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From the equivalent circuit of Induction motor, we see that Pmax or Tmax occurs when (Rexternal+r2)/slip= IZeqI. where Zeq is (r1+j(x1+x2)) . IMHO this is the basic equation. This also available in Wildi. From this equation the answer at slip 1 comes Rexternal+.333=IZeqI=...

Yes it will. Thanks Cos90 for sharing this, you seem to have good stuff. When I look back the reason of zero sequence - I was right and then solution is different from what I suggested. In my suggestion 30 degree phase angle  problem, will again appear which need to be resolved by ICTs (...

First thing is you are at right place to get all kinds of info. This forum will give you everything you need. I graduated in 1990 (Electrical) and writing PE in October 17. I also had similar feelings whether to write not to write, how come I can compete with young guys, what about references...

The discussion started with Cos90 brought  a scenario from t60 manual which states like this " In our example, the transformer has the Δ-Y connection. Traditionally, CTs on the Wye connected transformer winding (winding 2) are connected in a delta arrangement, which compensates for the phase...

When you have delta winding and a star connected neutral grounded winding on same side of transformer, you have two parallel paths for Zero sequence currents, one is to circulate with in delta and the other in the neutral. How much will go where will depend on the  resistances of the paths. I...

I hope the explanation makes sense. I have never dealt with grounding winding of a transformer because I have never worked in a ungrounded system, I mean it is really funny to have undergrounded system and then ground it by a separate wdg. However the concept is no rocket science, I must have...

I saw this. could not find anything like you mentioned. I think the theory of diff protection, I have covered the whole thing in my earlier post. We can achieve the same thing by many means. The manual t60 details how it is achieved in their relay. These new relays are very flexible in things...

Thanks a ton. The student in me remains agitated till I discuss this kind of  stuff with some one. When I saw the question, I knew what he wants to ask and did it right, but the student ?  You have been useful in fixing these loose ends, *** bits. 

Thanks. Is it legislated somewhere, except in practice tests solutions?

I never had an issue with turns ratio of a Xmer but while preparing for PE. I have been conventionally considering it same as voltage (Line/Phase) ratio whether in star star; delta delta or star delta  What should one answer for turns ratio when you face such a question in PE in star delta...

I had this question in my mind. In my working I have never seen this feature. I accept it as a theory only. And I do not know when technology provides you all time solution why you have to have a manual mode for bypassing purpose. ( I remember this inherent restrain feature in analogue English...

Lol

If you see para 430.6.A.1 Exception 3- It says whenever you have HP and current both from Name plate you take name plate current for everything. I read this when I did PPI -1 yesterday. Then I see PPI itself taking sometimes this sometimes that in different questions. Not allowing to settle at...

Second one- More I know NEC, more confused I am? The PPI-1 uses name plate rated FL current in some questions and Table derived FL in the other for similar situation. Anyone having any clear idea. 

Some of the questions in PPI practice test are really smart and good. Does anyone else has similar feeling?

If you have tailor made Xmers and CTs, percent Bias may not be of much use but, practical situations warrant this. Secondly this also eliminates mismatch due to unequal saturation conditions of CTs, difference in their ages may also cause this mismatch. ( Say I had to replace one of the CTs due...

You are right, this feature of second harmonic restrain can be achieved by many means, time delay (disabling while inrush) is one of them, the other is kick fuse ( i do not know how it functions, must be bypass as you mention), putting a filter for second harmonics and then using it for...

I appreciate you pointed this out. This was an example to take the reader to maths;  to make him understand the percent bias;  not the exact  values,  but yes percent bias is there in the settings of a differential protection. In case there is a mismatch of CTs it is used. I have  myself decided...