Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [electric-machine]

Electrical Machines are Electro-Mechanical energy converters. They maybe classified into motors (electrical -> mechanical) and generators (mechanical -> electrical).

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How do I fix the speed of a generator?

If I need to generate power at a specified frequency, then I need to make sure that the rotor of the generator rotates at a specified speed (rpm). But when I am rotating it with steam or water how do I control this speed? It seems to me that the…
praveen kr
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Electrical Machines based on Electric Fields

Our teacher asked us this question during the lecture for Power Electromagnetics. We know that Electric Fields and Magnetic Fields are easily transformable into one another. And they are used greatly in various systems. He asked us why is it that…
Digvijay Gusain
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Isn't current flow a wrong term?

In most text books and other electronics material it's said current is flowing through the circuit. Isn't this wrong? As current is flow of charge. Is there anything such as flow of flow of charge?
Ali Khan
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High voltages Transmission lines?

I am having a doubt in why are the transmission lines are sent at a very high voltages? I also went through quite a few sources which said that it is to decrease the losses in the lines. BUt I am not quite satisfied with the solutions, can somebody…
IamDp
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In an electric machine, does the force act on the copper conductors or on the iron and why?

My question arises from the following reasoning: Starting from the basic explanation that a force acts on a current-carrying conductor in a magnetic field, I realized that, more concretely in electrical machines, since the conductors are embedded in…
PortaL
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Why is slip necessary in an Induction motor?

Why should the rotor of a 3-phase induction motor not rotate at synchronous speed?
ilyas
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Electricity consumption of electrical machines - why do they consume electricity when they are not turned on?

The question is, why do electrical machines consume power when they are not turned on (they are plugged into an outlet)? Also, suppose there is a seven-port USB hub with AC power. Is the power consumed by the hub always the same regardless of how I…
AER
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Doubt about the volume of the air gap in an electrical device

So for the following device: I'm trying to figure out the torque. To do that, I need the area of the gap. In the solution, it says that the gap volume is: $$2gh(r_1+0.5g)\theta$$ But the part of \$ r_1+0.5g \$ is really confusing me. I'm not…
Miguel Duran Diaz
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Dry, wet and free voltage contact?

I would like to ask about three kinds of electrical contacts: dry, wet and free voltage. What is the difference between them?
Adban
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What is meant by front and back pitch of an armature winding?

I searched the internet for these definitions and found a common definition in all websites: Back Pitch- A coil advances on the back of the armature. This advancement is measured in terms of armature conductors and is called back pitch. It is…
jNerd
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Electric shock from laptop due to capacitive coupling?

If a person touches an exposed wire (the wire has a ground-prong) on the 20V side of a power cable while barefoot, I heard that it is possible to receive a shock of higher than 20V due to capacitive coupling. Could anyone explain how this is…
minusatwelfth
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Why duplex lap winding has twice as many current paths as simplex lap winding?

I found the statement of question on page 346 in the book "Electric Machinery Fundamentals, fifth edition" written by Stephen J. Chapman. When I searched for how duplex lap winding looks like, I found the figure in this link:…
8cold8hot
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How was ceiling fan speed controlled before the invention (or availability) of Triac?

I am interested to know about the circuit diagram of the ceiling fan regulators of the old days (when Triacs were not available). I have searched on google but all of the results were related to SCR. I heard that they used resistors but never got…
Sadat Rafi
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If a high rpm motor is run at lower rpm, will it produce more torque?

I did the following calculations: Max current = 1.2A, Max voltage = 12V Then power = 14.4 watts = 0.019hp Rpm = HP * 5252 ÷ torque I need a torque to 2kgf-cm = 0.144 lb-ft Gives rpm= 698. Thus this means if I put load(mechanical) on the motor, it…
Aether
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How do I modify a DC electric generator to get the same power at a lower speed?

This will be a theoretical question. Suppose that I have a DC generator, and I'm getting 300VA power from it when it rotates at 2000rpm. I want to make it run at a lower speed of about 700rpm, and I still want to get 300VA power from it. What…
hkBattousai
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