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Harmonics calculation due to electronic motor drive

Harmonics calculation due to electronic motor drive

Harmonics calculation due to electronic motor drive

(OP)
Hi fellows
,
You helped me before, here I go again

Need to calculate/simulate how much voltage harmonics, a motor drive introduce in rest of supply system.

The motordrive is placed near the supplying generator.

Should I use the generator synchronous reactance or subtransient reactance as the supply networks impedance?

RE: Harmonics calculation due to electronic motor drive

Hej Petersen,

Subtransient reactance (x'') is the one to use. Remember that it is given at 50 (or 60) Hz. So you need to multiply with five, seven etc for the different harmonics.

RE: Harmonics calculation due to electronic motor drive

If this is running steady state, wouldn't you want to use xd?

Mike

RE: Harmonics calculation due to electronic motor drive

No. Because every current "bump" is over within less than a quarter period and contains frequencies up to 1000 Hz and more.

Steady state, yes. But not 50 or 60 Hz. You have to think about that to see what it means.

RE: Harmonics calculation due to electronic motor drive

(OP)
I think I got it:

If the current "bumps" are over within the time used for xd'' to change to xd' then I have to use xd'' ??

Will it be reasonable to use xd' or even xd as a worst case calculation?

RE: Harmonics calculation due to electronic motor drive

Wouldn't something close to xd'' apply any harmonics (other than the fundamental) for any duration for reasons similar to x2 being essentially xd''?  Isn't it the air gap flux that makes xd different from xd' different from xd''?  So even in steady state, a harmonic (just like neg. seq.) can exist without its impedance increasing away from the xd'' value.

RE: Harmonics calculation due to electronic motor drive

I thought that it depends on how x2 is defined...the Westinghouse T&D book has a long section regarding x2.  I don't have it at my fingertips just now....

Mike

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