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Author Topic: Alright fellow campers...a frankenstein moment!!  (Read 6385 times)

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Offline RICH

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Re: Alright fellow campers...a frankenstein moment!!
« Reply #90 on: November 19, 2017, 11:12:08 PM »
Quote
ideal world we would not have any radiated RF interference

That's why you have  "Part 15 of the FCC Rules" plastered all over electrical items stuff.
does not apply to some countries though.  >:D  ;D

RICH
 
Re: Alright fellow campers...a frankenstein moment!!
« Reply #91 on: November 20, 2017, 12:48:24 AM »
Hi,
you're right in some countries they just don't care. In others they just print conformance notes and attach it to their equipment without being
anywhere near a testing lab.

There is to my knowledge  one accreditated testing facility in Christchurh and to have IEC schedule tests done can be tens of thousands of dollars.
Such testing and conformance costs are passed on to the buyer making well designed and made equipment expensive. A lot of the chinese compliance
marks are just plain fraudulent. Some of their gear is just plain electrically dangerous.

Then there is all the shortcuts we as consumers take. We all buy VFDs but has anyone bought the matching line reactors? I bet not, after all the device works
without spending all that extra.....so why bother.

Craig
My wife left with my best friend...
     and I miss him!

Offline rcaffin

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Re: Alright fellow campers...a frankenstein moment!!
« Reply #92 on: November 20, 2017, 01:55:43 AM »
For large (20 kW+) I can see line reactors being necessary, but are they really needed for little hobby-class VFDs? I ask because I do not know.

Cheers
Roger
Re: Alright fellow campers...a frankenstein moment!!
« Reply #93 on: November 20, 2017, 05:46:22 AM »
Hi Roger,
yes and no...Small VFDs have input filters in them already, usually just, and I mean JUST comply with reflected noise requirements and no more.
Large VFDs the user is expected to select the reactors/filters to suit. Thus if you have your own transformer then line reactors become redundant, you
use the leakage inductance of the transformer. If sharing a distribution transformer with other users will require reactors and if your neighbhour has
some sensitive equipment you will be required to install them.

The amount of noise a VFD produces is proportional to its output power. Ten 10kW VFDs produce as much hash as one 100kW unit. The smaller units
will have some filtration but some cheapskate will install the 100kW unit with nothing if he can get away with it. Does it really matter to you if the hash
interfering with your machine controls is your own 10 kW unit or the neighbhours 100kW unit?

I don't know whether you listen to AM radio much, I do when I drive and in certain rural areas the interference drowns out even the strongest stations.

Craig
My wife left with my best friend...
     and I miss him!

Offline rcaffin

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Re: Alright fellow campers...a frankenstein moment!!
« Reply #94 on: November 20, 2017, 06:06:53 AM »
OK, I understand both the theory and the economics. Fully.

Cheers
Roger