Re: Harmonics in electrical systems (back to basics)

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Hi there, not sure where to post if its wrong please move


I’m working a ship where we have a 6.6 kV 50Hz system that feeds 12-puls converter for propulsion, the same 6.6 kV is also transformed down to 400V for general use. This 400V is also used for feeding a 400V/400V transformer (500kVA) that is used to give power to refrigerator containers.  When we only running two diesel generators connected to 6.6 kV net, we get problem with the harmonics created by the converters on this 400V. From the measurement that I have done, we have a voltage THD on the 400 V about 7 to 8 % and it is mostly, due to the 12 – puls converter, the 11th and 13th harmonic that causes us problem.

Now, I’m not wondering about the theory behind as I’m a bit familiar with it but I’m wondering about the hardware. How big would it have to be as there is a space issue onboard and what would an estimated cost for such filter be? When searching for harmonic filters they usually is also used for power factor correction and therefore comes with larger capacitor banks. My only goal here is to remove the harmonics and from my own modest calculation by removing the 11th and 13th harmonic it would bring us down between 5% or 6 %.


Thx in advance for any ideas