Power System Stability

I recommend that you review the Steinmetz equivalent circuit for induction motors. This principle still leads to new research.

There's nothing wrong with your homework statement, it describes how power is transferred from a synchronous generator to a synchronous motor. There are two things missing though, an understanding of the sign convention regarding power entering and leaving a generator buss, and whether your motor is over or under excited.

It's time for you to review your "Basic Electric Machines"course notes, concentrating on the Power Angle topic, where you will find the basic power flow equations.

Hint: Real power always flows from the machine with the higher power angle to the one(s) with the lower angle(s), Reactive power always flows from the machine with the higher terminal voltage to the machine(s) with the lower terminal voltage(s).

akp: Check out the book by Edward Huges entitled "Electrical Technology", fourth edition, chapter 17, " Characteristics of Synchronous Generators and Motors". The rotor magnetic field and the stator rotating magnetic field interact in such a way so as to cause the rotor to lock to the rotating magnetic field of the stator (synchronous speed) and run in synchronous speed, when the machine has reached nearly full speed.

triniboy, I agree with all of your statements except "run in synchronous speed, ... nearly full speed" Synchronous motors ARE "locked in" at full speed which is the same as synchronous speed. If there is any slip (after the start cycle) the circuit protection device usually/should trip. By the way, that is a very good reference book. I don't intend to nitpick but it may be slightly confusing for some.

No. (I wish CR4 had a face palm smiley.)

Here is the torque curve for various induction motors.

This came from this site. You should notice that if there is no slip between rotor and and stator then there is no torque produced, at all. The rotor bearings alone produce some drag that must be overcome so torque must be produced. Now depending on the drag of the load the motor is driving the slip will be even more.

I agree with Rixter. I think since the stator current in generator armature it is the induced current in turn its magnetic field, with the rotor magnetic field, will produce a "reaction "torque which opposes to the rotor effort to go forward. How big is the current so big is the stator magnetic field lag. In the synchronous motor the stator current is the leader and pull the rotor on and so how big will be the rotor load so big is the rotor lag.