Motor Filter and Reflected Wave??

[sky2020]

Consider a cable with x m length, what is the equation or the value of the reflection wave based on the cable parameters? Do you have a reference to compute this? What can be the reason for a two pu transient voltage at a motor? Only wave reflection? I have no filter attached at the drive output. Is there a reference?

How would you design a good filter? What are the good filters in the market? Just an inductor? LC Filter? dv/dt filter? Wave trapper? a combination? How it can help reducing motor heating, motor noise, and motor vibration? Can you please direct me how the LC for a dv/dt is computed and sinewave LC are computed? For me, both are the same!

 

[xnuke]

Most engineers don't normally calculate any of this. Talk to the drive manufacturer. They'll be happy to help you with your application.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[FacEngrPE]

If you want to try to calculate a number, probably not worth your time, the critical item is the frequency component of the leading edge of the drives square wave output that causes the drive cable to resonate (1/4 wave). You need to know the speed of propagation of the particular cable you are are using - wavelength = propagation speed / frequency.

However there is usually a table in the drive instructions that indicates that filtering is required for cables longer than X. If you follow that rule, just like xnuke indicates, you should not have any trouble with cable length.

Reference:
Effects of AC Drives on Motor Insulation - Knocking Down the Standing Wave, ABB.

https://library.e.abb.com/public/fec1a7b62d273351c12571b60056a0fd/voltstress.pdf

 

[jraef]

What FacEngrPE said is based upon the fact that not all drives use the same firing scheme / algorithm. Some of the bigger players have developed specific proprietary firing schemes to reduce Reflected Wave propagation, so the distance charts from one mfr will not be the same, or applicable, to another. If your supplier does not have those charts available to you, they are not sophisticated enough to have done this.


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