Harmonics mitigation
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MAKING MODERN LIVING POSSIBLE Harmonics mitigation Requirements and Danfoss Drives’ solutions

3 Harmonic distortion – an ever increasing problem The mains voltage supplied by electricity utilities to homes, businesses and industry should be a uniform sinusoidal voltage with a constant amplitude and frequency. This ideal situation is no longer found in any power grid. This is mainly because consumers take non-sinusoidal current from the grid or have a nonlinear characteristic, e.g. strip lights, light dampers, energy-saving bulbs and frequency converters. Because of the constantly increasing use of non-linear loads, deviations become increasingly serious. Irregular power supplies...

4 A Fourier analysis is a decomposition of the non-sinusoidal current wave-form into the sum of sinusoidal signals with various frequencies and amplitudes. Harmonic current distortion is caused by the rectifi er part of the variable speed drive, typically a 6-pulse diode rectifi er. The harmonic currents can be described as reactive current adding to the active current. The amount of harmonic current distortion is often described as a percentage of the fundamental current also known as total harmonic current distortion (THiD). Consequences Excessive distortion causes malfunctions. Most...

5 Prevent harmonic distortion of mains voltage and current Harmonic reduction techniques To avoid potential problems or to comply with standards such as product standard EN 61000-3-12,system standard EN 61000-2-4 or recommendations such as IEEE 519-1992 or G5/4 several diff erent harmonic reduction techniques for variable speed drives exist. The most common solutions are: ¡ AC-coils ¡ DC-coils ¡ Multi-pulse (12- and 18-pulse) ¡ Active fi ltering ¡ Passive fi ltering DC as standard The VLT® HVAC Drive, AQUA Drive and AutomationDrive series have built-in chokes. This dramatically reduces...

6 Prevent harmonic distortion of mains voltage and current Multi-pulse 12- and 18-pulse rectifi ers have for many years been considered the standard solution to reduce harmonic distortion from drives. In theory, the 5th and 7th harmonic currents (for 18-pulse also the 11th and 13th) are cancelled by phase shifting transformers and the use of two (or three) six-pulse diode rectifi ers. However, a signifi cant disadvantage of the multi-pulse harmonic reduction technique is the sensitivity to non-ideal supply voltage. Since some voltage imbalance or harmonic background distortion is always...

7 Harmonic Calculation Tool Simulate the harmonic disturbance with and without fi lter To avoid overloading and to secure mains voltage quality, a number of reduction, avoidance or compensation methods can be used with systems and devices producing harmonic currents. You can use the VLT® Harmonic Calculation Tool MCT 31 to include specifi c counter-measures in the planning stage and therefore ensure the quality of your system. The network feedback of electronic devices can be estimated to within 2.5 kHz, depending on the system confi guration and standard limits. The analysis includes...

8 Advanced Harmonic Filter Specifi cations Line voltage ±10% Frequency +/- 5% Overload current 160% for 60 s Effi ciency 0.98 True power factor 0.85 @ 50% load 0.99 @ 100% load 1.0 @ 150% load Ambient temperature 5¢ªC – 40¢ªC without derating The Danfoss AHF 005 and AHF 010 are advanced harmonic fi lters, not to be compared with traditional harmonic trap fi lters. The Danfoss harmonic fi lters have been specially designed to match the Danfoss frequency converters. By connecting the Danfoss harmonic fi lters AHF 005 or AHF 010 in front of a Danfoss frequency converter, the Features Benefi ts...

10 VLT® 12-pulse drives Reduced harmonics and increased network stability When reduced harmonics and increased network stability are desired for high power applications, the Danfoss VLT® 12-pulse drive off ers an excellent solution. Two standard 6-pulse rectifi ers are connected in parallel to a three-phase system, through a 30°-phase shifting transformer. By phase shifting the secondary windings, the sum of the secondary currents in the primary eliminates the 5th, 7th, 17th and 19th harmonics. This results in a THiD of approx.10 % compared with a THiD of 30% to 50% in a 6-pulse drive with...

11 Back-channel cooling Our unique design uses a ducted back channel to pass cooling air over the heat sinks with minimal air passing through the electronics area. This allows 85% of the heat losses to be exhausted directly outside of the enclosure, improving reliability 400 V AC Normal Overload High Overload Frame Amps kW Amps kW 600 315 480 250 F0 648 355 600 315 745 400 658 355 800 450 695 400 880 500 800 450 F5 990 560 880 500 1120 630 990 560 1260 710 1120 630 1460 800 120 710 F6 1720 1000 140 800 460 V Normal Overload High Overload Frame Amps HP Amps HP 540 450 443 350 F0 590 500 540...

12 VLT® Low Harmonic Drive VLT® AQUA Drive, VLT® AutomationDrive and VLT® HVAC Drive are available in low harmonic versions Where the performance of other low harmonic technologies depends on the stability of the grid and load or aff ect the controlled motor, the new Features Benefi ts Energy saving Lower operating costs Energy saving functions (e.g., sleep mode, standby mode). Variable switching frequency for lower switching losses High product effi ciency network changes Saves energy Reduced harmonics Improved power factor/reduced load on supply network Lower transformer, switchgear and...

13 PC software MCT 10 Ideal for commissioning, servicing, monitoring and performance logging. RoHS compliant VLT® Low Harmonic Drives are manufactured with respect for the environment and comply with the RoHS directive. Options ¡ dU/dt fi lters: Protect motor insulation ¡ Sine fi lters (LC fi lters): Reduce motor noise Back-channel cooling Our unique design uses a ducted back channel to pass cooling air over the heat sinks with minimal air passing through the electronics area. This allows 85% of the heat losses to be exhausted directly outside of the enclosure, improving reliability and...