We Supply and Install and maintain a large range of Generators. We only supply generators from the Industry leaders. We supply for all your requirements with product ranges from 5 – 3000kVA.

Our range includes open and enclosed generator sets which are diesel powered.


At Fables Power Solutions (FPS) we have a range of robust Single Phase and Three Generator Systems rated from 1KVA upto 5MVA.

Whilst many UPS system and power protection providers are tied to a single manufacturer of engines or alternators, at FPS we are completely independent. This means that we can select each set and system to match your exacting requirements and your allocated budget, without any limitation on choice. We will always provide a ‘best fit’ solution without compromising on quality or engineering resource.


The generators and range of power protection products that we offer cater for a wide variety of situations. We do not simply offer generators for sale – we offer comprehensive solutions. So whether you require sets and systems suitable for residential use, or require an all-inclusive solution fit for full industrial applications with prime power or emergency backup requirements, we are able to comply.

With many years of experience in the Emergency Power Industry, Fables Power Solutions have offered peace of mind for many businesses and users alike, with the means to maintain, protect and power critical operations for data centres, hospitals, emergency services, universities, marine and military services and more.

Matching a Generator to Your UPS

When specifying a UPS system, Generators are not always included. However if a Generator is on site or a decision has been made to add a Generator onto the UPS it is extremely important that the Generator and UPS are perfectly matched.

Firstly why would I need a Generator with a UPS?

Standby generators are installed to supply power during lengthy power outages. A UPS normally has battery backup from 5 minutes to a few hours depending on site and purchase. The Generator will extend this power for several hours or indeed several days if required.

The Generator power is routed through the UPS system to maintain extended runtimes to the critical systems attached to the UPS.

This not only removes the need for an orderly shutdown when batteries are low as they will never get low but also means that as long as there is power being generated from the Generator output the critical systems attached will always get pure sine wave power through the UPS (assuming true on line double conversion). In short the Generator will maintain the power supply to the essential systems during a protracted loss of mains power.

10 times out of 10 to cater for extended runtimes, most sites will always choose a generator alongside a UPS system. The Generator as explained above will maintain power for as long as there is fuel. Refuelling is required and dependent on the tank size of the generator.

These typically being from 4 hours to 24 hours. Likewise it is dependent on how much power is being drawn and the efficiency of the UPS system.

Therefore in critical applications such as banks, hospitals, police, MOD, emergency services, Universities, a standby power generator is as important as a UPS; it can be the only practical source of power during an extended power failure situation.


If I have a Generator Why do I need a UPS?

If mains power fails, your UPS will accept the load and support the connected equipment. The Generator as explained above is there to add extended autonomy / runtime in the event of a power failure. If a Generator alone is connected to equipment and not via the UPS system the following might occur:-

Break in Power

Small Break in Power from when the Generator starts up and when it is providing suitable power. This can range from a few Milliseconds to several minutes in older Generator sets. So the UPS is in short providing back up power while the Generator gets up to speed.

Unacceptable frequency ranges

Consistent voltage and frequency are directly proportional to the size and type of generator on site and installed. Small IT type of Standby generators are typically smaller than fully rated generators that would support equipment within other areas of a building, a complete building or manufacturing facilities.

These smaller types of generators produce less consistent power with voltage and frequency fluctuations. However when the voltage range may be acceptable, the frequency range can often be wider than off-line or line-interactive UPS are designed to accept.

As a result it is almost impossible to make an off-line or a line-interactive UPS work with a standby generator. However True On Line double conversion systems do.

Off-line and line-interactive UPS technology

In Off line, Standby and Line Interactive UPS systems the UPS passes mains power to the load. Some off-line and Line Interactive UPS systems may have some surge suppression and filtering, but will have no true power conditioning like a True On Line Double Conversion UPS system will have.

However  line-interactive UPS systems have some power conditioning functions, but focus entirely on correcting voltage variations by means of a transformer and an automatic tap-switching feature. This in effect has no effect on frequency variations to this means that the UPS system will react to out of specification frequencies the exact same way as off line UPS systems.

When the batteries are depleted in both systems this will shut down the UPS system and therefore drop the load, which is obviously not the best scenario.

Why True on-line Double Conversion UPS technology works best with generators

FPS supply UPS systems that are using True On-line Double conversion technology which are ideal and perfect for use with Generators. Our range of True on Line UPS systems are ideal for use with generators as they accept high input power with relatively wide variations in voltages and frequency variations.

The UPS systems we supply and provide an output waveform that is pure sine wave. In our systems the AC input from either the mains or a standby generator is first converted to DC by the rectifier. The DC current is used to charge the battery. During an outage, DC current from the batteries is reformed by an inverter back to pure sine-wave AC for the critical load. In some of our systems we also include Power Factor correction to provide an even wider input voltage range.

FPS True On Line Double conversion units are true on line double conversion (AC to DC / DC to AC). Therefore variations in the input frequency are of no real concern. On this basis, the same frequency variations that would cause an off-line or a line-interactive UPS to transfer to battery power have no effect on FPS range of True on-line double conversion UPS systems.


Sizing the generator

When sizing a Generator the Generator must be sized suitably adequate for the UPS system it is supplying. As well as being capable of handling the step load of the UPS, the generator must have sufficient capacity to charge / recharge the UPS batteries and cover the conversion losses of the UPS. For example systems are not 100% efficient.

The maximum step load of most generators is around 65% of the total rated capacity of the generator. Conversion losses and charging current can add a further 15% to the rated UPS power draw.

A 100kVA UPS can therefore draw 115kVA and to accommodate a step load of the generator this must be sized at typically 175KVA or 75% larger than the UPS. However on Fables Power Solutions’ IGBT based UPS systems we can use a lower figure typically 25% larger Generator due to the way this draws power. For example on the Boxer UPS 100KVA you can use a 125KVA Generator.

This will save money on Generator hardware as well as running costs. For further details please contact Fables Power Solutions.

In a current datacenter sometimes air conditioning is connected to the UPS, likewise it is strongly recommended that the batteries and UPS are in an air conditioned environment to get optimum use of UPS and enhance lifetime of batteries.

However instead it is better to support it on the generator (because the Air con can handle a break in power while the generator starts) The load can then be timed to reconnect once the step load of the UPS is supported, making full use of the generator capacity and likewise UPS capability.

Running temperature

Another reason to add further capacity on the Generator set is that when running it is quite normal to experience a rise in temperature within the close area of the generator.

When exposed to high ambient temperatures the Generator will not be running efficiently, it is then there will be losses on the output power.

High running temperatures will also cause damage to both the turbo charger and exhaust system. If this is likely it is suggested and put into practice that you increase the overall size of the generator installation. A generator will run cooler when not working to its full capacity.

Load the generator to 75% of its overall capacity for constant running. There is no problem with running a standby generator at 100% of its output capability for short periods, however most generators are not generally designed for this. A ‘prime power’ generator should be specified where this is likely.

Rating Definitions

Prime Power

These ratings are applicable for supplying continuous electrical power (at variable load) in the lieu of commercially purchased power. There is no limitation to the annual hours of operation and this model can supply 10% overload power for 1 hour in any 12 hour period.

Standby Power

These ratings are applicable for supplying continuous electrical power (at variable load) in the event of a utility power failure. No overload is permitted on these ratings. The generator itself should be equipped with a good electronic governor. This will reduce the magnitude of frequency deviations on its output. There should also be an automatic transfer switch, ahead of the generator, which should have an in-phase monitor.

The load transfer switch prevents the generator power from back-feeding the mains supply. An in-phase monitor ensures that the two power sources (generator and mains power) are not out of synchronisation when mains is restored as the transfer switch cuts away from the generator in favour of mains. Out-of-sync power sources could result in a potentially destructive power spike to the UPS and unprotected connected equipment.


In summary, a matched UPS and generator for mission-critical applications requires a True On Line Double Conversion UPS system that can accommodate variations in frequency and input voltages. There should also be an adequately sized generator that will absorb various voltage variations. Further governance can be provided by an electronic governor on the generator and an in-phase monitor on the ATS (automatic Transfer Switch).


Please see our parnerships below.




SDMO® Industries

Established in 1966, SDMO® Industries, based in Brest, Brittany is now the leader in France and the third largest manufacturer worldwide of generating sets. The company designs, manufacturers and markets a range of standard generators from 1 to 3300Kva to meet all power needs and to suit all applications. The company has grown and developed through its philosophy that strives for product improvement and innovation.


View our SDMO Product Range:





ComAp specializes in creating electronic control and management solutions for use in the power generation industries and drive power markets. Our portfolio of products, software and accessories is designed to support emergency power, standby power generation and engine driven applications all over the world.

ComAp is a dynamic international company with a solid reputation for delivering innovative electronic solutions to the power generation, industrial engine and equipment market. By providing customers with state-of-the-art products, ComAp has built a name for delivering excellent reliability and good value.Customer satisfaction is our mission. We continuously develop our people to be the best to succeed in our mission.

The history of ComAp goes back to the last century when Libor Mertl and Ales Prochazka, two electronic engineers, left the Engine Research Institute in Prague and on March 1st, 1991 established the Computer Applications Company – ComAp.




Deep Sea Electronics is one of the world’s top manufacturers of generator control, auto transfer switch and battery charger equipment. They employ over 120 people on four continents and sell our products to 150 countries direct from our UK head office and through our comprehensive distributor network.

Throughout their 40-year history, they have invested heavily in people, processes and research & development to ensure DSE continues to enhance its reputation across world markets.

DSE has UK manufacturing and engineering facilities to be proud of. They develop and manufacture a range of over 140 different products that provide flexible control solutions for multiple applications.





Perkins Engines (officially Perkins Engines Company Limited), a subsidiary of Caterpillar Inc., is primarily a diesel engine manufacturer for several markets including Agricultural, Construction, Material Handling, Power Generation and Industrial.It was established in Peterborough in 1932. Over the years Perkins has expanded its engine ranges and produces thousands of different engine specifications including diesel and gas engines.




Volvo Penta was founded in 1907 in conjunction with the production of the first marine engine, B1. The Penta company soon became an established internal combustion engine manufacturer, which in 1927 delivered the engine for Volvo’s first passenger car.

Volvo acquired Penta in 1935 and Volvo Penta has been part of the Volvo Group since then. It now provides internal combustion engines (ICEs) and complete power systems to the boating industry, power-generating equipment, and similar industrial applications. The business also manufacturers sterndrive and inboard drive systems such as the Volvo Penta IPS.[1] The engine programme comprises petroleum fuel (diesel and petrol) engines with power outputs of between 7.5 and 1,500 kilowatts (10 and 2,039 PS; 10 and 2,012 bhp).





Since its founding in 1837, John Deere has seen a great many changes in its business, its products, its services.
In 1837, John Deere, blacksmith and inventor, had little more than a blacksmith shop, a piece of discarded polished steel, and an idea that would help farmers, changing the face of agriculture for all time.The quality of a company is expressed through the quality of its leadership. For nearly 175 years, John Deere has benefitted by strong, decisive leaders at its helm, dedicated to the core principles of integrity, quality, commitment and innovation.
One of the world’s most recognized corporate logos, the leaping deer trademark has been a symbol of quality John Deere products for more than 135 years.


About MTU UK

Since 1986, MTU’s main central is supply of premium class diesel and gas engines and systems to the Marine, Power Generation and Rail markets. In April 2008 the business relocated to new purpose-built premises in East Grinstead, West Sussex.

They have built their first-rate reputation on an outstanding in-house product, excellent customer service levels and strong customer relations. These values have contributed to their considerable growth and success in all competitive markets.

Their head office, MTU Friedrichshafen, located in Germany, is the manufacturing hub of series 2000 to the 4000 for both Marine and Power Generation applications. Other products and functions are based elsewhere in Germany and the World. Their company was founded in 1909 and has since become the leader in innovation and performance, giving them a wealth of experience in a vast range of applications.