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What happens to the V-curve when a synchronous motor is loaded?
V curve is a plot of the stator current versus field current for different constant loads. If now, the field current is increased further, the armature current increases and the motor starts operating as a leading power factor. …
What happens to a synchronous motor as its field current is varied?
Explain, using phasor diagrams, what happens to a synchronous motor as its field current is varied. When a synchronous motor excitation is changed then its operating power factor and armature current will changes.
What do V curves represent in synchronous motor theory?
V-curve of a synchronous machine shows its performance in terms of variation of armature current with field current when the load and input voltage to the machine is constant.
What is the necessity to draw the V and inverted V curves of a synchronous motor?
As against this, if the power factor (cos ф ) is plotted against field current (If), then the shape of the graph looks like an inverted V. Such curves obtained by plotting p.f. against If, at various load conditions are called Inverted V-curves of synchronous motor. These curves are shown in the Fig: 2.27 (b).
What does V-curve mean?
In power engineering & electrical engineering, V curve is the graph showing the relation of armature current as a function of field current in synchronous machines keeping the load constant.
Which increases in load the speed of synchronous motor?
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 Ef remains constant.
What is the V curve of a synchronous motor?
The graph drawn between armature current and field current is known as the V curve. If this procedure is repeated for various increased loads, a family of curves is obtained. The V curves of a synchronous motor are shown below: The point at which the unity power factor occurs is at the point where the armature current is minimum.
How is the power factor of a synchronous motor controlled?
Since the shape of these curves is similar to the letter “V”, thus they are called V curve of synchronous motor. The power factor of the synchronous motor can be controlled by varying the field current I f. As we know that the armature current I a changes with the change in the field current I f.
How does the V curve affect the armature?
From the V curve, we can observe that armature current is changed due to change in field current. When field current is increased from smaller value (keeping load constant), then armature current decreases and at a point it becomes minimum.
What do the points on the V curve mean?
The loci of constant power factor points on the V curves are called Compounding Curves. It shows the manner in which the field current should be varied in order to maintain constant power factor under changing load.