So how would this correspond to load imbalances on a 3-phase generator?

Lets say for example, the L1 phase is loaded 4x as heavily as L2 and L3.

If one of the phases is heavily loaded (say 4x) then basically it is an unbalance load condition for a 3 phase generator. In this case the negative sequence components of 3 phase currents comes into picture.

The negative sequence components of the stator currents develop a revolving magnetic field which is in opposition to the original direction of the generator revolving magnetic field. for e.g. if the direction of the original revolving magnetic field was clockwise, then the direction of the revolving magnetic field developed by the negative sequence components of stator current will be in anti-clockwise direction.

This oppositely revolving magnetic field (due to -ve sequence stator currents) superimposes itself over the original generator magnetic field resulting in a braking action on the generator rotor causing it to slow down or stall completely. Since the magnitude of this braking current is assumed to be very large (say 4x) the braking action will be extremely destructive for the generator.

Speaking of voltages, the 3 phase phase voltages will become highly unbalanced w.r.t the star point (neutral wire) of the 3 phase generator. If L1 is considered to be heavily shorted circuited, then L2 & L3 will act as an unbalanced 2 phase, 3-wire system.

Please Note:- The concept of sequence components of 3 phase currents is a purely theoretical concept developed only to simplify unbalanced 3 phase power system problems. It will be very difficult to visualize it and prove it to you practically.
Hope i have grasped your doubts correctly. If you want a more detailed explanation, please let me know!

 

If one of the phases is heavily loaded (say 4x) then basically it is an unbalance load condition for a 3 phase generator. In this case the negative sequence components of 3 phase currents comes into picture.

The negative sequence components of the stator currents develop a revolving magnetic field which is in opposition to the original direction of the generator revolving magnetic field. for e.g. if the direction of the original revolving magnetic field was clockwise, then the direction of the revolving magnetic field developed by the negative sequence components of stator current will be in anti-clockwise direction.

This oppositely revolving magnetic field (due to -ve sequence stator currents) superimposes itself over the original generator magnetic field resulting in a braking action on the generator rotor causing it to slow down or stall completely. Since the magnitude of this braking current is assumed to be very large (say 4x) the braking action will be extremely destructive for the generator.

Speaking of voltages, the 3 phase phase voltages will become highly unbalanced w.r.t the star point (neutral wire) of the 3 phase generator. If L1 is considered to be heavily shorted circuited, then L2 & L3 will act as an unbalanced 2 phase, 3-wire system.

Please Note:- The concept of sequence components of 3 phase currents is a purely theoretical concept developed only to simplify unbalanced 3 phase power system problems. It will be very difficult to visualize it and prove it to you practically.
Hope i have grasped your doubts correctly. If you want a more detailed explanation, please let me know!

It is an interesting discussion. I cannot visualize what you speak of. All attempts to google come up with only 'imbalanced' 3 phase loads, where all 3 phases are imbalanced. I refer to a situation with only one phase loaded and the other two not.

Perhaps you have already thought of this and I am only unable to visualize it. Can you reference me to a URL describing what you said and how it relates to my inquiry? I didn't have much luck finding anything informative enough.

Thanks

 

Do not worry about the sequence components part….it is a purely theoretical concept and has no practical implications. Sorry! sometimes I do tend to put in a lot of unnecessary theoretical stuff.

I refer to a situation with only one phase loaded and the other two not.
Perhaps you have already thought of this and I am only unable to visualize it. Can you reference me to a URL describing what you said and how it relates to my inquiry? I didn't have much luck finding anything informative enough.
Thanks

The situation wherein only one phase of a 3 phase generator being loaded is again a classic example of a heavily imbalanced 3 phase power system. The case is similar to a 3 phase Xmer or generator whose L2 & L3 lines have become open due to, say, blown fuses on both the lines.

The problem which you have put forth is basically textbook material pertaining to electrical machines.
I suggest you google ‘Single-phasing of 3 phase transformers or generators’ or refer textbooks on electrical machines by reputed authors or technical books by Mcgraw Hill publications.……. you should be able to find some theory pertaining to your problem.

But are you looking at the mechanical effects of your abnormal conditions or an electrical one, please clarify.