What will happen when a running synchronous machine power angle exceeds 90 degrees?
If the load angle of the machine reaches 90°it has reached its maximum power output for the strength of the magnetic fields. If the power input to the machine pushes the rotor past the 90°position the retarding forces on the shaft start to decrease not increase. The rotor will start to accelerate.
What happens if you increase the load on a synchronous motor?
If the load on the motor increases, the torque angle α also increases (i.e., rotor poles lag behind the stator poles by a greater angle) but the motor continues to run at synchronous speed. The increase in torque angle α causes a greater phase shift of back EMF Eb with respect to supply voltage V.
What happens to the speed of a synchronous motor if the load is increased?
The load on the shaft is increased. The rotor slows down momentarily, as it required some time to take increased power from the line. In another word, it can be said that even if the rotor is rotating at synchronous speed, the rotor slips back in space because of the increase in the load.
What is power angle in synchronous motor?
Power Angle Curve of Synchronous Machine is the graphical representation of electrical output with respect to the power angle. As we know, power angle is also known as load angle, therefore it can be said that this curve is graphical representation of electrical output of generator with respect to load angle.
What is the effect of increasing the load of a synchronous motor running with normal excitation?
When a synchronous motor is operating with normal excitation, with the increase in load: The motor continues to run at a synchronous speed as it is a constant speed motor. The torque angle δ increases.
Why does the synchronous motor keep on rotating at low load with synchronous speed even after withdrawal of excitation?
Suppose the motor is running at synchronous speed and suddenly the rotor DC excitation is put off. Thus the rotor conductors will lose magnetic polarity. But due to inertia it will continue to rotate at synchronous speed for some time.
What happens when the load on a synchronous motor is increased?
Thus, if the load on a synchronous motor is increased the following points are considered which are given below. The motor continues to run at synchronous speed. The torque angle δ increases. The excitation voltage E f remains constant. The armature current I a drawn from the supply increases. The phase angle ϕ increases in the lagging direction.
What is power angle and torque angle in synchronous motor?
For the case of synchronous motor, the angle is called torque angle and the rotating field lags the stator field in this case. Power angle: For a generator, the power angle is the difference between the generator induced voltage and the generator terminal voltage.
What happens to the torque angle when the load is increased?
As the load is increased, the torque angle δ also increases until the condition arises when the rotor is pulled out of synchronism and the motor is stopped. Pull-out torque is defined as the maximum value of the torque which a synchronous motor can develop at rated voltage and frequency without losing synchronism.
What is load angle in a synchronous generator?
As discussed earlier in this post, load angle is the angle between the field flux and the resultant air gap flux. This means, as the mechanical power input to the synchronous generator is increased through prime mover, the field poles will be dragged ahead of the stator pole or flux. This in turn will increase the load angle.