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While migrating from ATV58 to ATV71 drives, how to confirm the existing line and motor chokes compatibility with ATV71?

Published date: 28 November 2018

The input line choke and output motor choke given in catalog are tested with the ATV71 drive and the performance is validated. If the impedance value of input and output filter changes, it may affect the performance slightly. It means, the harmonic % may be higher or lower depends upon input choke impedance % increase or decrease. The peak voltage at motor terminal may be higher or lower depending upon output impedance of the motor choke.

It is not mandatory to replace the line choke and output motor choke while migrating form ATV58 to ATV71. You can use the old choke, if the impedance % of old choke is above 3% or higher than the choke impedance%(calculate) given in ATV71 catalog. The impedance percentage can be calculated by below formula.

The impedance above 5% is not recommended, it may lead to higher output voltage drop and reduce the available torque on motor. The general thumb rule to size the inductance of the line choke is rated 3% to 5% impedance at fundamental frequency for the rating of the drive. The formula for calculation of impedance is below, I hope this formula can be applied for both input and output choke impedance calculation. 

L = ZV / (I * 2 ∏ f * √3) OR -----> Z(%) = ((L * I * 2 ∏ f * √3) / V)*100
Where ∏ = 3.141
L = inductance in Henries
Z = percent impedance desired (0.03 in this case)
V = supply voltage (line to line)
I = fundamental load current demanded from AC line/motor (Amperes)
f = fundamental supply frequency (Hz)

Sample calculation is shown below.

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