Table of Contents
- 1 What happens if one of the alternators of which excitation is changed?
- 2 What is the effect of change in excitation on the power factor of the synchronous motor?
- 3 What are the effects of excitation on alternator EMF?
- 4 What is the effect of excitation?
- 5 What controls the excitation voltage and modifies the excitation?
- 6 What two factors affect the frequency of an alternator?
- 7 How does change in excitation affects alternators connected to infinite bus?
What happens if one of the alternators of which excitation is changed?
If the excitation is changed, it will change the field magnetism created inside the alternator and the voltage generated in the stator winding is likely to be affected.
What is the effect of change in excitation on the power factor of the synchronous motor?
As the excitation is increased, the power factor improves till it becomes unity at normal excitation. Under such conditions, the current drawn from the supply is minimum. If the excitation is further increased (i.e., over excitation), the motor power factor becomes leading.
What happens to the power factor of an alternator operating in parallel with other alternators if its excitation is increased above the normal value of excitation?
If the excitation of an alternator operating in parallel with other alternators is increased above its normal value of excitation, its power factor changes in the lagging direction and its current output increases with no appreciable change in its kW load.
What are the effects of excitation on alternator EMF?
If their excitations are the same, they induce the same emf, and since they are in parallel their terminal voltages are also the same. When delivering a total load of I amperes at a power-factor of cos Ф, each alternator delivers half the total current and I1 = I2 = I/2.
What is the effect of excitation?
A change in the excitation of an alternator running in parallel with other affects only its KVA output; it does not affect the KW output. A change in the excitation, thus, affects only the power factor of its output.
How does excitation effect power factor?
When the field excitation (Ef) of the motor is changed, the armature current (Ia) changes. But the product (Iacosφ) must remain constant. For this to happen, the power factor angle (φ) adjusts itself in such a way that product (Iacosφ) remains constant. That is, the power factor of the motor will change.
What controls the excitation voltage and modifies the excitation?
The DC excitation system has two exciters – the main exciter and a pilot exciter. The exciter output is adjusted by an automatic voltage regulator (AVR) for controlling the output terminal voltage of the alternator.
What two factors affect the frequency of an alternator?
Two factors affect the frequency in an alternator: rotation speed and the number of poles.
Why excitation is required for alternator?
The excitation system is responsible for supplying the field current to the main rotor. The requirements of an excitation system include reliability under all conditions of service, a simplicity of control, ease of maintenance, stability and fast transient response.
How does change in excitation affects alternators connected to infinite bus?
When the excitation of an alternator connected to infinite bus-bars and supplying load at lagging of is increased, the alternator falls back (i.e., load angle decreases), power factor further drops and armature current increases due to reduced power factor; active component being constant.