Hello,

Although there is a lot of information on the Magnetic Field Coil power supply design, I thought that I would try to summarize and explain how it works in layman's terms, and answer questions as I present ideas about the principles that are used to operated it. So questions are welcome, but I ask that they be directed only at what I have presented so far.

*Problem: High power amplifiers require heavy, expensive and inefficient power supplies.*

*Answer: Design an affordable, lightweight and efficient power supply.*

Bob's idea: What if I was able to control the AC line voltage into the power transformer so that a power supply was only given just enough power to respond to demand? If that were possible, I wouldn't need a large transformer, and the amp would have more power when it needed it, and thus it would not waste it.

**Principle One: AC line voltage**

AC stands for *alternating current*. In the US, the standard voltage is 120V at 60 cycles per second. AC line voltage is a *sine wave* that changes direction (polarity) 120 times per second.

Shown above is one cycle, measured in Hertz (Hz). This we call the *frequency* of the signal, or* cycles per second*. So 60 cycles per second is 60Hz (notice *one* cycle has a positive *and* negative polarity swing). Notice the *rms* line - AC line voltage actually peaks at about 160V, and therefore 120V is the effective rating, or Root-Mean Square rating (peak voltage x .707). This is the voltage used for calculating the 'realistic' power of an AC signal.

The line though the center of the signal is the ground potential, or ZERO volts. Notice that the voltage, as a function of time, increases to maximum, decreases, passes through 0, then changes direction and increases negative to a maximum, then decreases to 0 again and repeats. We call this a *periodic signal -* that is, a signal that repeats itself over and over with a predicable regularity. Obviously, AC line voltage is a periodic signal (at least it should be!).

A word about Voltage, Current, Resistance and Power...

**Voltage** is potential difference, measured in Volts, which is *Energy per unit charge*. It is also knows as Electromotive Force. What does that mean? It means that voltage represents the presence of electrical energy. Large voltage means the presence of a large amount of energy with respect to another *potential, *which is usually ZERO or Earth Ground. All bodies, and all mediums have some charge, so there is really no such thing as a zero charge reference. We use the Earth itself as a zero reference because it is relatively stable and does not change much as a whole. So to say something is at 100 Volts, it is understood to be referenced to Earth Ground. Sometimes it can reference the *common* of a circuit, but whatever the case, 100 Volts means a *potential difference* between two points or bodies. Voltage doesn't do any work - it is simply the measure of the *potential* to do work. This is important to understand.

**Current** is *unit charge per second*. Notice that current, unlike voltage, is a per second measurement. That is, current indicates a system that is changing or flowing. Current is measured in Amperes, or Amps, and is the amount of charge we see through one ohm of resistance at one volt potential during one second. Therefore, when a potential difference exists, there can be a current, a flow of that energy, through a medium like a wire. *No potential difference, no current.* So current is energy that is doing work.

**Resistance** is the tendency of a medium to resist the flow of electrons (charge) from one potential to another. Resistance is measured in Ohms. Notice that resistance directly affects current - in that current is the flow of energy while resistance is what *limits that flow*. If there were no resistance between two potentials, there would be infinite amount of energy possible to flow. If there is near infinite resistance, then there is no current (open circuit), only voltage (potential *difference*). Understanding that 1 Volt pushes 1 Amp though 1 Ohm in 1 second is the basis of Ohm's Law and how electronics work.

**Power** is the product of current and voltage, and is measured in Watts. A watt is a real SI unit of work, which is equal to one joule per second, or the amount of work (heat) generated by one volt through one ohm of resistance (one amp of current).

These relationships can be calculated and/or predicted in systems using Ohm's Law. V is ElectroMotiveForce (Volts), I is Current (Amps), and R is Resistance (Ohms). 'E' is normally in place of 'V' (EMF), but we'll use 'V' for Volts just for clarity for beginners:

You must have a basic understanding of these concepts. Meditate upon them.

"The greatest leader is not necessarily the one who does the greatest things. He is the one that gets the people to do the greatest things." – Ronald Reagan

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