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Hi guys!
I'm working on the trafos/drives/motors project and we are having a choice of 2 suppliers. We are pretty much decided on drives and motors but I have no experience with choosing <b>trafos 21kV/690V (~4000kVA) which have pretty much similar characteristics (losses, etc.) apart from harmonics</b>.
I've been searching around and I have found that norm <b>IEC 61000-2-4</b> (Compatibility levels in industrial plants for low-frequency conducted disturbances) tells a bit more about harmonics, nevertheless after several hours of googling can't find any norm's data to compare with data provided by trafo's suppliers.
Maybe some of you had an experience with choosing trafos and can tell me a bit more on the topic of harmonics:
<b>1. What are the limits of THD (Total Harmonics Distortion), THDi (current) and THDu (voltage) for trafos?</b>
<i>2. What are the differences between 3 classes enclosed in the norm IEC 61000-2-4? </i>
<b>3. Shall the special consideration be put on any type of harmonics: THDu or THDi? In other words, is any of these more harmful to the system? One supplier has very even levels of harmonics for both voltage and current, while the second one has low voltage harmonics (lower than other supplier) and elevated current ones (higher than other supplier).</b>
Regards,
Eric
I'm working on the trafos/drives/motors project and we are having a choice of 2 suppliers. We are pretty much decided on drives and motors but I have no experience with choosing <b>trafos 21kV/690V (~4000kVA) which have pretty much similar characteristics (losses, etc.) apart from harmonics</b>.
I've been searching around and I have found that norm <b>IEC 61000-2-4</b> (Compatibility levels in industrial plants for low-frequency conducted disturbances) tells a bit more about harmonics, nevertheless after several hours of googling can't find any norm's data to compare with data provided by trafo's suppliers.
Maybe some of you had an experience with choosing trafos and can tell me a bit more on the topic of harmonics:
<b>1. What are the limits of THD (Total Harmonics Distortion), THDi (current) and THDu (voltage) for trafos?</b>
<i>2. What are the differences between 3 classes enclosed in the norm IEC 61000-2-4? </i>
<b>3. Shall the special consideration be put on any type of harmonics: THDu or THDi? In other words, is any of these more harmful to the system? One supplier has very even levels of harmonics for both voltage and current, while the second one has low voltage harmonics (lower than other supplier) and elevated current ones (higher than other supplier).</b>
Regards,
Eric
