Reducing DanFoss VSD switching frequency

Decibel noise, and EMI "noise" are inverse.

At lower switching frequency, you will have lower EMI but higher whine..

I keep 4khz as switching frequency, for my applications.

Good luck.

WOW!

we recently started using Danfoss drives in industrial application, running ASI controls in same vicinity.

The ASI system was affected intermittently by danfoss on 10HP motor (hard to find, but much trial and error)

I tried changing switching frequency, chokes, etc. etc etc.

not too much luck.

I ended up running affected asi circuit through shielded sealtite, Inside EMT tubing, and moved it 3 feet away from motor cable - finally, no noise from VFD

check with danfoss in Chicago (you found CR4, I know danfoss has a web site!)

we have been using altivars (telemecanique) for years, never saw this.

I would like to see others comments

I also use the SQD altivars in all the UPS locations I service on the east coast.

They work great, UPS specs have us run line and load in seprate conduits also any control wiring is also run seprate and at right angles with power wiring inside enclosure ie: stop-start-speed control-foward-reverse ect.

WOW??? You need to upgrade your installation techniques or else you will always have trouble with VSDs and the EMI and system reliability in general. You should be working on both ends. The VSD end with line reactors and the control panel end with transient surge protectors and isolation transformers on your power to the microprocessor based controls. That should be standard procedure if you haven't guessed it by now.

Hello,

Increasing switching frequency will end up will VFD output signal more close to AC, henece better performance of motor operation, but if you incrtease more you actually reducing the life time of your the inverter (you need to check the curve in the catalogue to see the limit).

If you reducing more (below 4KHz) you increase the noise generated by the motor, and if you increase more (below 2 KHz) the motor may not operate (specialy below 1.5 KHz).

Hope this will help you. if note please let me know

Safi

Way not using a sinus filter between the motor and the drive. A sinus filter is a combination of coils and capacitors, this unit absorbs the higher harmonics. So the output of the filter is a much smooter sinus.

Thanks for all ya comments. I would have to try out all the suggestions and recommendation before moving to the next drastic measure if necessary. The funny thing though is the cables to other similar instruments run in the same tray but yet I am not observing the same effect across the board. I am thinking it like due to the way the cable could have be twisted when tied in the run.

I have thought about fitting in the necessary cables but the cost involved and the disruption to production is going to be a major restricting factor. I think the only chance of getting that done is when everything else fail and production comes to a halt before that kind of decision would be endorsed. Whichever the case, I will test out the suggestions and see if situation improve. Thanks

Hi.

When you have the possibility to increasing the switching frequency it is to move the acoustic noise up in a range where it is not bothering the human ear.

Increasing the switching frequency does not change the motor performance!!!

The manufacturer of good frequency converters, VFD, have already tested their VFD's at the highest switching frequencies to be sure that the lifetime of the frequency converter is not reduced.

It seems that you have acoustic and EMC-noise. The acoustic noise can be removed by either increasing the switching frequency OR installing a LC-filter.

If you want to avoid this kind of EMC-problems, you have to be prepared to go all the way in changing the motor and control cables to the screened type.