Dairy producer reduces refrigeration energy use

The solution, which also features a Leroy-Somer Powerdrive high-power modular drive, is being used in an industrial refrigeration system that cools milk after pasteurisation or sterilisation. Based near Ghent, Inex specialises in products including milk, chocolate milk, buttermilk, fermented milk, yoghurt, cream and butter.

Founded in 1898, the company manufactures and packages both fresh and long-life produce for large European retail chains and multinationals. It has around 440 employees and annual sales of circa €150m.

Since refrigeration is a key element in the manufacturing process, optimum operation and reliability is paramount. As part of a recent investment package, Inex acquired four new industrial refrigerator systems based on Sabroe SMC 106E reciprocating ammonia compressors. At the time, the company had heard good reports of permanent magnet motors and wanted to install one as a trial

As a result, three of the compressors were supplied with standard Leroy-Somer IE2 (90kW) asynchronous AC motors, and one with a Leroy-Somer IE4 (105kW) synchronous permanent magnet motor from the Dyneo range. 

The refrigeration systems are used to cool water to 1°C, which in turns cools milk to around 4°C. The installation operates almost continuously, but at variable load. Here, the benefits of permanent magnet motors come to the fore as their performance retains almost constant partial load, unlike standard asynchronous motors, generally leading to a reduction in energy consumption.

To put the theory to the test, Control Techniques and Leroy-Somer’s experts visited Inex after the installation was complete. They discovered that the refrigerator operating with the Dyneo permanent magnet motor was delivering significant energy savings.

Using a digital energy analyser, the drive and motor experts made a series of power measurements comparing two refrigeration units working at the same conditions. One featured the LSRPM280SC-T synchronous magnet motor (105kW) running at 1,500rpm and Leroy-Somer Powerdrive, while the other housed the standard LSES280MK-T (90kW) asynchronous motor running at 1487rpm and a competitor drive.

It was found that energy savings were being achieved using the permanent magnet motor across a range of different load profiles. Depending on the type of measure, involving number of pistons, speed, evaporation temperature and condensation temperature, the calculated energy savings were between 18-21%, taking into account any losses from the drive and the motor.