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Ernie... see Siraj’s definition in: http://control.com/thread/1026117631 "Vector Group Coding." Regards, Phil Corso

Schmooot... If you are referring to the 04-Jun-02 post, the answer is yes. Do you need details? Regards, Phil Corso

Mikebro... 3 RTDs will provide an average temperature if output is divided by 3 or if instrument is calibrated accordingly. Unfortunately, reliability is severely compromised. If one of the three fails open, there is no temperature measurement. Thus, the question to ask is how critical is...

Adil... Posts by Charles and Zouhen indicate there is still interest in your problem. How was it resolved? Regards, Phil

Ssatta (Prince)... further to my 14-Dec-11 post: 1) Using V, A, and PF parameters presented, total power drawn from supply is 43kW. 2) Ignoring PF presented, then total power drawn from supply is 61kW. Regards, Phil Corso (cepsicon[at]AOL[dot]com)

ssatta (Prince)... the current values clearly indicate an ampere unbalance. In fact the Ampere Unbalance Factor (AUF) per NEMA is 36%. Per IEC it is 44%! Your power calculation, however, is suspect. Using the maximum line-current and a guess-timate that PF is equal to 0.8, is incorrect...

'Electrical'... my first advice is for you to reveal the voltage level to which the cable is to be connected! If 11kV, then my next advice is for you to search Control.Com Archives for answers to similar questions! Regards, Phil Corso

Bruce… the method can be used where relatively small control-wire size results in an unacceptable voltage-drop. Of course, precaution regarding disconnection at the ammeter end, must be emphasized. Regards, Phil

Ebenezer... the answer is yes. In fact the stepup-step down principle can even be used to connect an instrument, like an Ammeter, a very long distance from the Current-Transformer (CT) to which it is connected. Regards, Phil Corso

Stephen... because Ibc and Ica are vectors, they too will have magnitudes and corresponding angles. Vector addition will yield angle 'c'. The trick is to know how to find the phase-angles associated with the phase-currents Ibc, and Ica. For an unbalanced system the delta-triangle will be...

Juan Carlos... using your values and ignoring any vector group having a 30 deg displacement, there is a circulating current in the secondary windings of 19.2 Amperes! Regards, Phil Corso

Juan Carlos... If transformer's Vector-Group is Yd or Dy, then circulating-current is dependent on Turns-Ratio. If Yy or Dd, then Voltage-Ratio is used! Regards, Phil Corso

Juan Carlos... ignoring losses and X/R values, I calculated 6+ amperes. For a more exact value the no-load secondary voltages and no-load losses must be known. It is unlikely these values will be found on the transformer nameplates, but they should be available from the FAT (Factory...

To Those Interested... you really should read my 1999 paper, presented to "The Journal of the System Safety Society!" One section entitled, "The Sacred Cows of Emergency Safety Shutdown" design, contains a discussion on "The Fallacy of TMR!" Regards, Phil Corso (cepsicon[at]AOL[dot]com)

Renato... excitation-voltage equals terminal-voltage minus the stator-winding impedance-drop. The formula is Ve = Vt - Is x Z ! However, excitation-voltage change is not directly proportional to terminal-voltage change, because an 'operating' motor is a constant kVA apparatus... thus an...

Steve, I apologize for not being clearer with my calc comment. I meant that I didn't use "Power" in the Unbalance-Delta equations to determine phase-currents and line-currents. Thus, the values I originally presented are still valid for the Calculation-Basis shown! An aside: the...

Steve, my calculation of power at 208V is incorrect. It is 75% of their 240V rating. But the calculations for amperes are not based on power. Instead, I used phase voltage, 208V, and element resistance. I believe you must agree that at rated design voltage of 240V, the resistance for a 7.5kW...

Tony... when connected to the 208V supply, line-currents Ia, Ib, and Ic will be 62A, 47A, and 62A, respectively. The values obtained are based on the following: o The resultant load is an Unbalanced-Delta. o At 208V, the 7.5kW heating-elements (call R1, R2, R3) will each require 6.5kW...

Ady... if component failure occurs on the same phase, then root-cause is usually related to a parameter (mechanical or electrical) significantly different than those found on the other two phase. I suggest you start by providing supply-side and drive-side voltage and current measurements...

Engineer... your comment seems a bit harsh. The use of three (3) Overload elements, instead of two (2), has greatly reduced the risk of single-phasing, open-winding, and phase-loss. There are quite a few Topics in the Control.Com Archives. If your search proves inadequate for your needs, let...