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How has the new IE4 classification changed the motor market?

08 August 2013

The IE2 regulations effectively cleaned-up the lower efficiency end of the market; if an application requires a motor to operate only occasionally, then its energy consumption is not so critical.

A cutaway of a Bauer PMSM IE4 unit showing its internal construction

Users just want the cheapest machine they can buy that will be reliable in an application in which the motor is rarely used; the IE2 regulations are intended to make sure that new motors being supplied for these types of application meet a minimum standard of efficiency. But what about motors that run virtually continuously near their full capacity?

The IE4 (Super Premium Efficiency) classification is something many manufacturers are talking about and fewer are actually delivering. There is a cost premium, of course, yet the current market uptake is driven more by economics than legislation. For a small to medium sized electric motor that is running close to capacity for the majority of the time – one used in a continuous manufacturing process for example - then the additional investment in terms of purchase cost is outweighed by the ongoing energy savings in a relatively short time.

Motors that meet IE4 energy efficiency standards are usually permanent magnet types, where the permanent magnets are generally made from rare earth metals. They are more expensive to manufacture but offer significantly higher efficiencies of the order of 96 percent.

In order to illustrate these higher efficiencies, an end user in Germany carried out a direct product comparison test to see how an IE4, super premium efficiency permanent magnetic synchronous motor (PMSM) performed against a standard asynchronous motor.

The test was carried out on a Hüber disc thickener at a wastewater treatment plant in Germany in partnership with inverter drive specialist Danfoss (see DPA January 2013 page 32). Once installed the PMSM motor (supplied by Bauer) was found to operate with 87.7 percent efficiency and delivered energy savings of almost 40 percent compared with the equivalent asynchronous motor performance. Markus Kutny, a product specialist with Bauer Gear Motors, takes up the story:

“In today’s market energy efficiency has to be one of the key determining factors when specifying geared motors. Energy prices are only going to go one way so it is important that a drive’s lifelong running costs are considered, rather than simply the cost of procurement. We have developed the new motor range in anticipation of the new IE4 classification and to offer our customers the very best in terms of efficiency.”

Bauer Gear Motor’s range of PMSMs already fulfils the requirements of the soon-to-be-implemented IE4 classification. The PMSM series is an environmentally friendly range of motors, employing a highly efficient rotor design that integrates embedded rare earth permanent magnets in place of the squirrel-cage rotor configuration of conventional induction motors.

The PMSM design offers a number of key benefits: there are no heat losses associated with the rotor, total losses from the motor are down by approximately 25 percent, and motor efficiency is up by at least 10 percent. For the PMSM user, this improved performance translates into lower total cost of ownership (particularly as a result of the motor’s reduced energy consumption over its lifetime), and a reduction in CO2 emissions.

PMSMs offer efficiency gains even under partial load conditions; under rated operating conditions the efficiency gains are significant. They also have considerably higher power density (therefore a smaller installed volume for a given load) and reduced weight. Indeed, PMSM drives can produce more torque per installed volume than conventional induction motors, so it is often possible to specify a smaller motor to save space and unnecessary expenditure.

A common criticism of permanent magnet motors concerns the sharp drop in efficiency that can be experienced when they are run outside their ideal operating speeds and loads. Bauer has taken steps to mitigate this problem and claims its PMSM motors maintain high efficiency levels within a wide partial load range, up to a load factor of 1:5.

The synchronous design of the PMSM motors means that not only are they superior at converting electrical into mechanical energy, but they also offer the added benefit of delivering a constant speed (so long as the mains frequency does not vary), independent of load or mains voltage variations. They provide an energy saving drive for fans, pumps and compressors, as well as constant torque applications such as lifts and conveyors.

Bauer’s PMSM motor series is available in ventilated and non-ventilated configurations across the power range from 0.55kW to 15kW. They operate on 380V to 500V power supplies, and are rated for inverter duty, offering an extended speed range with constant torque.

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