A wide range of technologies can be employed to provide customized, cost-efficient, and eco-friendly drive solutions. These include regenerative braking, automatic magnetization adjustment, copper rotors, 87 Hz operation, and intermediate circuit coupling. One company leading the way in this area is NORD, which develops, produces, and markets drive technologies and is an international supplier of all-in solutions. In addition to standard drives, NORD supplies application-specific concepts and solutions, addressing such special requirements as energy-saving drives and explosionproof systems.
Reusing Excess Energy
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 that 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
Intelligent control is another way to save. Operating with asynchronous motors, frequency inverters generally maintain the level of magnetization 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 magnetization when the motor is operated under partial load. Users can thus save up to 30% on 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 87 Hz in delta connection using a 400 V inverter, thus enabling the motor to run at a higher speed (up to 87 Hz) while maintaining the nominal torque. Raising the frequency to up to approximately 100 Hz will increase motor efficiency by up to 5%.
Materials Play a Role
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 optimized 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.
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