Electrical PE Exam Questions And Answers With Latest Updates

Inductor impedance equation Correct Answer: Z = j*w*L How can a transformer, motor, or generator be saturated? Correct Answer: The voltage/frequency ratio is altered. For example, this happens when excessive voltage is applied to the primary side or the frequency is too low. What are some sources of triplen harmonics? Correct Answer: Electronics, CFL lamps, electronics dimmers, etc. What are the effects of triplen harmonics on an electrical system? Correct Answer: 1. Neutral overloading 2. Electrical equipment (bus bars, transformers over-heating) 3. Eddy current losses (proportional to square of frequency) How are triplen harmonics mitigated? Correct Answer: Detuned filter or active harmonic filter. Capacitor impedance equation Correct Answer: Z = (-j)/(w*C) What is conductance? Correct Answer: Inverse of resistance RMS (root means square) equation Correct Answer: RMS = Max/sqrt(2) Parallel resistor Equation (only 2) Correct Answer: (R1*R2)/(R1+R2) Convert sin(wt) to cosine form Correct Answer: cos(wt-90) Is a positive reactive power inductive or capacitive? Correct Answer: Inductive Is a negative reactive power inductive or capacitive? Correct Answer: Capacitive If the power factor is lagging, the _______ lags the _______ Correct Answer: current, voltage If the power factor is leading, the _______ leads the _______ Correct Answer: current, voltage Why is reactance required in a system? Why not have unity power factor? Correct Answer: Reactance is required for transformer action in transformers and generators (inductive components consume reactive power) and to keep bus voltages at their required values. Power factor equation relating true power and apparent power Correct Answer: pf = P/S Power factor equation relating the voltage and phase angles Correct Answer: pf = cos(theta_Vtheta_I) Equation for apparent power (S) based on real power (P) and reactive power (Q) Correct Answer: S^2 = P^2 + Q^2 Continues...