Difference Between DC and AC Generators (1 Viewer)

[Stopsign]

There are a number of questions I need to have answered before the exam.


1.Difference between DC and AC genertors? (Split-ring and slip rings?)

2.Do motors and generators have the same structure?

3.Disadvantages of AC (electric chairs? dangers?)

4.Am I right on this one?...Transformers step up the voltage once they leave the power station and are carried away to minimise energy loss and maximise voltage but are stepped down to 240v for homes.

 

[zeek]

1. Yes the main difference between simple AC and DC generators is the commutator. AC generators use the slip ring, which is two closed rings, each connected to either the input or output. DC generators use the split ring which ensures that the currect is "restarted" every 180 degrees of rotation so that you get it going in one direction only. You should note that the only reason you get DC current from DC generators is because they have the split ring commutator.

2. Yes, they do have the same structure. The only difference is that with motors, you supply energy to do work, however, with generators, you use another form of energy (such as steam or running water i.e. kinetic energy) to allow the rotor to rotate (rotational energy) and then for it to produce an EMF (electrical energy)

3. Hmmm.... i guess the only disadvantage of AC that i can think of would be the safety issues that go along with it. AC current is *i think* up to 5 times for deadlier than DC current.

4. Yes you are correct. Power stations use a step-up transformer to decrease the current and increase the voltage so that there is minimal resistance. So by decreasing the current, we decrease the number of collisions that the electrons experience through the transmission lines and hence decrease energy loss. In the suburbs, they use step down transformers so that the voltage can be decreased, and at the same time, the current increases.

 

[Stopsign]

Thanks Rev.

I know that a DC motor/generator reverses current every half-turn to keep it rotating in the same direction but how does an AC one work? What are the slip-rings for? What do the negative voltages mean? (Sine curve)

 

[simbim21]

the slip rings in a generator are simply a point of contact between the coil and the external circuit. That is, it transfers the electrical energy generated to where it is needed. The output voltage produces a sine curve because as the coil rotates, it goes from a positive maximum when it is parallel to the field to a minimum when perpendicular and again to a maximum but current is in the opposite direction. the negative sign simply indicates direction.

hope that helps

 

[helen_mac]

an advantage of a DC generator is that they can be made with many coils wrapped around the armature, the brushes only make contact with the commutator bars inducing the greatest emf at a time so the voltage produced is smoother. AC fluctuates between maximum and zero

hope that helps

 

[NightShadow]

btw the way...DC is better for electric chairs..cause the AC current causes your muscles to fibrillate like when you hold a wire in AC your hand opens and closes rapidly... (DONT TRY THIS)

while DC it's just continuous and you hand closes..and stAYS CLOSED if you know waht i mean

so AC looks bad in death, but DC is the more efficient killer