{"id":5122,"date":"2011-10-11T10:06:45","date_gmt":"2011-10-11T08:06:45","guid":{"rendered":"https:\/\/mag.ebmpapst.com\/de\/?p=5122"},"modified":"2024-03-12T17:58:10","modified_gmt":"2024-03-12T16:58:10","slug":"ec-technology-or-vfd","status":"publish","type":"post","link":"https:\/\/mag.ebmpapst.com\/en\/insights\/ec-technology-or-vfd_5122\/","title":{"rendered":"EC tech\u00adnology or VFD?"},"content":{"rendered":"

In an effort to reduce our Carbon emis\u00adsions many Govern\u00adments around the world encourage the use of vari\u00adable frequency drives (VFD) with induc\u00adtion motors. This deci\u00adsion is made on the under\u00adstanding that signif\u00adi\u00adcant energy savings are achieved through the fan and pump \u2018power law\u2019. The flaw in this deci\u00adsion is the over\u00adsight of alter\u00adna\u00adtive tech\u00adnolo\u00adgies such as EC motors and that there are hidden costs with vari\u00adable frequency drives.<\/p>\n

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Actual effi\u00adciency factor<\/p><\/div><\/div>\n

The power law theory states that the power consumed by the impeller is propor\u00adtional to the cube power of the change in speed; reducing the impeller speed by 50 per cent reduces the power input to 12.5 per cent. If the fan speed can be modu\u00adlated to meet a demand then signif\u00adi\u00adcant energy savings can be achieved. This law should be used with care as theory does not occur in prac\u00adtice. It assumes turbu\u00adlent air flow throughout the control range, and this is unlikely, and it does not consider fixed losses within the motor and drive. Signif\u00adi\u00adcant savings can still be achieved, but not quite as much as the law would indicate.There are some hidden costs with VFD\u2019s, for example they increase motor losses. IEC60034-31, selec\u00adtion of energy-effi\u00adcient motors including vari\u00adable speed appli\u00adca\u00adtions, advises that the addi\u00adtion of a VFD increase motor losses by 2 to 5 per cent; in adverse circum\u00adstances it can increase motor losses up to 15 to 20 per cent. The VFD also has its own losses with small drives being less effi\u00adcient than large drives. The losses are also depen\u00addant on the drive switching frequency. The loss is less with low frequency switching, but this produces mechan\u00adical noise from the motor. The drive is there\u00adfore normally set at a high switching frequency but this increases its losses, for example a 1.1 kW drive is typi\u00adcally 95 per cent effi\u00adcient at low and 92 per cent at high switching frequency. Another loss over\u00adlooked is that of power factor correc\u00adtion.<\/p>\n