Power Angle

Check here

If the angle between active power and total power is you so called power angle, we normally call if power factor (for the whole frequency spectrum) or cos fi (in case we only look at the fundamental frequency).

Then the angle of the power factor can be bigger than 90°, but this means that your energy source becomes a energy load. It means that the direction of the energy path is reversed. You system that normally delivers the energy, now consumes energy.

Dear rudy.leurs@telenet.be,

I am just talking regarding to power angle and not power factor. You must know the difference.

MS has given some links and explained the subject.

Consider the physical significance of the two magnetic fields (rotor and stator)

When the two are aligned, the õ=0 and no power transfer takes place.

As the mechanical/electrical power is demanded (based on it is motor, generator) let us consider motor for simplicity, the rotor slows down abit. The angle between the new magnetic fields (the stator pulling the rotor) is what transfers the power.

Increase the drag (ie load on motor) and the angle automatically increases till it becomes maximum at 90^o.

Increase the load further - what happens? mechanical demand is more than the electrical power suppliable.

that could be one reason but a good explaination is given by my friend as below

I asked the same question in my EE lab years ago and my prof ran me through a series of questions and thought exercises for the answer. I'll see if I can briefly explain.

At 30 degrees power angle, if a system disturbance occurs and causes the generator's power angle to oscillate a little, it will settle out back at 30 degrees. As it goes to 31 degrees (sin 31 = 0.515, 3% increase) power flow to the external system increases. The added load on the generator increases torque on the turbine which brings the angle back toward 30 degrees, where it settles out.

Look at the same occurrence at 150 degree power angle. A bump occurs and the angle goes to 151. But power output drops about 3% so the turbine's torque can increase the power angle to 152 degrees then 153, 160 .... until it accelerates on past 180 and hopefully pulls back into synch at 30 degrees. Meanwhile, the currents have grown very large because the two voltages went 180 out of phase.

What we are looking for in a system is a stable operating point where the natural tendency in response to a disturbance is a return to the original operating point. It's like balancing a broom on end or hanging from a hook. Both hold the weight directly in line with the support point, but when the broom is bumped and starts to swing, gravity helps the hanging broom settle out and accelerates the balanced broom to the floor.

It is what I needed to know.

when torque increase ,y the angle shud settle back at 30 degrees?....wat is relationship between power angle and torque of gen?