Technology news: May 2012
Line-start motors combine the best of synchronous and asynchronous
At the recent Hannover Fair, SEW-Eurodrive unveiled a range of line-start permanent magnet (LSPM) motors, said to combine the advantages of robust asynchronous motors with those of low-loss synchronous motors. The new machines, based on SEW’s modular DR motor, will be available in efficiency classes IE2, IE3 and IE4.
The three-phase asynchronous motors have squirrel-cage rotors containing additional permanent magnets. After an asynchronous start-up, the motor synchronises with the input frequency, and then runs in synchronous mode. There are no rotor or exciter losses, resulting in a high efficiency.
The four-pole motors (above) are available in four frame sizes from 71S to 100L. They are claimed to be two frames smaller than similarly rated conventional motors with the same efficiency.
The motors can operate directly from the mains, or with a frequency converter. Parallel operation of multiple motors in a group is possible.
The motors achieve their full energy-saving potential in continuous operations, such as driving pumps. They are ideal for applications with good speed stability – for example, as spin pump drives for supporting materials in textile machinery, or for airport luggage-handling systems.