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Motors & Drives

Nau comments: “The efficiency performance of IE3 motors combined with variable-speed drives is better than that of IE2 motors with the same drive. The type and form of windings for IE2 and IE3 motors are the same; the difference is the amount of active material including steel lamination, copper and aluminium. What distinguishes IE3 motors from IE2 is the higher quality and quantity of the materials that compound the core of the motor.

IE4 induction motor line in the near future. This is possible for motors of 15kW upwards using low-loss materials by redesigning the core lamination.” Energy losses are mainly attributable to heat caused by

electrical resistance in the coil winding, losses in the rotor bars and slip rings, losses due to magnetising of the iron core, and losses from friction in the bearings. WEG claims it has found a way to limit motor temperature rise at low speeds by using its inverter-based Optimal Flux Technology.

Hybrid motors

WEG’s WQuattro super premium efficiency motors employ a hybrid design to exceed the requirements of the IE4 classification. These motors integrate a conventional three- phase distributed winding with a rotor featuring an aluminium cage and internal high-energy magnets. This combination makes WQuattro motors suitable for direct-on-line starting and acceleration up to synchronous speed. If required, WQuattro motors can be used with inverters to give an extended speed range with constant torque.

Fig. 2. WEG’s Optimal Flux Technology, which minimises motor losses as a whole, can significantly improve energy efficiency.

“IE4 motors available today have a new technology. They are Permanent Magnet Synchronous Motors (PMSM). The high- energy rare earth permanent magnets are quite expensive; that makes the motor more expensive, despite having less active material - in this case only copper and steel lamination - than IE3 motors. PMSM requires a drive to start and control the speed. They are not able to start directly from the grid. Another IE4 motor type is the line-start permanent magnet (PM) motor. In this case it is possible to start it directly from the grid but its size and weight is comparable to IE2. IE3 motors are normally heavier and physically bigger

than IE1 motors, but Nau says that IE4 permanent magnet motors (except line-start types) will be smaller and lighter than IE3 motors. He adds: “If we intend to reach the IE4 efficiency with induction motors, probably most of them will be little heavier than IE3. We are working towards having an

Fig. 3. ABB’s new motor and drive packages are claimed to have energy losses that are 40 per cent lower than for conventional motors, enabling them to meet IE4 requirements.

Customers upgrading motors on existing designs or equipment already in service benefit from the fact that WQuattro motors employ the same frame size as standard induction motors with the same output. WQuattro motors are available in four- and six-pole versions, with frame sizes from


Motor Driven Systems Conference The conference sessions will provide

Motor Driven Systems Conference is taking place on 9/10 November 2011 at the St Johns Hotel

in Solihull, UK, to provide a forum for discussing the latest developments and the impact of electric motor systems on energy and the environment. In addition, delegates will discuss

existing and proposed energy efficiency policies and programmes, as well as technical advances.

a platform for representatives from the UK government, organisations involved with motor driven systems, manufacturers and technical experts. Andrew Castle, a director of conference

organiser Touchwave Media, says: “By bringing together five trade associations with a common goal, MDS will deliver a truly unified message for the adoption of a ‘systems’ approach to motor-driven

apparatus.” Steve Brambley is the deputy director of

Gambica, the UK organisation representing the interests of companies in the instrumentation, control, automation and laboratory technology industries. He adds: “Delegates will leave with

an improved awareness of the benefits of system design and control, and the ability to apply this in the real world and see energy savings which equate to cost savings.” l 19

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