Armature and field winding of Generator

[psvtrajan]

why can we make both armature winding and field winding as a rotor?

 

[Averagesupernova]

Question makes little sense to me.

 

[Jeff Rosenbury]

You can.

But why?

I suppose contra-rotating armatures would look cool for a Hollywood sci-fi FX.

 

[Babadag]

Do you mean, the poles on the rotor and the armature on the stator? This is a synchronous generator. You need a rectifier in order to get d.c.

Or do you mean double-rotor d.c. generator ?However this is a synchronous generator too.

See-for instance-

http://www.researchgate.net/publication/251971296_A_constant-frequency_double-rotor_generator_for_wind_power_application

 

[anorlunda]

I think the OP is asking about building the generator inside out. With the field winding on the stator and the armature on the rotor.

Yes, that will work. Either arrangement produces the same relative motion.

However it will, be very difficult to transfer large amounts of power to or from the rotor, via slip rings or commutators. Typically, power to the field is much less than power to/from the armature.

 

[anorlunda]

Actually, I can imagine a highly contrived application.

Consider a forge making cannon barrels. A mandrel penetrates the barrel while forging hammers pound the outside, and the whole thing rotates. We could make a resistance heater for the mandrel powered by the armature of a generator also part of the rotating mandrel. The field winding would be on tha stator.

The key feature is that the load power is consumed on the rotating part. Other examples are hard to think of.

 

[psvtrajan]

No both the winding are rotating. i.e there is no stator part

 

[anorlunda]

No both the winding are rotating. i.e there is no stator part

As long as they have rotary motion relative to each other, what I said in post #5 applies. It can work as a generator or a motor, but if you need to transfer large powers to non-rotating circuits, it will be difficult.

 

[Averagesupernova]

I think the OP is asking about building the generator inside out. With the field winding on the stator and the armature on the rotor.

Yes, that will work. Either arrangement produces the same relative motion.

However it will, be very difficult to transfer large amounts of power to or from the rotor, via slip rings or commutators. Typically, power to the field is much less than power to/from the armature.

Automotive generators from days gone by always had the rotor as the winding that supplied the actual charging current. This is what you referred to right? Admittedly they could not come close to competing with modern alternators.

 

[psvtrajan]

No I'm asking for double rotor generator.

 

[Jeff Rosenbury]

There was an aircraft engine where the pistons rotated back in the early days of flight. I'm not sure why, possibly cooling?

Perhaps rotating both windings could save copper by increasing the cooling potential?

I can think of better solutions. We don't see many rotating pistons anymore.

 

[Averagesupernova]

The rotary engines that had the whole block that turned and the crank stationary had no vibration due to reciprocating parts. They could turn easilyin one direction but had to make very wide turns in the opposite direction.

 

[anorlunda]

Is this what you mean?

https://en.m.wikipedia.org/wiki/Doubly_fed_electric_machine