Transformer for 18-pilses VFD 5

[slavag]

Dear All.
We need ordered transformer 36/0.4kV 1000kVA for feed few VFD's 18-pulses.
Are it some special transformer?
Thanks in advance

 

[Skogsgurra]

A 12-pulse is standard, but never seen an 18-pulse. Wouldnt 24 be more convenient if you want to reduce higher order harmonics?

Yes, I cannot imagine that an 18-pulse isn't special. Z windings ad such things..

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[LionelHutz]

Is this to be the 18-pulse transformer or is feeding a 400V system that has 18-pulse transformers connected to it?

 

[slavag]

This transformer will feed a 400V system, and VFD 18 pulse will be connected directly to bus, without an isolated transformer.

 

[LionelHutz]

The transformer can be a typical distribution transformer. The 18-pulse VFD transformers will reduce the current harmonics at each VFD to <5% THD. This will reduce the harmonic effects on your distribution transformer to levels that have little effect on them.

 

[slavag]

What will changed in scheme if used 6-pulse VFD instead 18-pulse?

 

[jraef]

Nothing with regard to the transformer you were referring to, unless your load on that transformer is close to the limit, in which case you may need to over size the transformer to handle the added heating caused by the harmonic current flow in it. You have not supplied anywhere near enough information to make a reasonable determination.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[slavag]

Sorry, this all information what I have on this moment.
sorry, I know that my Q-s is very..st.. , but you send to me enough information on the moment.

 

[VTer]

In the USA, transformers intended for heavy harmonic loading can be specified or purchased with "K-rating" The K-rating number of transformer is determined based on the summation of harmonic currents. The k factor is equal to the sum of the square of the harmonic frequency currents(expressed as a ratio of the total RMS current) multiplied by the square of the harmonic frequency numbers. Also take a look at ANSI/IEEE C57.110 for more details.

"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic — and this we know it is, for certain — then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". – Nikola Tesla

 

[electricuwe]

If you buy 18-pulse drives that already contain the phase-shifting transformers (usually as auto-transformers) to convert external standard three-phase supply to three Phase shifted systems, the benefit for the upstream components will be as follows:

- significant reduction of harmoncis, significant enough to get rid of special requirements for the MV/LV-transformer
- this will provide you the benefit of simpler strategy for spare transformers
- with such an Approach you will usually be able to meet the utilities requirements for harmonic currents