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E.ON, a UK power and gas company, has installed two large motors from WEG Electric Motors at its Ratcliffe-on-Soar power station near Nottingham.

Both motors have been installed in the flue gas desulphurisation (FGD) plant, which helps to reduce SO2 emissions, while also creating commercial-quality gypsum.

The main criteria when sourcing the motors were energy efficiency and reduced maintenance requirements.

Chris Bennett, a senior electrical engineer at Ratcliffe, said: ‘It is always surprising to people who visit the site that we are so efficiency conscious, but they’re often even more surprised that we have to pay for the power we use during the generation process, so it’s essential we don’t use more energy than we actually need.

‘Even more important is minimising the environmental impact of the power station and ensuring the reliability of the plant; outages have to be avoided where possible, so critical equipment such as the motors have to be reliable.’ The first motor to be installed was a 6,150kW, 10-pole, 11kV WEG M-line MGF 1000 unit, which is being used to drive the booster fan on the FGD plant.

The motor is an IEC 1000 frame size with an output torque of more than 100,000Nm.

It is the largest of the WEG motors currently installed at the power station.

The booster fan is used to power the flue gas through the FGD plant.

The second motor, also an MGF high-voltage unit from WEG’s M-Line of high-voltage motors, is a smaller IEC 400 frame size MGF 400E 750kW, four-pole 3.3kV motor.

This motor drives an absorber recirculation pump on one of the FGD towers.

These pumps are used to transfer up to 8,000 tonnes of limestone slurry an hour to the top of the 50m-high towers to be sprayed into the flue gas.

The 700-acre Ratcliffe site has a generation capacity of 2,000MW from four 500MW units – enough to meet the needs of approximately 1.5 million homes.

The power station’s desulphurisation process passes flue gas through a heat exchanger to cool it to less than 90C.

The gas is then drawn into the tower where it comes into contact with the limestone slurry.

This creates a chemical reaction, removing the SO2 and converting the limestone into calcium sulphite, which is, in turn, processed to create commercial-quality gypsum; during the process, 95 per cent of the hydrogen chloride is also removed.

Once the SO2 has been removed, the gas is reheated to allow it to rise through the chimney.

The motors must be able to survive in an outside environment for a long period, working at a continuously high load.

WEG motors are said to be suitable as they are reliable and safe in arduous operating environments.

The motors are designed to be compact and robust, featuring cast-iron frames, corrosion-resistant finishing and galvanised mounting components.

The windings are sealed using a vacuum pressure impregnation (VPI) system, which is claimed to guarantee high-quality insulation and stator coil protection through the application of a special epoxy-based resin.

The WEG units employ a combination of an internal cooling circuit, external cooling fins and high-efficiency cooling fans to ensure an optimum temperature gradient within the motor.

Coupled with specifically dimensioned high-quality bearings, these ensure that the motors have a long running life, according to the company.

WEG motors have dynamic balancing at motor operating speeds.

In this case, the standard balancing is on two planes; WEG can provide three-plane balancing on request.

Both are computer controlled and are capable of very low vibration levels, extending both bearing and motor life.

As a result of their design, WEG motors require very little maintenance – other than lubrication – to keep them running efficiently.

WEG has employed a pressure grease relief system, which enables old grease to be removed and replenished while the motor is still running, reducing the need for maintenance downtime.

WEG Electric Motors

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