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AC motors and low-voltage AC drives from ABB are expected to help Alma Products, a supplier of extruded plastic products for food applications, to reduce its annual electricity bill by GBP80,000.

The company had been facing rising electricity costs that threatened to make it less competitive.

David Green, engineer manager at Alma, asked ABB motor service partner Quantum Controls to look at the energy usage of its extruders and to recommend options for cutting the company’s energy consumption.

The extruders were running in a DC drive system that drew a load whether it was required or not, because DC motors draw a current even while producing zero torque.

The maintenance cost of the DC motors was also an issue, as it far outweighed the AC motor option.

As the project was proposed for Carbon Trust funding, a precise energy-save reduction had be obtained for converting from DC to AC on the extruder lines.

Alma obtained two estimates from other manufacturers, which offered a savings difference of nearly GBP60,000 per annum between them.

Quantum was approached for advice and a hire trial was proposed to prove the savings before committing to a purchase and the Carbon Trust funding.

One of the DC systems was monitored by Quantum over a two-week period with a three-phase energy data logger on the input supply to the DC system.

Quantum then fitted a temporary ABB 132kW AC drive and an ABB 132kW motor and monitored the system for a further two weeks for comparison purposes.

The test results showed that the AC drive had saved just more than 25 per cent of consumed energy compared with that of the DC drive system.

This would give an estimated total saving of more than GBP80,000 when all four main extrusion lines were converted to AC drives.

’We recommended an AC drive in place of the DC drive as it would give maintenance savings and energy savings, as the AC drive system is more efficient than that of the DC,’ said Quantum’s Peter Stelling.

Following the tests, Quantum was awarded the contract to fit motors and drives on all four extruders.

The project was funded by a GBP100,000 loan from the Carbon Trust.

The drives are fed from 4-20mA signals from pressure transducers before and after the extruder pump.

The signals enable speed control in order to maintain the correct back pressure.

This ensures that the correct amount of material is being fed to the extruder and that there is no danger of overpressures causing damage to the machine.

Overall, Green expects a two-year payback on the project.

’There is another potential benefit of the drives installation, in that it gives us more information on what is happening with the process.

’In time, this will help us to calculate throughput and gives us a better idea of the load the machine is handling and how efficiently we are making use of its production capacity,’ he said.

ABB Automation Tech – Drives and Motors

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