Lisrel: Line Start Synchronous Reluctance Motor with High Efficiency

The reluctance Technology allows an increase in energy efficiency of electric drives without a higher demand on resources due to oversizing or the use of permanent magnets.

Line-start motors can be operated at a synchronous revolution speed without complex control systems and also can be run up to speed without startup support. Since they work without slip when running in steady state no load-dependent losses are generated in the rotor. Using internal stream barriers line-start motors can be designed as reluctance motors without permanent magnets. These motors get up to speed quickly and reach the efficiency category IE3. Optimization of the rotor allows a specific configuration either for synchronous operation or good line-start behaviour. Prototypes demonstrate the benefit of this technology and show their advantages and limitations.

The rotors of the newly developed synchronous reluctance motors feature internal stream barriers. A combination in the generation of turning moments is achieved due to the additional squirrel cag. This becomes visible in the speed-torque characteristics. The aim is a characteristic curve, which shows a heavy starting torque and a steep gradient near the synchronous turning moment, to get as close as possible to synchronous operation and thus be able to “jump in”, which means to synchronize.

Measuring the degree of efficiency during the synchronous operation shows that the efficiency category IE3 for a nominal power of 180 W for the motor can be achieved despite of missing permanent magnets. Prototype P1 was designed for optimal torque during synchronous operation. Prototype 2 shows a profoundly good line-start capability. It can reliably accelerate and synchronize 25 times its own inertia when fed with a nominal voltage of 100 V at 50 Hz.