SLC Synchronous Linear Motor

For sorting systems and long travel distances – substantial energy savings, high availability, no maintenance required

The basic requirements of single-item distribution systems are high availability, energy efficiency, and no maintenance.

Linear motors are an excellent alternative to conventional drives for these types of application. The synchronous linear motor SLC from SEW-EURODRIVE is not only suitable for long travel distances, but also reduces the energy consumption in S1 continuous duty drastically: often by more than 60%.

At the same time, especially manufacturers of sorting plants benefit from the new drive concept of SEW-EURODRIVE, which allows them to use a simple and modular plant design. The linear motor is the key to this flexible plant design: the limitations of rotating drives for the overall construction do not apply.

  Brochure: SLC Synchronous Linear Motor (PDF)

Areas of application
The motor opens up new developments in positioning applications. The motor is suited for applications where the propulsive force of inexpensive ferrite magnets is sufficient, where a great nominal air gap is required (e.g. 5 mm), and where travel distances are long.

The focus of development was first on sorters for transporting goods. They are used in various industry sectors: in distribution centers of postal and parcel services, in baggage handling systems for flight baggage, and in central distribution centers of mail order companies.

Previously common rotative drive principles of sorter systems
Some conventional drive systems are equipped with a chain that connects the carts with one another. The chain is driven by a gearmotor with chain sprocket and is pulled in circles. The chain sprocket does not have the form of an ideal circle but is a polygon. This is the reason why force peaks occur periodically caused by the so-called polygon effect of the chain sprocket. Persons working at the sorter are exposed to high noise levels caused by the chain.

In another drive principle, every cart is equipped with a blade that is pressed together by two friction wheels and is thrust forward. In particular with asymmetrical loads, these friction wheels are subject to high wear and slip during operation and when starting and stopping.

In these two operating principles, rotative movement is converted into linear movement. This means that mechanical wear is generated in the process and maintenance is required as a result. The principle of transmission reduces the overall availability of the system, limits the design options, and generates critical noise on the sorter.

Previously common linear drive principles of sorter systems

Asynchronous linear motors have been used for sorters for quite some time – also at SEW-EURODRIVE. They are free from contact, which means they are not subject to mechanical wear, and they are low noise.   The linear asynchronous motor is a double-chamber motor with aluminum blade. The load is balanced automatically by the smooth motor characteristic curve.

SEW-EURODRIVE has been producing the DLD series asynchronous linear motor as standard product for the sorter market for some time now. The advantages are cost savings in construction and design as well as in operation and maintenance.

New system solution with SLC synchronous linear motors

In sorters based on the new synchronous linear motors, the secondaries and the ferrite magnets are attached to the underside of the cart.

In the stationary primary of the linear motor, the frequency inverter generates a travelling electric field that moves the magnets and consequently the train of carts.

Energy efficiency is of major importance in sorter applications. Sorters usually operate at continuous duty in S1 duty cycle. A great advantage of sorters with SLC sychronous linear motors is therefore a high overall efficiency.

Typical system structure

Up to four primaries are connected in parallel to one inverter. The commutation information is obtained by encoder NL16, which is evaluated by the matching SEW frequency inverter MOVIDRIVE^®.

A special feature is that the drive system can cover up to two magnet gaps in the coupling area between the carts.