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`Super premium` IE4 contenders line up in Hannover

03 May, 2011

The world’s leading motor manufacturers are gearing up to offer machines that meet the IE4 “super premium” level of efficiency, even though the IEC has yet to define IE4 officially, and there are no plans yet to make IE4 mandatory.

At the recent Hannover Fair, several suppliers were showing IE4 contenders although, in one case, these were still at the prototype stage.

One of the front-runners in the IE4 race is the Brazilian motor-maker WEG which announced its contender, called WQuattro, last year. These motors, available in four- and six-pole versions spanning ratings from 0.37–7.5kW in frame sizes 80–132S, combine a conventional three-phase distributed winding with an aluminium-cage rotor containing powerful internal magnets. WEG says this combination makes the motors ideal for direct-on-line starting and for accelerating up to synchronous speed.

With this type of operation, the motor speed does not vary with the load – even if there are voltage drops or overload variations – as long as the mains frequency stays constant. There is no need for positioning or speed sensors, or special protection relays, and the low bearing temperatures that result from synchronous operation, lead to long operating lives with little maintenance.

The photograph above shows motors from WEG`s IE2 (left), IE3 (centre) and IE4 (right) families on the company`s Hannover stand.

Near WEG’s stand, SEW-Eurodrive was demonstrating its IE4 contender – a line-start permanent magnet motor which can either be connected directly to the power supply or operated with a frequency inverter. The DRU motors are based on AC asynchronous designs, using squirrel-cage rotors that contain permanent magnets. SEW says that the machines combine the benefits of rugged asynchronous motors and low-loss synchronous machines, with low slip losses.

SEW`s four-pole motors (above) cover the power range 0.18–2.2kW in frame sizes 71–100. They achieve their full energy-saving potential in continuous-duty applications such as driving pumps.

Another company exhibiting permanent magnet IE4 motors at Hannover was Marathon Electric, a division of the US-based Regal Beloit corporation. It claims that its SyMax IHP motor has losses that are 15% lower than similarly rated Nema Premium motors. The motor`s radial flux design is said to result in high levels of torque, efficiency and power density from a machine weighing less than a typical induction motor.

Marathon’s IP55-rated TEFC (totally enclosed fan-cooled) motors incorporate rare-earth magnets embedded in the rotor. The motors can be used as drop-in replacements for equivalent induction motors. They have a lower torque-to-inertia ratio than equivalent induction motors, resulting in a high dynamic response. The motors are available in IEC frame sizes 112-180 or Nema frames 182–286T and cover torque ratings from 13.5–400Nm.

One of the most interesting approaches to high-performance motors could be found on ABB’s Hannover stand. For its IE4 offering, ABB has turned to a synchronous reluctance technology that pairs a conventional stator with a loss-free rotor constructed using axially stacked iron laminations. It plans to sell the motors in packages with drives which, it claims, will achieve losses 40% lower than standard IE2 motors, resulting in payback periods as short as two years.

Like WEG, ABB says that its IE4 motors will have long, low-maintenance lives because of their low bearing temperatures. But, it adds that because the motors do not contain magnets, changing the bearings will be easy if they do eventually need replacing.

ABB had another trick up its sleeve. As well as the IE4 motor, it has produced a version of its synchronous reluctance machine which has been optimised for power density. This will allow users either to select a motor up to two frame sizes smaller than normal for a given output, or to boost outputs by up to 40% for a given frame size. This version will also be sold only with a drive.

A final contender in the Hannover IE4 stakes was Siemens, which was hedging its bets by showing “concept” versions of both permanent magnet and induction super premium efficiency motors. Details were sketchy, but the induction version, with a claimed efficiency of 94%, could be produced in versions up to 22kW and would be suitable for direct-on-line fixed speed, or variable speed, operation. No decision has been made yet whether to put either version into production.

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