Recent content by jitznerd

  1. J

    Voltage Waveform for 3rd and 5th Harmonics with 120Hz Fundamental at 20ms

    Thanks for that So would it be along the lines of: V=141.1sin(240πt)+28.3sin(720πt)+14.1sin(1200πt-1.2) How I am working out the voltages is using above formula, This is how I worked out first section but pretty sure I am going around this the wrong way 141.1sin = .268 240 x π x...
  2. J

    Voltage Waveform for 3rd and 5th Harmonics with 120Hz Fundamental at 20ms

    Homework Statement An a.c. voltage, V, comprises of a fundamental voltage of 100V rms at a frequency of 120Hz, a third harmonic which is 20% of the fundamental, a 5th harmonic which is 10% of the fundamental and at as phase angle of 1.2 radians lagging. 1. Write down an expression for the...
  3. J

    A.C. Voltage waveforms and harmonics?

    Hi Im stuck on the same question. I've been using 141.4sin(2pi x f(120) x 0.02), which gives me 9.41v 28.3Sin(2pi x 360 x 0.02) = 21.45v 14.1sin(2pi x 600 x .02 - 1.2) = 18.08v Then added these up to give combined voltage at 20ms of 48.93v This is obviously a diffenrent answer to answers...
  4. J

    Transformer Primary and secondary currents

    Homework Statement A single phase transformer has the following rating : 120kVA. 2000v/100v, 60 Hz with 1000 primary turns. Determine: a.Secondary turns b.The rated primary and secondary currents Homework Equations Vp/Vs = Np/Ns The Attempt at a Solution a. I have used...
  5. J

    Calculating time in which flux changes

    Yeah I thought 8 seconds seemed a long time, that's what made me query if I had gone about it right. The question is typed exactly as I have been given with those units, then I have used what I think is Faradays law: E (volts) = N (number of turns) x change in flux (Webers) / Time (s)...
  6. J

    Calculating time in which flux changes

    1. Homework Statement [/b] If the magnetic flux linking all the turns of a 50 turn coil changes from 10mWb to 20mWb and induces an emf of 62.5V in the coil, calculate the time over which the flux changes. Homework Equations e=Nd x change in flux / dt The Attempt at a Solution Not...
  7. J

    How Do You Calculate the Radius of a Variable Capacitor's Plates?

    Thanks for that gneil Yeah the n is for the plates. Am I right in assuming the answers are in meters^2 for the first part? Could you also tell me if everything looks ok on the remaining answers. Many thanks
  8. J

    How Do You Calculate the Radius of a Variable Capacitor's Plates?

    Homework Statement A multi plate variable capacitor has 4 pair of plates. The plates, when closed, are separated in air by 0.01mm and a capacitance range of 10 to 400pF. a) Estimate the required radius R of each plate. b) The capacitor is set to maximum 400pF and is charged to 10V...
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