IE5 synchronous ­reluctance motors

IE5 synchronous ­reluctance motors

ABB IE5 synchronous reluctance motors (SynRMs) deliver ultra-premium energy efficiency – a new level of efficiency defined by the International Electrotechnical Commission (IEC) – and are the first choice to meet the growing global demand for improved energy efficiency.

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Tero Helpio ABB IEC LV Motors ­Division, Motion ­Business Area. Helsinki, Finland, tero.helpio@fi.abb.com; Jouni Ikäheimo ABB IEC LV Motors ­Division, Motion ­Business Area. Helsinki, Finland, jouni.ikaheimo@fi.abb.com

One-third of all electricity is converted into motion by electric motors and the number of such motors is expected to double by 2040, which is the equivalent of adding an electricity market the size of China to global power demand. This impending massive increase in the use of electrical energy is driving a need for more efficient motors.

01 ABB’s new IE5 SynRMs are ideal for applications such as water pumping.
01 ABB’s new IE5 SynRMs are ideal for applications such as water pumping.

The traditional induction motor (IM), though the most common electric motor in industry, has inherent drawbacks that arise from its asynchronous speed – such as rotor heating losses, which decrease efficiency and component and bearing lifetime. ABB’s new IE5 synchronous reluctance (SynRM) motors, however, deliver ultra-premium energy efficiency, which is a new level of efficiency defined by the IEC. The SynRM is characterized not only by its high energy efficiency but also by its reliability and low maintenance needs →01 – 02.

02 The IE5 SynRM represents a major step forward in sustainable electric motor tech­nology in terms of efficiency, reliability and power density
02 The IE5 SynRM represents a major step forward in sustainable electric motor tech­nology in terms of efficiency, reliability and power density

What is a SynRM?
SynRMs work on a very elegant principle that has been known for a long time, but only since the recent rise of sophisticated variable-speed drive (VSD) control has it been possible to exploit fully these super-efficient electrical machines.

In a SynRM, the rotor is designed to produce the smallest possible magnetic reluctance (the resistance to the flow of a magnetic field) in one direction and the highest reluctance in the direction perpendicular. The VSD steers the stator field so it “rotates” around the motor. The directionally unequal magnetic reluctance properties of the rotor cause the rotor to rotate with the field and at the same frequency.

SynRM technology combines the performance of the permanent magnet motor with the simplicity and service-friendliness of the induction motor, as SynRMs do not feature rare-earth-based components like permanent magnets. The rotor has neither magnets nor windings and suffers virtually no power losses. And because there are no magnetic forces in the rotor, maintenance is as straightforward as with induction motors.

ABB’s SynRM was launched in 2011 with an IE4 efficiency class, available at first for pumps and fans, and now available for all applications. ABB introduced the IE5 SynRM ultra-premium efficiency motor in 2019. ABB offers two ranges of SynRM:
• High-output SynRMs with an output of 1.1 to 350 kW in frame sizes IEC 90 to 315.
• IE5 SynRMs with an output of 5.5 to 315 kW in frame sizes IEC 132 to 315.

On the drive side, the number of VSD applications is increasing, helping the drive technology for SynRMs become more commercialized. Customers can increase their energy efficiency, improve sustainability and enhance reliability by upgrading to ABB IE5 ultra-premium SynRMs, which offer up to 50 percent lower energy losses compared to IE2 motors, as well as significantly lower energy consumption and CO₂ emissions than the commonly used IE2 IMs →03.

03 The IE5 SynRM improves performance in applications such as silo operation.
03 The IE5 SynRM improves performance in applications such as silo operation.

Lower temperatures and mechanical compatibility
SynRM technology offers up to 30 °C lower winding temperatures and up to 15 °C lower bearing temperatures. These lower operating temperatures have multiple benefits – including longer insulation life and longer bearing greasing intervals and lifetime. Lower bearing temperatures are an important factor because bearing failures cause about 70 percent of unplanned motor outages.

The IE5 SynRM is the same size as an IE2 induction motor, eliminating the need for mechanical modifications if upgrading, thus making replacement of the traditional induction motors easy. This compatibility also simplifies spare part provision and maintenance.

IE5 according to IEC TS 60034-30-2
The IEC 60034-30-1 technical standard for IE efficiency classification has now been superseded by IEC 60034-30-2:2016, which defines new efficiency classes of variable-speed AC motors that cover, for the first time, ABB IE5 SynRMs. It is from this standard that the “Ultra Premium Efficiency – UPE” classification that describes ABB’s SynRMs originates.

The new standard allows direct comparison at the IE class level of traditional induction motors in variable-speed usage with advanced technology motors designed only for VSD (like SynRMs). It does not matter if the IE classification is done with a direct on line (DOL) supply according to IEC 60034-30-1 or with a VSD supply according to IEC TS 60034-30-2 as the given IE class still characterizes the efficiency performance of either solution in VSD operation – ie, motors of the same IE class have the same efficiency performance.

To make a valid comparison, the IE class limit values in IEC 60034-30-2 are reduced by adding the additional harmonic losses in the DOL motor caused by the drive: 15 percent further losses for DOL motors up to 90 kW and 25 percent for DOL motors above 90 kW. For example, a 15 kW IE3 DOL motor of 92.1 percent nominal efficiency working with a VSD would have an actual efficiency of 91.0 percent (ie, 15 percent less). This is the value that must be compared against the 94.8 percent efficiency of an equivalent SynRM. Limit values are to be achieved at 90 percent speed and 100 percent torque. The ABB IE5 SynRM catalog includes a precalculation of the typical IE3 motor efficiency with a VSD to help make an easy comparison.

In practice, IE5 motors have 20 percent lower losses compared to an IE4 motor, regardless of the technology or IEC standard used.

Partial load efficiency
According to the new Regulation EU 2019/1781 (which lays down eco-design requirements for electric motors and VSDs) manufacturers need to state the losses at specified load points for a motor. This data enables motor-to-motor comparison under partial-load conditions on VSD duty. Traditionally, a comparison has not been possible due to the lack of loss information for IMs on VSD duty. IE5 SynRMs perform very well at partial load.

IE5 SynRM versus IE3 induction motors in VSD duty
ABB laboratory measurements have demonstrated the advantages of SynRM IE5 motors over IE3 motors, including under partial-load conditions, where the benefits are even more marked than at the nominal point. →04 shows the typical efficiency performance of an IE5 SynRM versus an IE3 induction motor in pump/fan duty according to ABB laboratory measurements.

04 Comparison of IE3 IM and IE5 SynRM efficiency at various pump or fan loads (laboratory measurements).
04 Comparison of IE3 IM and IE5 SynRM efficiency at various pump or fan loads (laboratory measurements).

Lower energy use results in lower total cost of ownership
Reducing energy consumption with SynRM and VSD packages means that the cost of running the process and the total cost of ownership will be reduced too. And, although companies can be reluctant to change motors or add drives to their processes due to the upfront investment costs, the cost of a motor is only a fraction of the cost of the energy used to run it.

Lifetime energy savings payback
For a 110 kW motor running at 1,500 rpm, the difference in initial cost price between an IE5 SynRM motor and an IE3 motor is negligible compared to the annual savings in energy costs. An IE5 motor package will save energy and costs compared to the IE3 package as soon as it is operational, paying back the cost difference after about 13 months. In addition, the IE5 SynRM package will continue to generate annual savings for the rest of its working life, which may be from 10 to 15 years. Within about 10 years, the savings generated through reduced energy use will have paid back the initial cost of the whole IE5 package.

Motoring into the future
Because IE5 SynRMs use less electricity than other motors, CO₂ emissions are reduced. Constant, quadratic torque with high efficiency delivers fast, precise control. ABB IE5 SynRMs deliver full torque from zero speed and give excellent partial-load efficiency →05. Speed control is very accurate due to the synchronous nature of the motor and there is almost servo-like performance due to low rotor inertia. The motor is very quiet and is ideal for driving pumps, fans, compressors, etc., in any industrial application. Numerous customer installations are already operating with ABB IE5 SynRMs to cut costs and boost productivity. One food processing company, for example, nearly halved the energy use of a fan system by switching to ABB SynRMs.

In motors, ABB prides itself on having the right solution for any industrial need and as a response to market demands for higher output, higher efficiency, longer service intervals and footprint reduction. ABB believes that IE5 SynRM technology – which exceeds by far the minimum efficiency performance standards (MEPSs) put in place by all major industrialized regions – provides the basis for sustainable efficiency of low-voltage motors into the future.

Efficiency is becoming a critical issue for manufacturers of motors and motor systems: the trend in the EU, United States and Asia is in the direction of further legislation – not only for motors but for the system in which they are embedded. This is why ABB is thinking ahead – with IE5 SynRM technology. 

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