Tag: Free Book on AC
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9.6 Voltage Regulation
As we saw in a few SPICE analyses earlier in this chapter, the output voltage of a transformer varies some with varying load resistances, even with a constant voltage input. The degree of variance is affected by the primary and secondary winding inductances, among other factors, not the least of which includes winding resistance and…
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9.5 Winding Configurations
Transformers with Multiple Secondaries Transformers are very versatile devices. The basic concept of energy transfer between mutual inductors is useful enough between a single primary and single secondary coil, but transformers don’t have to be made with just two sets of windings. Consider this transformer circuit: Transformer with multiple secondaries provides multiple output voltages. Here,…
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9.4 Phasing
Since transformers are essentially AC devices, we need to be aware of the phase relationships between the primary and secondary circuits. Using our SPICE example from before, we can plot the waveshapes for the primary and secondary circuits and see the phase relations for ourselves: spice transient analysis file for use with nutmeg: transformer v1…
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9.3 Electrical Isolation
SPICE analysis of Electrical Isolation Aside from the ability to easily convert between different levels of voltage and current in AC and DC circuits, transformers also provide an extremely useful feature called isolation, which is the ability to couple one circuit to another without the use of direct wire connections. We can demonstrate an application…
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9.2 Step-up and Step-down Transformers
So far, we’ve observed simulations of transformers where the primary and secondary windings were of identical inductance, giving approximately equal voltage and current levels in both circuits. Equality of voltage and current between the primary and secondary sides of a transformer, however, is not the norm for all transformers. If the inductances of the two…
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9.1 Mutual Inductance and Basic Operation
Behaviors of Inductors wrapped around a Conductive Core Suppose we were to wrap a coil of insulated wire around a loop of ferromagnetic material and energize this coil with an AC voltage source: (Figure below (a)) Insulated winding on the ferromagnetic loop has inductive reactance, limiting AC current As an inductor, we would expect this…
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8.7 Summary of Filters
As lengthy as this chapter has been up to this point, it only begins to scratch the surface of filter design. A quick perusal of any advanced filter design textbook is sufficient to prove my point. The mathematics involved with component selection and frequency response prediction is daunting to say the least—well beyond the scope of…
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8.6 Resonant Filters
So far, the filter designs we’ve concentrated on have employed either capacitors or inductors, but never both at the same time. We should know by now that combinations of L and C will tend to resonate, and this property can be exploited in designing band-pass and band-stop filter circuits. Series LC circuits give minimum impedance at resonance, while parallel LC…
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8.5 Band-stop Filters
How to Create a Band-stop Filter? Also called band-elimination, band-reject, or notch filters, this kind of filter passes all frequencies above and below a particular range set by the component values. Not surprisingly, it can be made out of a low-pass and a high-pass filter, just like the band-pass design, except that this time we connect the two…
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8.4 Band-pass Filters
How to Create Band-pass Filter? There are applications where a particular band, or spread, or frequencies need to be filtered from a wider range of mixed signals. Filter circuits can be designed to accomplish this task by combining the properties of low-pass and high-pass into a single filter. The result is called a band-pass filter. Creating…
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8.3 High-pass Filters
A high-pass filter’s task is just the opposite of a low-pass filter: to offer easy passage of a high-frequency signal and difficult passage to a low-frequency signal. As one might expect, the inductive (Figure below) and capacitive (Figure below) versions of the high-pass filter are just the opposite of their respective low-pass filter designs: Capacitive…
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8.2 Low-pass Filters
By definition, a low-pass filter is a circuit offering easy passage to low-frequency signals and difficult passage to high-frequency signals. There are two basic kinds of circuits capable of accomplishing this objective, and many variations of each one: The inductive low-pass filter in (Figure below) and the capacitive low-pass filter in (Figure also below). Inductive…
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8.1 What is a Filter?
It is sometimes desirable to have circuits capable of selectively filtering one frequency or range of frequencies out of a mix of different frequencies in a circuit. A circuit designed to perform this frequency selection is called a filter circuit, or simply a filter. A common need for filter circuits is in high-performance stereo systems,…
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7.5 Circuit Effects
The principle of non-sinusoidal, repeating waveforms being equivalent to a series of sine waves at different frequencies is a fundamental property of waves in general and it has great practical import in the study of AC circuits. It means that any time we have a waveform that isn’t perfectly sine-wave-shaped, the circuit in question will…
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7.4 More on Spectrum Analysis
Computerized Fourier analysis, particularly in the form of the FFT algorithm, is a powerful tool for furthering our understanding of waveforms and their related spectral components. This same mathematical routine programmed into the SPICE simulator as the .fourier option is also programmed into a variety of electronic test instruments to perform real-time Fourier analysis on…