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Magnet-free linear motor challenges mechanical drives

09 September, 2008

Siemens has developed a synchronous linear motor with a magnet-free secondary track. The company claims that the 1FN6 motor offers all the advantages of synchronous direct drives – such as high force densities and dynamic responses, minimal maintenance, low energy losses, and high precision – while being "very inexpensive", especially for long traversing distances.

Siemens linear motor

Siemens sees the motor (shown above) as a rival to mechanical drives such as gear racks and ballscrews, as well as an alternative to other types of motor, such as asynchronous linear and reluctance motors. It will also be ideal for applications where conventional tracks would need to be protected against the ingress of dirt.

Typical applications are expected to include handling and linked axes, as well as precise, dynamic feeding axes for water-jet and laser-beam cutting machines.

Until now, says Siemens, the high cost of the permanent magnets has limited the use of linear motors in many applications – especially in machine tools – where long distances need to be traversed quickly and precisely.

The fact that no permanent magnets are needed in the new motor’s track also means that it is easy to install and robust, according to Siemens. Large air gaps are possible.

The linear motors are expected be especially useful for applications such as water-jet or laser-beam cutting. The motor’s modular design allows it to be adapted to suit the application. Any number of secondary sections can be mounted next to each other to achieve long traversing distances. In addition, several primary sections can be operated on a secondary section track.

The first version of the 1FN6 linear motor is self-cooling and covers a force range from 880N to 7.92kN. The motors are designed to be used with Siemens’ Sinamics S120 drives. Prefabricated power and signal cables can be linked to connectors on the front of the drive, cutting installation times.

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