Residual magnetism in shunt generator reverse F1F2

[jaus tail]

Hi,
I'm not able to understand how reversing Field terminals will help build magnetic flux in dc shunt generator
Have drawn diagrams below.
In 1st case machine doesn't generate as the flux opposes residual flux, so I reverse F1, F2 and draw below diagram...

But in second case the direction of current will also change as the flux has changed its direction. So by right hand rule, emf also changes sign. So again the field flux is same as right to left. How does this work? Do I change the direction of rotation of prime mover?

 

[NascentOxygen]

Can you provide the page where you have seen this technique described? It might give a clue to what is going on.

What are F1,F2?

 

[jaus tail]

The description is:
The small voltage due to residual magnetism should circulate current in field coils in a direction to produce flux aiding the residual flux. If the field connections are incorrect, the flux produced by small field current opposes residual flux and generated voltage becomes zero. This trouble can be remedied by reversing field connections w.r.t armature terminals.

There isn't any diagram or more. I drew the diagram myself.

 

[jaus tail]

Okay got it. At first field current is zero. Residual flux is there. This causes Eg and also Ia. This also gives field current. Now if field flux opposes residual flux then generator goes to zero voltage as flux has fallen.
But if I reverse field. Again at first field current is zero. Residual flux is there. This causes Eg and Ia. This gives field current. But now it's opposite so it aids residual flux.

 

[NascentOxygen]

The description is:
The small voltage due to residual magnetism should circulate current in field coils in a direction to produce flux aiding the residual flux. If the field connections are incorrect, the flux produced by small field current opposes residual flux and generated voltage becomes zero. This trouble can be remedied by reversing field connections w.r.t armature terminals.

There isn't any diagram or more. I drew the diagram myself.

It's saying if you connect the field the wrong way it won't work. To fix this, connect it the right way and it will work.

Imagine a permanent magnet generator. You decide to add an electromagnet to strengthen the field. There are two ways to merge the fields: additively and subtractively. The prime mover's rotation remains unchanged.