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Paresh I have also been involved in similar projects in the Middle East and have some real horror stories as to what end users, consultants and drives companies DO NOT know and try to do thinking they know better (a real case of a little knowledge is dangerous !!). Price, not safety is usually...

OK. HVF as mentioned above is course "harmonic voltage factor" not harmonic distortion factor. Sorry about that - fingers move faster than brian at times ! Also, NEMA does restrict the use of NEMA rotor designs C and D (i.e. double cage/deep bar type rotors)to NON VFD fed and NON distorted...

OK. It's been while since I've been on this site. JBartos unwarranted comments last time kinda peed me off; at least I have contributed something meaningful and important. I have spoken at length with the Europeans and in the US regarding fixed speed explosion proof motors on distorted...

Check latter portion of recent thread "Using Explosion Proof Motor on Distorted Supplies" on this site re the issue of VFDs and long cable lengths. As you will read sinus output filter are better than simple output reactors depending on the type (and carrier frequency) of the inverter. The...

Suggest you measure the harmonic current distortion at the input the drives. If they have no AC line or DC bus reactors you will be looking at around 65-70% (maybe higher) total current distortion per drive at rated load (more if the load is less due to the discontinous current). If they...

Looking at the numbers it has to be remembered that the Ithd will increase with any form of mitigation at reduced load due to the more discontinuous nature of the input current. It is the magnitude of the harmonic currents which are important, not just the Ithd. On smaller drives without...

jbartos... OK. I note your comments. Lets leave it at that them. Over and out. ICEMAN

Jbartos I note your comments but have to wonder as to whether you have read and appreciated all that has been said. I agree that explosion proof ‘enclosures’ have been around a long time since emanating from the mining industries. However, we are not discussing the effect of harmonics on a...

Mmmm. If it's not Steve Barker then it must be Patrick Ramsden ! Ja oder nein ? Wie geht es Ihnen ? ICEMAN

Sed2developer.... You aint Steve Barker from Siemens UK are you now gone walkabout ? I heard you escaped from Stalag 17 (that's what an old Siemens Germany pal told me the Germans called the Siemens UK posting. You only got it if you done wrong !) The problem is that usually the...

sed2developer... Tut mir leid ! I was referring to the UK (and elsewhere) re "they were getting away with murder". The Germans were the ONLY one doing it right with regards to certification and technical aspects. That's why I ended up workly closely with Loher. Siemens did (in the late...

Alan Re EMC compliance for systems. It is a seperate issue but......What a mess ! People are getting away with murder. What is the point of EMC filters, CE marking et al only for the kit to be stuffed willy-nilly in an enclosure, crossed cabling ? The problem is that nothing is policed...

Sed2developer.... Guten tag. I would not go to Siemens UK (Stalag 17) - I have never found them that switched on. Go to Erlangen - no problem, real expertise there. UK - nein ! I know EExe motors as well having supplied a number of VFD/motor packages. A lot more problematic that any other...

Hi Alan With regard to your questions…. Re approved thermistor relays. Having equipment manufactured to European Standards has little directly to do with safety in hazardous areas. Afterall you can buy an EExd motor built to these standards (they all are in the EU), connect a VFD to it and...

jbartos... 1. Re VFDs housed in the hazardous area.....That is why it is unusual. It's usually a cost issue but on some applications it is a requirement. The smaller the VFDs the easier it is. On some sites (Middle East) the kit is miles away from the main switchboard so locating smaller...

Alan I take it you are based in the UK (hence BS EN standards reference). My direct involvement in these matters ceased almost 10 years ago so I may be out of date in some areas. Although nothing much, as far as I am aware, has changed during this time. Despite what the standards say I...

jabartos....you have lost the thread here ! The motor is in the hazardous area and the VFD in the safe area ! It is the effect of the sythesised voltage and current waveforms, which contain harmonics, on the explosion motor is the problem (i.e. the interaction of the VFD output waveform and...

Hi aolalde - it's lunchtime so it's OK for me to reply to you re ex motors and VFDs. The US is a long way behind Europe in the safe application of ex motors and VFDs. It was in the early 1980's that Germany companies suh as Loher and F & G pioneered the ex motor/drive package concept with PTB...

jbartos.... My words regarding flameproof motor shaft seal problems due to harmonic problems come from Ron Sinclair, Principal Certifying Officer, BASEEFA (British Approvals Service for Electrical Equipment in Flammable Atmospheres). They are dated Feb 1988 and were made during a conference we...

Your clients's motor is 1500HP based on rated speed of 1000 rpm. So from 0 rpm to 1000 rpm the power (HP) is directly proportional the speed; the speed is (almost) directly proportional to the applied armature voltage if we ignore the effects of armature reaction et al. If the gearing is such...