VFD line reactor and voltage drop

[Mike01]

Looking at a VFD project where the VFD and motors are purchased and installed by others and the drawings show a 5% line and load reactor for VFD's where the motors are being installed up to 350' away, as I continue reading there is also a voltage drop requirement requreing not more than 5% VD at the motor terminals, however at full oputput, my understanding is that the 5% line reactor will introudce 5% VD across it, with that the wire will have to be increased to meet the spcification requriements. with the input voltage hovering around 477V this would mean as soon as I leave the drive I will be around 453V, with the motor being rated at 460V [inverter duty] designed to operate at +/- 10% with the low side being approx. 414V if I can maintain not more than 3% VD from the VFD to the motor it would still be within the operating charasterstics of the motor with some flexibility for utility / system voltage sags that may occur, just wanted to see others experience with voltage drop and output reactors, on VFD's.

 

[mike_kilroy]

If you have an input 5% also, then you will drop 10% total thru the system if the 5% ratings are at your motor current rating.

Yes, you can drop so much to starve the motor and it will have to draw more current to make up for it. BUT since you have vfd you can just set it for slightly lower than base freq where the lower voltage intersects the v/hz curve for the motor and match it right up if that is an issue.

You would just make the base speed a tad lower and loose a tad HP. set max speed up to same as base speed as before to not loose speed. I would think you would be hard pressed to notice the slight HP loss from this slightly lower speed to base speed and above.

I think an input and output 5% reactor is too much - I would have left the 5% on output if it was felt the 350' leads needed it and just put a 1.5% on input.