ch10 - Electricity And Electronics Fundamentals TECH 175...

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1 Electricity And Electronics Fundamentals TECH 175 Fall Semester 2007 Chapter 10 Generators 3 Outlines • Explain how mechanical energy can produce electrical energy • Faraday’s law and Lenz’s law • Difference between direct current and alternating current • Construction and function of a generator • Types of generators 4 Electrical Energy from Mechanical Energy • Faraday’s experiment • Moving a conductor through a magnetic field induced a voltage in the conductor 5 Faraday’s Experiments 6 Faraday’s Experiments (cont’d)
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2 7 Electromagnetic Induction • Faraday’s Law – Voltage is induced in a circuit whenever the flux linking the circuit is changing – Magnitude of voltage is proportional to rate of change of the flux linkages with respect to time 8 Electromagnetic Induction • Lenz’s Law – Polarity of the induced voltage opposes the cause producing it 9 Induced Voltage and Induction • If a constant current is applied – No voltage is induced • If current is increased – Inductor will develop a voltage with a polarity to oppose increase • If current is decreased – Voltage is formed with a polarity that opposes decrease 10 Induced Voltage per volt lines flux of number second per s revolution lines flux magnetic voltage induced 10 8 × = × Φ = N E 11 DC vs. AC •DC – Direct current (dc) flows in only one direction – Pure direct current • Current is constant – Pulsating direct current • Current is not constant •AC – Alternating current (ac) flows in alternating directions within a given time period 12 DC Voltage
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3 13 DC Voltage 14 Sinusoidal AC Waveforms • A sinusoidal ac waveform starts at zero – Increases to a positive maximum – Decreases to zero – Changes polarity – Increases to a negative maximum – Returns to zero • Variation is called a cycle 15 Sinusoidal AC Waveforms 16 Sinusoidal AC Waveforms 17 Symbol of AC Voltage Source 18 Sinusoidal AC Current
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4 19 Sinusoidal AC Voltage and Current 20 Generator • A generator is a device that converts mechanical energy into electrical energy • ac voltage is generated by rotating a coil of wire at constant angular velocity in a
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ch10 - Electricity And Electronics Fundamentals TECH 175...

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