Drive systems: helping reduce the energy bill

Variable speed is the main way to achieve savings. Leroy-Somer and Control Techniques, now part of the Nidec group, have developed variable speed drive systems whose components are engineered to complement each other. Simple to install and straightforward to maintain, these solutions are said to be able to deliver energy savings and a quick return on investment in a range of processing applications.

The Leroy-Somer Dyneo range of synchronous permanent magnet drive solutions, for example, offer super premium efficiency levels exceeding IE4 classification. By reducing rotor losses, its radial magnet rotor technology improves drive efficiency and specific output power. At rated speed, LSRPM motors in the Dyneo range are said to have better efficiency than high-efficiency induction motors. This difference in efficiency becomes more significant when operating below rated speed – which is by definition the case in variable speed applications. For this reason, Dyneo solutions using Powerdrive MD2 variable speed drives are particularly suited to use in refrigeration compressor applications, where the need varies according to the season and production rates.

A Belgian producer of dairy products is achieving minimum energy savings of at least 18% from its refrigeration process as a result of switching to Dyneo permanent magnet motor technology. The solution is being used in a commercial refrigeration system that cools milk after pasteurisation or sterilisation.

Refrigeration is a key element in the company’s manufacturing process, so optimum operation and reliability is paramount. The company had acquired four new commercial refrigerator systems and had heard good reports about permanent magnet motors and wanted to install one as a trial. So, 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.

Using a digital energy analyser, a series of power measurements compared two refrigeration units working at the same pressure. One featured the synchronous magnet motor (105kW) running at 1500 rpm and Leroy-Somer Powerdrive, while the other housed the standard (90kW) asynchronous motor running at 1487 rpm 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.