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Zach Stone, P.E.

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Zach Stone, P.E. last won the day on October 12 2019

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About Zach Stone, P.E.

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    Lead Instructor for Electrical PE Review (.com)

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  • Engineering Field
    Electrical Power, Industrial Controls, Field Troubleshooting, Construction Management, Turbo Generators and Power Generation, 24hr Production Facilities
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    PE
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    TI
  • Discipline
    Electrical

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    http://www.electricalpereview.com

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  • Gender
    Male
  • Location
    USA
  • Interests
    Teaching Electrical Engineering

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  1. Magnetic circuits used to be one of my least favorite types of problems on the electrical power PE exam.It seemed overly complicated and resources that taught this type of problem were hard to find without diving too far into the subject of physics, which is beyond what the PE exam tests on. The two videos below go over how to: Relate the magnetic circuit variables (f = ΦR) to electrical circuit variables that we are more familiar with (V = IR). Convert any magnetic circuit, even with an air gap, into an electrical equivalent circuit. How to write Kirchoff's Current Law (KCL) equations using magnetic circuit variables (f = ΦR). How to combine series and parallel reluctances (R) in a magnetic circuit to determine the total equivalent reluctance (Req) To make sure you really understand transformer flux and magnetic circuit problems, we also included two practice problems worked out and solved on video for extra practice. 1. Transformer Magnetic Circuit, Flux, and Reluctance Practice Problem 2. Dealing with Series and Parallel Reluctance in Magnetic Circuits
  2. @Eng-Moe (if you @ people they are more likely to see it).
  3. The original post in this thread (instead of making a new thread and cluttering the board) has updated for 2020 and 2021 to include our new recommended references based on our experience helping engineers pass. I hope this helps you purchase the right books to help you with the electrical power PE exam.
  4. Nice user name! Subscribe to our Electrical and Computer FE Exam YouTube Channel. There are only a few videos but we will be adding to it every week. If there is anything particular you are looking for help with let me know and I'll see if we can can add some videos on the subject.
  5. Looking for specific help on Linear Systems for the FE exam? Direct message me.
  6. Switched RL circuits can be pretty difficult. In this video, we cover how to quickly solve for iL(t), the transient (natural) response of switched RL circuits by analyzing the circuit before and after the switch is opened. Video Table of Contents: 0:16 - Problem Statement 1:10 - Transient Response Definition 2:15 - The circuit at time less than 0 (switch closed) 3:17 - Solving for the inductor current iL(t), and the two-loop currents (i1, and i2) using KCL - Kirchoff's Current Law 6:29 - The circuit at time = 0 (when the switch opens) 6:42 - Inductor and Capactiro behavior when time is infinity (∞) and the system is stable 7:45 - Simplified circuit when time is equal to infinity (∞) 8:59 - IiL(0-) and iL(0+) 10:04 - Solving for k1, the constant of the Transient Response 10:57 - Solving for 𝞃, the time constant of the Transient Response (Tau) 12:47 - Solving for the equivalent resistance using the Thevenin equivalent circuit 14:55 - Solving for the transient response iLN(t) Answers: Current in loop 1: i1 = 1/2 mA Current in loop 2: i2 = 1 mA Current through the inductor: iL = 1/2 mA Current through the inductor at time equals infinity: iL(t = ∞) = -1/2 mA Current through the inductor right before the switch is opened: iL(0-) = 1/2 mA Current through the inductor right after the switch is opened: iL(0+) = 1/2 mA Current through the inductor right when the switch is opened: iL(0) = 1/2 mA Thevenin equivalent resistance seen by the inductor: RTH = 2/3 Ω Transient Response Constant: k1 = 1 Transient Response Time Constant 𝞃 = 15/2,000 seconds = 7.5 mS The Transient (or Natural) Response of the RL Circuit: iLN(t) = e^(-2000t/15) mA Can you solve it?
  7. Need help with a specific part of electronics that you'd like to see a video on? Reply to this thread or send me a private message.
  8. In this video, we'll teach you how to solve Electrical and Computer FE problems on diodes and Zener diodes and how to tell if they are operating in forward or reverse bias. Video Table of Contents (Click to Jump): 0:00 - Introduction 0:46 - Biasing 1:30 - Idea Diodes 3:09 - Idea Diode Example Problem 11:05 - Zener Diodes 12:01 - Zener Diode Example Problem
  9. Most engineers already know that power factor (PF) is the cosine of the power angle (θ). But did you know that the power angle (θ) actually comes from the phase angle of the total connected impedance (Z)? This is a small detail that most engineers miss while studying for the PE exam that can result in incorrect answers and a lower overall exam score, making it harder to reach the passing "cut score" of the PE exam. To help you understand why the power angle (θ) is actually the circuit impedance angle (θz), I'll teach you all the tricks and shortcuts you'll need to quickly calculate the power factor (PF) of a circuit. I'll also explain all of the subtle details that power factor can tell us about a circuit such as the relationships between: Voltage (V) and current (I) Reactance (X) and resistance (R) Real power (P) and apparent power |S| Complex power (S) and reactive power (Q) I'll also talk to you about the special conditions that exist during unity power factor such as: Why the power triangle no longer looks like a triangle Why the apparent power |S| and real power (P) are identical even though the units are different (VA and W) Why the reactive power (Q) will equal zero VAR Why the reactance (X) will equal zero ohms If you'd like to print the contents of the video, including all of the diagrams, graphs, and formulas, head over to the full length article: Electrical PE Review - Power Factor Basics for the PE Exam, Phasor Diagrams and Power Triangles Explained I promise that even if you're well familiar with power factor (PF), you'll still learn a new new trick or two.
  10. Our entire chapter on power electronics (Power Supplies and Converters) is included in the free trial of our online study program for the electrical power PE exam. It includes all reference text, practice problems and all example videos. Feel free to sign up and use the material for as long as you like. Don't forget to print it out to take it with you to the exam (while you still can before it transitions to CBT). Electrical PE Review - Chapter 5.2 (NCEES® II.B.2.) Power Supplies and Converters: Introduction and What to Expect Video Example - RMS Voltage, Average Value, Peak Voltage, and Peak to Peak Voltage Video Example - Period, Cycles, and Frequency Video Example - Leading vs Lagging and Phase Shifts Video Example - Phase Shifts Converting between degrees and radians Calculating the phase shift in seconds Video Example - Instantaneous Power, the Product of Instantaneous Voltage and Instantaneous Current Video Example - Instantaneous Power Calculating Real Power (P) and Reactive Power (Q) Video Example - Graphing Sine functions Video Example - The Ideal Diode Thyristor and Silicon Controlled Rectifiers (SCR's) Video Example - Positive Half Wave Diode Rectifier Video Example - Negative Half Wave Diode Rectifier Video Example - Full Wave Diode Bridge Rectifier Video Example - Full Wave Diode Bridge Rectifier with A Smoothing Capacitor Ripple Factor, r Ripple Voltage and Sawtooth Wave Forms DC Voltage (VDC), or Vavg Video Example - Ripple for Sawtooth Wave Forms Video Example - Three Phase Half Wave Diode Rectifier Key Formulas Electrical PE Review - Free Trial Sign Up
  11. I've been getting a lot of questions lately from students in our online program about the Two Wattmeter Method. Typically, these problems are very easy to solve if the system is balanced. However, if the system is unbalanced it can be quite difficult to derive the correct formula depending on how both wattmeters are connected. I figured if our students have been scratching their heads on this one, then a lot others probably have been too. Here are three new YouTube videos published today taken directly from the recording of last semester's live class. I hope this helps and please feel free to ask any questions in the thread. The full article where this information comes from can be found here: https://www.electricalpereview.com/3-steps-for-solving-the-two-method-wattmeter-problem/ ______ 3 Steps for Solving the Two Method Wattmeter Problem: Contents: Basic Rules, Circuit and Formula P = W1 + W2 (Two Method Wattmeter) Phasor Diagrams and Solving for W1 and W2 (Two Method Wattmeter) Shortcuts and Tricks (Two Method Wattmeter) 1. Basic Rules, Circuit and Formula P = W1 + W2 (Two Method Wattmeter) In Part 1 of the Two Method Wattmeter series, we are going to show you: 1. The three "rules" for using two wattmeters to measure the total power of a three-phase balanced or unbalanced circuit *For example: if the negative (-) voltage reference for wattmeter 1 (W1) is on C phase, then the negative (-) voltage reference for wattmeter 2 (W2) MUST also be on C phase. Rule #1 - The negative (-) voltage reference for both wattmeters MUST be on the same phase (both on A, B, or C). Rule #2 - The line current measured on each phase MUST be the same phase as the positive (+) voltage reference for each wattmeter! *For example, if the positive (+) voltage reference for wattmeter 1 (W1) is on A phase, then wattmeter 1 (W1) MUST ALSO measure the line current on A phase. Rule #3 - The positive (+) voltage reference for both wattmeters MUST NOT be on the same phase! *For example: if the positive (+) voltage reference for wattmeter 1 (W1) is on A phase, then the positive (+) voltage reference for wattmeter 2 (W2) MUST NOT be on A phase. 2. How to derive the two method wattmeter formula commonly seen in books depending on which phases the positive (+) and negative (-) voltage polarity for wattmeter 1 (W1) and wattmeter 2 (W2) are connected to: P3ø = W1 + W2 In the configuration that wattmeter 1 (W1) and wattmeter 2 (W2) are shown connected in this video, we can expand this formula into: P3ø = |VAC|·|Ia|·cos(θ-30º) + |VBC|·|Ib|·cos(θ+30º) 2. Phasor Diagrams and Solving for W1 and W2 (Two Method Wattmeter) In Part 2 of the Two Method Wattmeter series, we are going to show you: 1. How to draw the phasor diagram for both wattmeter 1 (W1) and wattmeter 2 (W2) depending on how each wattmeter is connected according to the three "RULES" from Part 1. The phasor diagrams will depend on which phases the positive (+) and negative (-) voltage polarity are connected to for wattmeter 1 (W1) and wattmeter 2 (W2). 2. How to easily derive the correct power angle (θ) for both wattmeter 1 (W1) and wattmeter 2 (W2) graphically using both of the phasor diagrams we set up. *Here's the trick! One of the line voltages being measured by either wattmeter 1 (W1) or wattmeter 2 (W2) depending on how they are connected will be NEGATIVE (CBA) SEQUENCE, and one will be positive (ABC) sequence. *Inside the cosine function in the power formula, one of the wattmeters will have θ MINUS thirty degrees while the other will have θ PLUS thirty degrees depending on how both wattmeters are connected: cos(θ-30º) cos(θ+30º) 3. Shortcuts and Tricks (Two Method Wattmeter) In Part 3 of the Two Method Wattmeter series, we are going to show you: 1. How to quickly identify which of the two wattmeters (W1 or W2) has the θ MINUS thirty degrees inside the cosine function, and which has the θ PLUS thirty degrees inside the cosine function WITHOUT taking the time to draw out the phasor diagrams. *It's extremely important to know how to draw both of the phasor diagrams (Part 2 in the Two Method Wattmeter Series) and how to derive the power formula commonly see in books (Part 1 in the Two Method Wattmeter Series) because in doing so you'll be able to answer just about any and every two method wattmeter question on the Electrical Power PE Exam. *HOWEVER! Time is really important during the exam because you only have a certain amount of time to answer each question. *Because of this, sometimes it is helpful to know how to QUICKLY identify which wattmeter the cos(θ-30º) and cos(θ+30º) terms belong to. 2. If the system is positive sequence (ABC), look for the negative sequence voltage. In a positive sequence (ABC) system: The A line voltage is measured from A to B (VAB) The B line voltage is measured from B to C (VBC) The C line voltage is measured from C to A (VCA) In the example circuit used in the video, wattmeter 1 (W1) is connected across A (+) to C (-). The line voltage that wattmeter 1 (W1) is measuring is the negative sequence C line voltage (VAC), NOT the positive sequence C line voltage (VCA). This means that the formula for the power measured by wattmeter 1 (W1) will have the 30º minus theta term inside the cosine function: In comparison, in the example circuit used in the video, wattmeter 2 (W2) is connected across B (+) to C (-). The line voltage that wattmeter 2 (W2) is measuring is the positive sequence B line voltage (VBC). This means that the formula for the power measured by wattmeter 2 (W2) will have the 30º plus theta term inside the cosine function: The wattmeter (W1 or W2) that has the 30º minus theta term inside the cosine function and the wattmeter (W1 or W2) that has the 30º plus theta term inside the cosine function always depends on how the wattmeters are connected. There will always be one wattmeter measuring a negative sequence line voltage, and a wattmeter that measuring a positive sequence line voltage. If the system is balanced, it does not matter which wattmeter formula has the 30º minus theta term inside the cosine function, and which wattmeter formula has the 30º plus theta term inside the cosine function since the line voltages magnitude and line current magnitudes will be equal. For example, if our example circuit used in the video is balanced then: |VCA| = |VBC| = |VL| and |Ia| = |Ib| = |IL| We can use this to simplify the two method wattmeter formula for a balanced system only: P3ø = |VCA||Ia|cos(θ-30º) + |VBC||Ib|cos(θ+30º) P3ø = |VL||IL|cos(θ-30º) + |VL||IL| cos(θ+30º) P3ø = |VL||IL|[cos(θ-30º) + cos(θ+30º)] __________________________ The full article where this information comes from can be found here: https://www.electricalpereview.com/3-steps-for-solving-the-two-method-wattmeter-problem/
  12. I've been getting a lot of questions lately from students in our online program about the Two Wattmeter Method. Typically, these problems are very easy to solve if the system is balanced. However, if the system is unbalanced it can be quite difficult to derive the correct formula depending on how both wattmeters are connected. I figured if our students have been scratching their heads on this one, then a lot others probably have been too. Here are three new YouTube videos published today taken directly from the recording of last semester's live class. I hope this helps and please feel free to ask any questions in the thread. The full article where this information comes from can be found here: https://www.electricalpereview.com/3-steps-for-solving-the-two-method-wattmeter-problem/ ______ 3 Steps for Solving the Two Method Wattmeter Problem: Contents: Basic Rules, Circuit and Formula P = W1 + W2 (Two Method Wattmeter) Phasor Diagrams and Solving for W1 and W2 (Two Method Wattmeter) Shortcuts and Tricks (Two Method Wattmeter) 1. Basic Rules, Circuit and Formula P = W1 + W2 (Two Method Wattmeter) In Part 1 of the Two Method Wattmeter series, we are going to show you: 1. The three "rules" for using two wattmeters to measure the total power of a three-phase balanced or unbalanced circuit *For example: if the negative (-) voltage reference for wattmeter 1 (W1) is on C phase, then the negative (-) voltage reference for wattmeter 2 (W2) MUST also be on C phase. Rule #1 - The negative (-) voltage reference for both wattmeters MUST be on the same phase (both on A, B, or C). Rule #2 - The line current measured on each phase MUST be the same phase as the positive (+) voltage reference for each wattmeter! *For example, if the positive (+) voltage reference for wattmeter 1 (W1) is on A phase, then wattmeter 1 (W1) MUST ALSO measure the line current on A phase. Rule #3 - The positive (+) voltage reference for both wattmeters MUST NOT be on the same phase! *For example: if the positive (+) voltage reference for wattmeter 1 (W1) is on A phase, then the positive (+) voltage reference for wattmeter 2 (W2) MUST NOT be on A phase. 2. How to derive the two method wattmeter formula commonly seen in books depending on which phases the positive (+) and negative (-) voltage polarity for wattmeter 1 (W1) and wattmeter 2 (W2) are connected to: P3ø = W1 + W2 In the configuration that wattmeter 1 (W1) and wattmeter 2 (W2) are shown connected in this video, we can expand this formula into: P3ø = |VAC|·|Ia|·cos(θ-30º) + |VBC|·|Ib|·cos(θ+30º) 2. Phasor Diagrams and Solving for W1 and W2 (Two Method Wattmeter) In Part 2 of the Two Method Wattmeter series, we are going to show you: 1. How to draw the phasor diagram for both wattmeter 1 (W1) and wattmeter 2 (W2) depending on how each wattmeter is connected according to the three "RULES" from Part 1. The phasor diagrams will depend on which phases the positive (+) and negative (-) voltage polarity are connected to for wattmeter 1 (W1) and wattmeter 2 (W2). 2. How to easily derive the correct power angle (θ) for both wattmeter 1 (W1) and wattmeter 2 (W2) graphically using both of the phasor diagrams we set up. *Here's the trick! One of the line voltages being measured by either wattmeter 1 (W1) or wattmeter 2 (W2) depending on how they are connected will be NEGATIVE (CBA) SEQUENCE, and one will be positive (ABC) sequence. *Inside the cosine function in the power formula, one of the wattmeters will have θ MINUS thirty degrees while the other will have θ PLUS thirty degrees depending on how both wattmeters are connected: cos(θ-30º) cos(θ+30º) 3. Shortcuts and Tricks (Two Method Wattmeter) In Part 3 of the Two Method Wattmeter series, we are going to show you: 1. How to quickly identify which of the two wattmeters (W1 or W2) has the θ MINUS thirty degrees inside the cosine function, and which has the θ PLUS thirty degrees inside the cosine function WITHOUT taking the time to draw out the phasor diagrams. *It's extremely important to know how to draw both of the phasor diagrams (Part 2 in the Two Method Wattmeter Series) and how to derive the power formula commonly see in books (Part 1 in the Two Method Wattmeter Series) because in doing so you'll be able to answer just about any and every two method wattmeter question on the Electrical Power PE Exam. *HOWEVER! Time is really important during the exam because you only have a certain amount of time to answer each question. *Because of this, sometimes it is helpful to know how to QUICKLY identify which wattmeter the cos(θ-30º) and cos(θ+30º) terms belong to. 2. If the system is positive sequence (ABC), look for the negative sequence voltage. In a positive sequence (ABC) system: The A line voltage is measured from A to B (VAB) The B line voltage is measured from B to C (VBC) The C line voltage is measured from C to A (VCA) In the example circuit used in the video, wattmeter 1 (W1) is connected across A (+) to C (-). The line voltage that wattmeter 1 (W1) is measuring is the negative sequence C line voltage (VAC), NOT the positive sequence C line voltage (VCA). This means that the formula for the power measured by wattmeter 1 (W1) will have the 30º minus theta term inside the cosine function: In comparison, in the example circuit used in the video, wattmeter 2 (W2) is connected across B (+) to C (-). The line voltage that wattmeter 2 (W2) is measuring is the positive sequence B line voltage (VBC). This means that the formula for the power measured by wattmeter 2 (W2) will have the 30º plus theta term inside the cosine function: The wattmeter (W1 or W2) that has the 30º minus theta term inside the cosine function and the wattmeter (W1 or W2) that has the 30º plus theta term inside the cosine function always depends on how the wattmeters are connected. There will always be one wattmeter measuring a negative sequence line voltage, and a wattmeter that measuring a positive sequence line voltage. If the system is balanced, it does not matter which wattmeter formula has the 30º minus theta term inside the cosine function, and which wattmeter formula has the 30º plus theta term inside the cosine function since the line voltages magnitude and line current magnitudes will be equal. For example, if our example circuit used in the video is balanced then: |VCA| = |VBC| = |VL| and |Ia| = |Ib| = |IL| We can use this to simplify the two method wattmeter formula for a balanced system only: P3ø = |VCA||Ia|cos(θ-30º) + |VBC||Ib|cos(θ+30º) P3ø = |VL||IL|cos(θ-30º) + |VL||IL| cos(θ+30º) P3ø = |VL||IL|[cos(θ-30º) + cos(θ+30º)] __________________________ The full article where this information comes from can be found here: https://www.electricalpereview.com/3-steps-for-solving-the-two-method-wattmeter-problem/
  13. Hi @akyip it's mostly just minor revisions and corrections, the problems are still the same so you are good to go with the copy that you have.
  14. Most of the NCEES practice exam questions can be found pretty quickly using the search function. They've just about all been discussed:
  15. Studying for the October 2020 PE Exam? Our Practice Exam for electrical power is now available in print (hard copy) on amazon: https://www.amazon.com/dp/B088455H8J?ref_=pe_3052080_397514860
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