPS Systems over 3KVA
• Power Conditioners and Power Conditioned UPS Systems
• Eaton Online Double Conversion UPS Systems

In addition some products have been removed in their entirety. Links are provided for legacy reasons. Any link into the UPSMart website will provide the appropriate link for the Power Inspired website if the product has been removed from UPSMart.