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Engineering Talks


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Everything posted by DrD

  1. Power factor is the cosine of the angle between the voltage and the current. It is the third factor in the product that expresses the power, P = V*I*cos(phi) where phi is the phase angle. DrD
  2. Real power is just what it says, power as in work done per unit of time. In electrical systems, the real power is calculated as Preal = V*I*cos(phi) where V = voltage I = current phi = phase angle between current and voltage Reactive power is Preact = V*I*sin(phi) I've never heard the term "apparent power" but I suspect what you mean is what I know as Volt-Amperes = V*I The real power is the in-phase part of the volt-ampere product while the reactive power is the out-of-phase part of that product. DrD
  3. Ths is done to reduce eddy current losses by preventing current flow perpendicular to the laminations. The laminates are electrically insulated from each other (usually by varnish) which blocks current flow while allowing magnetic flux to flow freely. DrD
  4. This process is called "field weakening" and it was used for speed control on the ancient rolling mill where I worked long ago. As the field current is reduced, flux must be cut more rapidly to maintain the back EMF. The only way this can happen is for the rotor to turn more rapidly, thereby cutting more flux per unit of time. DrD The term "linear machine" seems ambiguous to me. I think you intend to describe an electrical machine (motor) described by linear differential equations. The term can also be used to describe an electric motor for which the moving element translates rather than rotates. For a translating induction machine, the usual acronym is LIM, Linear Induction Machine. Such machines can also be built in synchronous form, known as LSM, Linear Synchronous Machines. The linear machines of this sort are being used to launch aircraft from aircraft carriers. DrD
    I hope that a great many folks will download this file. It is better than that previously posted, and probably my last effort. It is not yet available at Lulu.com, but I hope to eventually make that happen. It seems inappropriate to rate my own book, but it is required by the website. DrD
  5. Now that is an interesting question! Do you mean Ampere's circuital law? or Do you mean Ampere's force law?
  6. Version 1.0.0


    This is the second edition of an engineering textbook first published by John Wiley & Sons in 1988. It is offered free to all who want a copy. Simply pass the PDF file along to anyone who can use it. You will be pleasantly surprised at the problems that you can work if you adopt the methods of this text. It does require some math and computer capability.
  7. That is a GenSet, and it is at least as much mechanical as it is electrical. Almost 50 years ago, I worked for a company that put together such packages, IC engines with any sort of driven machine. Generators were the most common, but we also powered pumps, air compressors, fans, whatever. It was a great place to work, with lot of very real, very serious, engineering challenges! DrD
  8. TDC is Top Dead Center BDC is Bottom Dead Center For an engine with no cylinder center line offset, the cylinder center line passes through the crank axis of rotation. When the piston is farthest away from the crank axis, this is the TDC condition. When then piston is closest to the crank axis, this is the BDC condition. The term "dead center" refers to the fact that pressure acting on the piston in a dead center position produces no torque on the crank and hence no ability to move a load. The term derives from the era of steam power when single cylinder engines were very common. DrD
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