adccommunitymod (AutomationDirect) asked a question.
Created Date: June 26,2018
Created By: bradzik
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Line reactors for higher rated current have lower inductance. The manufacturer of VFD recommends a 4 %, 390 A line reactor at the input. I wonder if I can use bigger line reactors that I already have which are rated for 620 A and have inductance of 26uH. Their percentage impedance value is not given on the nameplate but I made below calculation: % Impedance = ( 2? x f x I x L ) / U * 100 % = 2.19 % f = 50 Hz, I = 620 A, L = 26uH = 0,026 mH = 0,000026 H, U = 400 / sqrt(3) (U is Line to Neutral Voltage in Europe) So apart from thet they are bigger (for higher current) they also have lower percent impedance. I am afraid that running at a lower current their effective percent impedance would be even smaller which also can be calculated from the above formula. Substituting for I the 390 A VFD rated current I get 1,37 % impedance. Is it bad? Would such line reactor offer less protection to the drive?
Created Date: June 26,2018
Created by: bradzik
Line reactors for higher rated current have lower inductance. The manufacturer of VFD recommends a 4 %, 390 A line reactor at the input. I wonder if I can use bigger line reactors that I already have which are rated for 620 A and have inductance of 26uH. Their percentage impedance value is not given on the nameplate but I made below calculation:
% Impedance = ( 2? x f x I x L ) / U * 100 % = 2.19 %
f = 50 Hz, I = 620 A, L = 26uH = 0,026 mH = 0,000026 H, U = 400 / sqrt(3) (U is Line to Neutral Voltage in Europe)
So apart from thet they are bigger (for higher current) they also have lower percent impedance. I am afraid that running at a lower current their effective percent impedance would be even smaller which also can be calculated from the above formula. Substituting for I the 390 A VFD rated current I get 1,37 % impedance.
Is it bad? Would such line reactor offer less protection to the drive?
Created Date: June 27,2018
Created by: Adisharr
I would contact the manufacturer of the drive in question. I know an oversized one can cause issues in smaller drives if your transformer is significantly higher capacity than what the drive would normally draw. Most of my experience is with much smaller drives though. I can certainly understand why you might want to use what you already have. I'm sure that size reactor is pretty pricey ;)