Yes, Bill. I think your memory fails. You need to review Steinmetz' texts about symmetrical components to get the definition of negative sequence right. It is NOT about phase sequence.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's...
From https://electrical-engineering-portal.com/erection-procedures-of-earthing-arrangements-tnc-tn-s-tnc-s-and-tt
N says how the (transformer) neutral/Midpoint is grounded and there T means Ground (Terre) while N means Neutral (Neutre) and T means dug into the Earth we live on (Terre, again)...
And thanks to you! A happy ending, it seems. And your flamboyant writing makes it all the better.
But, as you know. After every sh*t work - there's also some paper work to do. Use soft tissue. It wipes best...
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half...
OK, understand now.
Simple answer: Yes.
A more realistic answer: It depends.
If windings are designed for that voltage. If bearing life will be OK at that speed. If the motor/coupling are well balanced and vibration levels do not get too high. And many such things. Yes. It is being done...
I wouldn't say unanticipated. When your V/Hz ratio can´t go any further, then you are in field weakening. That is known and hardly unanticipated. The torque goes down and you are running constant available power instead of constant available torque.
If you wire a Y motor in D, then you can...
Yes. And you can have full torque at zero as well. A ride in a modern elevator shows that. Empty car or full, it accelerates from zero to full speed up/down, decelerates to zero and stops there when door opens. OK, mechanical brakes applied at zero speed. But that is not the case in container...
This is definitely far from my daily work. But I have got similar questions from factory owners that didn't see the distinction between the risks involved in switching MV at elevated power levels, which this is for me, and the finer points in LV drives.
I have declined any involvement in such...
Sorry, got a long phone call before I hit "Submit" button. RR seems to have answered your questions in the meantime. Delhi shouldn't be too hot - or is it? Never been there.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it...
A few simple questions:
1. Is the motor overloaded? I may be tempting to "adjust" the overload protection and then find out that motor windings get hot. If that is the case, I'm not so sure that more cooling helps in the long run. There are always hot spots where the increased cooling doesn't...
I wouldn't say that it is as bad as Jeff says. That example was from an extremely demanding application. For most loads, you can use the 10 Hz limit without any problems. For fans and some pumps - you can go slower.
The FAG factory in Schweinfurth, Germany (now re-named) had similar problems...
A few curves from the British association of drive and motor manufacturers. Al major makes are represented. And a few less known.
The peak voltage increases with cable length, as Bill said. But when cables get longer than around 100 m, the dispersion reduces that influence.
But it is...
I would say that 10% is OK. You still get full torque. But the slip shows.
BTW, there are sensorless (no encoder needed) VFD:s that go much lower. I have been promoting them for decades. But no one seems to believe it is possible. It is.
Gunnar Englund
www.gke.org...
A quick web search brought this up:
https://www.eng-tips.com/viewthread.cfm?qid=444795
Jeff shows the curves
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
Yes, the torque curve moves horizontally along the frequency (or RPM) axis. At least at the first approximation. So, having slip frequency 1.33 Hz produces the same torque at 10 Hz as it will at 40 Hz.
But there are things like windage and other losses that eat some of the torque at 40 Hz. So...
That could happen here, too. MBA:s are resourceful and inventive...
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
Got it. But I think that they can get that idea without misreading EngTips.
I had to wait several days for the wood chips to get cleaned from the pipeline with a "bold" bend in a pulp/paper mill only half a year ago. Cold, dark, no schedule. What the management said should take a few hours...
Jeff said: 24 May 19 19:44
"Guys (or Gals as the case may be)...
THERE IS NO VFD. That was someone's misinterpretation of the word "drive" which was meant to refer to the MOTOR. The OP stated that there is no VFD so lets not keep going down that rabbit hole..."
I (me, myself and Skogs) used...
SparWeb, I don't think your capacitor was "broke". It was just plain too small with the 10 uF and 1 k load. Not to mention the 1 uF you started with.
Put it back in your junk box. You may need it some other time.
Gunnar Englund
www.gke.org
--------------------------------------
Half full -...
Sorry, Rout is 5 kohms. Still not serious.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
Right, Keith!
I ran a few LT Spice simulations and they show lots of problems with SW setup. Not to talk about those wave-forms shown. If the sine looks like a string of half arcs - there is a serious problem. That problem is more in the brain of the person that drew the wave-forms than IRL...
