Search results

Help Support Engineer Boards:

  1. A

    AutoCAD 2020 - MEP Tool Palette: Electrical Receptacles, Light Fixtures, Panels, etc.?

    Hi guys, I currently have a student educational version of AutoCAD 2020, which I'm trying to use to practice and improve my CAD skills. Unfortunately, my MEP tool palette is not as extensive as I remember in the AutoCAD MEP 2018 version (also a student educational version), which has now...
  2. A

    Silly question about standard dielectric absorption ratio

    Hey guys, I have a silly question about dielectric absorption ratio. Many times I have seen that the standard dielectric absorption ratio R 60 sec / R 30 sec judges insulation condition as follows: DAR < 1: Bad or dangerous insulation 1 =< DAR < 1.25: Questionable insulation 1.25...
  3. A

    Do synchronous generators have V curves like synchronous motors do?

    Hey guys, Does anyone know if synchronous generators have V curves like synchronous motors do? I came across V curves for synchronous motors while doing the Shorebrook PE Power practice exam, and the Wildi book also briefly touches on V curves for synchronous motors... but I don't remember it...
  4. A

    Synchronous machines ideal excitation: percent tolerance between Re(Ea) and |Vt|

    Hey guys, Quick question about ideal excitation of a synchronous machine. Normally a synchronous machine is ideally excited when Re(Ea) = |Vt| (the real component of the internal or induced voltage phasor equals the magnitude of the terminal voltage phasor). What percentage tolerance (e.g...
  5. A

    1-phase split-phase circuit: current flow not arbitrary?

    Hey guys, I was doing a few examples involving the 1-phase split phase circuit... this is the circuit type that is common in residential homes. Can someone confirm if the current directions I drew up for this 120/240 V circuit is correct? It seems that each current must flow in a specific...
  6. A

    DELETED

    (DELETED)
  7. A

    Fuses, circuit breakers, and protective relays: switching, sensing, and interrupting devices

    Hey guys, So I was in a practice session, and a topic came up about whether fuses, circuit breakers, and protective devices are switching, sensing, and interrupting devices. I want to confirm that my understanding of these OCPD devices are correct. Fuses are sensing and interrupting devices...
  8. A

    Cram for Exam Vol. 3 Question 26 - Grounding bank providing current to load?

    Hey guys, I have a question while re-practicing the Cram for Exam questions. How does a grounding bank provide current to a load? See the attached problem 26 from Cram for Exam Vol. 3. I see their explanation that the grounding bank doesn't provide any power to the 1-phase load, but it still...
  9. A

    Question about 3-phase autotransformer banks: what if they were connected line to line?

    Hey all, I have a quick silly question about 3-phase autotransformer banks. Many questions involving 3-phase autotransformers that I have seen typically have each 1-phase autotransformer connected between line and neutral. So the primary (V1 auto) and secondary (V2 auto) terminal voltages are...
  10. A

    How much time does it take for you to complete each practice exam?

    Hey guys, If you don't mind me asking, on average how long does it take you to complete each practice exam or exam session? After multiple repetitive and detailed practices of the practice exams I have, I started doing timed rounds this week. I started with the Complex Imaginary practice...
  11. A

    Conductor sizing for a single motor that is NOT stated to be continuous duty - 125% multiplier still necessary? PPI Exam 1 Question 35

    Hey guys, Quick question about conductor sizing for a single motor that is NOT stated to be continuous duty - is the 125% multiplier still necessary? PPI Exam 1 Question 35 has a single 3-phase motor that is NOT stated to be continuous duty. I still used the full-load current from the Motor...
  12. A

    MVA method and calculating 3-phase fault apparent power and 3-phase fault current when X/R ratio is involved: PPI Exam 2 Question 152

    Hey guys, PPI Exam 2 Question 152 is the only question I've seen so far in all the practice exams and questions I have that asks for solving the 3-phase fault apparent power and fault current with the X/R ratio involved. So I'm not quite understanding how/why the solution uses the X/R ratio the...
  13. A

    Underfrequency condition in electrical systems: PPI Exam 2 question 148

    Hey guys, Question 148 of PPI Exam 2 asks about an underfrequency condition in electrical systems. My question is: Doesn't underfrequency also cause overloads? From my understanding, due to generator droop, frequency is inversely related to real power. So the lower the frequency, the higher...
  14. A

    Capacitance to neutral? PPI Exam 1 Question 68

    Hey guys, PPI Exam 1 question 68 is about solving for a 1-phase, 2-wire distribution system's capacitive reactance per unit length. I tried to solve this using the NCEES-provided reference handbook. In the NCEES reference handbook, the formula for average capacitance to neutral is given as: C...
  15. A

    PPI Exam 1 question 38 - is the given solution correct?

    Hey guys, Can you please take a look at PPI exam 1 question 38 and its solution, and see if you agree with the solution? My initial attempt was that since the load power factor = 0.8 lagging given, the load angle theta = theta voltage - theta current = 36.87 degrees. Then on the transmission...
  16. A

    3-phase transformer Y connection: voltages remain constant during ground conditions? PPI Exam 1 Question 22

    Hey guys, I'm a little bit confused by something that PPI exam 1 question 22 solution states as true. PPI question 22 states to be true that in a 3-phase transformer, the Y connection ensures voltages remain constant during ground conditions. The solution then goes on to explain that an...
  17. A

    Ungrounded system with single phase to ground fault - line voltages? PPI Exam 1 Question 18

    Hey guys, I have a question about line-to-line voltages in an ungrounded Y system with a single phase to ground fault, from PPI Exam 1 question 18. The solution basically states that the line voltages will be sqrt(3) times higher than the phase voltages during a phase-to-ground fault. This...
  18. A

    Illuminance (lumens/area) of a hemispheric lamp: PPI Exam 1 Question 16

    Hey guys, PPI Exam 1 question 16 is about the illuminance of a hemispheric lamp. Now I know that illuminance E is basically lumens over area (E = lm / A), but... In the solution to this problem, when calculating area A = 0.5A sphere = 0.5 * 4 * pi * r^2, why is the distance d between lamp and...
  19. A

    Neutral-to-ground resistor purpose: PPI Exam 1 Question 14 vs. NCEES Exam Question 134

    Hey guys, I just want to clarify something about the purpose of a neutral-to-ground resistor based on the different ways it can be connected. PPI Exam 1 question 14 has a resistor connected between the neutral point of the 3-phase source and ground. The purpose of this resistor is to allow...
  20. A

    Power factor correction question - PPI Exam 1 Question 10

    Hey guys, PPI Exam 1 Question 10 is supposed to be a simple power-factor correction problem that asks for the capacitance needed to correct the p.f. The problem statement does not state whether the system is Y-connected or delta-connected. So when I first did this problem, I just thought Z = V...
Top