Boosting motor efficiency

Paul Boughton
Savings are a big issue in all industry branches, today more than ever, which leads many users to try and reduce the power consumption of drive systems.

However, such considerations should not merely focus on optimizing the consumption of individual electric motors, but should instead encompass drive systems solutions as a whole.

Providing user-specific, customised energy saving concepts, drive expert Nord ensures maximum cost efficiency and eco-friendliness. Nord employs a wide range of technologies to this end, including regenerative braking, automatic magnetisation adjustment, copper rotors, 87Hz operation, and intermediate circuit coupling.

When machine motions must be slowed down repeatedly or regularly, the released braking energy is not utilized in conventional frequency inverter applications. Instead, it is consumed by resistors and emitted as heat. Drives which reuse excess energy via intermediate circuits or regenerative braking provide a more efficient and eco-friendly solution. While a regenerative braking unit can feed other components elsewhere in a larger installation, energy generated and retained in a DC intermediate circuit can be consumed by the connected components directly without loss. In effect, less power is drawn from the mains.

Intelligent control is another way to save. Operating with asynchronous motors, frequency inverters generally maintain the level of magnetisation required for yielding the full torque over the whole speed range, thus causing unnecessary loss during partial load operation.

Nord SK 200E, SK 500E, and SK 700E series frequency inverters can save resources by automatically reducing magnetisation when the motor is operated under partial load.

Users can thus save up to 30 per cent energy. Furthermore, compared to grid-powered constant-speed units, inverter-operated asynchronous motors can be run at higher output frequencies in order to increase efficiency.

Motors with 230 V/400 V star-delta wiring, for example, can be operated at up to 87Hz in delta connection using a 400 V inverter, thus enabling the motor to run at a higher speed (up to 87Hz) while maintaining the nominal torque. Raising the frequency to up to approximately 100Hz will increase motor efficiency by up to 5 per cent.

To improve motor efficiency, Nord has also developed new concepts around materials, such as using copper rather than aluminum for the rotor squirrel cage. Copper with its smaller ohmic resistance allows for more economic drives of a given size. Alternatively, the motor power can be increased maintaining size and efficiency, making it easier to fit stronger motors into small installation spaces. An optimised synchronous motor with a high-quality permanent magnet on the rotor side can make for an even larger increase in performance, all along maintaining very high efficiency. Systems such as these and the specific control concepts they necessitate complement Nord’s portfolio of energy-efficient systems solutions.

For more information,

Recent Issues