Some synchronous reluctance motors are being sold as having IE6 efficiencies even though is no official standard yet for this level of efficiency
Some motor manufacturers are already offering “IE6” machines, even though no official standard yet exists for this level of efficiency. Daniel Eberli, head of IEC LV motor product management at ABB, explains how and why this is happening. water impeller
IE6 hyper-efficiency is the latest buzz in the electric motors industry. Some manufacturers have already announced models based on various technologies that meet this anticipated level of energy efficiency. The puzzle for customers is understanding what IE6 really means when IE5 is currently the highest official standard defined by the IEC (in TS 60034-30-2:2016).
The standard allows direct comparison at the IE class level of traditional induction motors in variable-speed uses with advanced technology motors designed only for VSD (variable-speed drive) operation – such as synchronous reluctance (SynRM) machines. It does not matter if the IE classification is done with a DOL (direct-on-line) supply, in accordance with IEC 60034-30-1, or with a VSD supply, in accordance with IEC TS 60034-30-2, because the given IE class still characterises the efficiency performance of either approach in VSD operation. This makes it clear for customers that motors in the same IE class have the same minimum efficiency performance.
What is happening now is that the speed of development in energy-efficient motor technologies has outstripped the evolution of standards to define it. In fact, in many cases, when working on high-end applications, we find that customers tend to ask for the highest level of energy efficiency possible, rather than asking for a motor to meet a specific IE class.
Even so, we need a common language across the industry, and that must be underpinned by common standards to bring clarity to all stakeholders – users, regulators and manufacturers. The challenge is that IE6 does not yet have a rigorous definition.
ABB’s philosophy is to operate on the basis that, so far, each higher IE efficiency class has had 20% lower energy losses than the previous one. This “20% principle” is generally well-known in the market. Therefore, we define IE6 as offering 20% energy lower losses than IE5.
However, while we have our own interpretation of IE6, our view, in common with other major manufacturers, is that standards play an important role in driving energy efficiency forward. That is why we are committed to working together with the relevant industrial bodies to ensure that IE6 is defined and adopted officially, even though this could take some time to happen.
Various motor technologies can be used to achieve IE6 performance, but no single technology can meet all application needs. ABB’s approach is, therefore, to offer a full technology portfolio so we can always supply the most competitive motors for the specific requirement. Among the possible solutions in ABB’s portfolio are SynRM motors, permanent magnet (PM) machines, and a hybrid SynRM-PM technology (known as PMaSynRM ) that was launched in 2014. It gives the SynRM design a permanent magnet “boost”.
An advantage of PM motors for achieving high efficiencies is that their magnets create the essential magnetic field without needing current in the rotor. This reduces copper losses compared to induction motors. However, there are challenges regarding potential de-magnetisation, complicated maintenance and price fluctuations associated with the use of magnets. Furthermore, the most powerful magnets typically use rare-earth elements (REEs) such as neodymium and dysprosium. These are both expensive and geo-politically sensitive, while REE mining and production is often not environmentally sustainable.
Therefore, while staying open-minded about energy-efficient motor technologies, we believe that the magnet-free SynRM design currently offers the best combination of performance, sustainability, simplicity and service-friendliness.
Externally, a SynRM motor looks similar to a traditional induction motor. Even the internal stator is traditional. The innovation is in the rotor, which is made from laminated iron layers that form a light, but solid, construction that allows magnetism to flow through it. The shape is designed to guide magnetic reluctance within the rotor. As a result, the rotor will align itself to the magnetic flux produced by the stator coils, essentially “locking” into position. This allows it to move at exactly the same speed as the magnetic flux – synchronously – hence the name, synchronous reluctance motor.
SynRM motors must be paired with a matching VSD to operate. This package is the ideal upgrade, especially as the motors are the same frame size as equivalent IE3 induction motors, making it easy to replace legacy motors with modern, high-efficiency products.
Earlier this year, ABB become the world’s first manufacturer to offer a magnet-free motor designed to comply with the anticipated IE6 standard. This was achieved by adopting more accurate tools that enabled us to design an IE6 SynRM by adjusting the combination of several motor parameters, such as length, grade of material, and windings. A key requirement was not to alter the frame size, thus ensuring that the new motor remains a drop-in alternative to an equivalent induction motor.
It is understandable that users are reluctant to make an additional investment in IE6 motors that meet an anticipated standard when an IE4 motor will comply with current European Union Ecodesign legislation. However, it is the role of our industry to give them all of the information they need to help them look beyond the upfront investment and to consider the total cost of ownership (TCO) of a motor. For an IE6 SynRM machine, the upfront cost is a typical average of around 2% of its TCO. Maintenance accounts for 1%, and the remaining 97% is spent on electricity.
As a practical example, consider a 55kW motor application running for 6,500 hours a year at 75% power, on energy costing €0.2/kWh. In this scenario, upgrading from an IE3 motor and VSD package to an IE6 SynRM package yields annual cost savings of €1,772 and CO2 savings of 2,685kg. Over a service life of 25 years, this will deliver a total saving of €44,295, while eliminating 66,000kg of CO2.
intelligent pump IE6 hyper-efficiency motors are commercially available here and now, even while we wait for an official standard. For most industrial applications, magnet-free SynRM is a great all-round IE6 technology in terms of energy efficiency, power density, compact size, resource usage and maintenance needs.