Which is better for creating DC power, a Generator or an Alternator?

[karim102]

Hi ,
How are you? I am a again. I've question about what is diffenent between Ganerator D.C and Alternator. I know the Alternater always give us A.C but we use rectifier when we want to D.C, but what is the better Generator D.C (it is one Machine) Alternator, when we want to D.C? because I think the Generator is better when we want to D.C because it is one machine. and it is so cheap then Alternator.

Thanks
I appreciate it :!)

 

[ranger]

I've question about what is diffenent between Ganerator D.C and Alternator.

While DC generators work on the same general principle of electromagnetic induction, their construction is not as simple as their AC counterparts.

http://www.ibiblio.org/obp/electricCircuits/AC/02002.png
That is a basic diagram of a alternator. BAsically the switching of the polarities of the voltage and direction of the current are changed because of the chaning magnetic field.

http://www.ibiblio.org/obp/electricCircuits/AC/02003.png

That is a basic diagram of a DC generator. The coils are the key difference. In order for a DC generator to produce constant voltage, rather than brief pulses of voltage once every 1/2 revolution, there are multiple sets of coils making intermittent contact with the brushes.

The relative simplicity of an alternator translates into greater reliability and lower cost of manufacture.

 

[gschjetne]

A rectifier bridge isn't very complicated, nor is it expensive. Possibly even less so than a set of commutators.

Also, my Private Pilot's License textbook offers the very scant explanation that alternators are preferred in light aircraft over generators because they generate a higher voltage at lower RPMs.

But I don't see why. Faraday's law still holds!
$$\varepsilon = -N \frac{d {\Phi}_B}{d t}$$

Besides, the book is full of typos. It's a miracle I passed the exam.