Motor and drive act in concert

An integrated motor and drive package has been developed that looks set to succeed where previous designs have failed. Dean Palmer reports A cost effective, integrated motor and drive package has been developed that uses the latest inverter technology and a permanent magnet motor design to give OEMs a flexible, simple drive solution. The technology isn't groundbreaking, admittedly, but the design of the motor is innovative and the flexibility of the overall motor-drive package also deserves attention. The drive uses cleverly positioned heat sink fins that slot into the cooling fins of the motor, to assist in cooling the overall unit. The heat sink fins are placed into the moving air from the motor fan and airflow created by the fan is drawn over the heat sink. Because of this, the size of the drive heat sink is more compact than drives that use the natural convection concept and those used in other integrated motor and drive packages. In fact, it is not uncommon to see integrated motor-drive packages that employ a drive that is four times the size of the motor. The Concert-Drive has a length of 272mm, a width of 180mm, a height of 236mm and weighs approximately 13kg. As well as reduced overall size, OEM customers will also benefit from a reduced need for external cooling at low speeds, the easy mounting of cables, and the fact that custom modifications, such as special flange and shaft configurations, encoders, force vents or brakes, can easily be incorporated into the unit. Aimed primarily at pump, fan and specialist OEMs, the new 'Concert-Drive' is the result of a development partnership between AEG Lafert Motors and variable speed drives specialist Danfoss. Nigel Evenett, UK MD of AEG Lafert told Eureka: "The product is aimed squarely at major OEMs that want customised motor-drive packages. We only make motors so we are specialists in motor technology and manufacturing customer-specific motors. For the Concert-Drive, we've already got an enquiry for 800 units from one client." He went on to say that AEG expects to exceed 50,000 units sold in three years. The motor is a permanent magnet brushless AC motor. The arrangement of the motor windings was optimised using finite element analysis (FEA) and AEG claims the motor therefore has low losses from using better quality materials such as steel and copper. FEA was also used to emulate the dynamic losses and iron losses and the result is a motor that has a low cogging torque. The design uses high performance rare earth permanent magnets. But why will this design succeed where others have failed? Aside from its design and flexibility, Evenett offered other success factors: "We believe the market wasn't ready to accept these packages five years ago. Back then, mechanical engineers were buying motors integrated with black boxes of wizardry. Now, companies have much stronger combined skills and expertise in electronic and mechanical design." Competitors such as ABB, Siemens, Brook Crompton, Leroy Somer, VEM, Halter and SEW Eurodrive have all developed similar motor-drive systems in the past five years, most having met with limited success in the market. According to Evenett, "This is for various reasons but mainly because the solutions were not flexible enough. Some were over-engineered, some under-engineered, others had performance issues, the pricing was not customer focussed and the units were launched before the market was ready. "Concert-Drive is a tailor made solution for OEMs. With AEG, the customer benefits from our flexibility and cost efficiency which we get from manufacturing large volume AC induction motors and our permanent magnet know-how. With Danfoss, the client gets a global player that has expertise in variable speed drives." The unit currently comes in three frame sizes: IEC 71, 80 and 90. This offers a much more compact design than its AC induction motor counterpart which would normally be available in the IEC 100, two frame sizes larger. The company also claims that efficiency levels have been achieved that are higher than the CEMEP EFF1 levels for conventional induction motors. Both motor and drive are to IP55 and power ratings are from 0.55kW up to 2.2kW (a 4kW unit is already in development). There are permanent and induction magnet options (single and three phase), high efficiency and low noise designs, and it is even possible to order a 2.2kW unit in a size 80 frame. Speeds are possible up to 12,000rpm which is also good news for pump and fan manufacturers.