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How does the variation of excitation of an alternator correct power factor?
Wiki User
∙ 15y ago
The rotor of an alternator need a DC voltage applied to it to generate a magnetic field, this magnetic field will generate the AC power in the AC windings.The AVR(Automatic Voltage Regulator) is regulating this DC voltage so that the magnetic field is strong enough to maintain the output AC voltage. As soon as more current is drawn from the output, this output voltage will drop and a stronger magnetic field is needed to sustain the output voltage, so the AVR step up the exiting voltage to get a stronger magnetic field to compensate for the voltage loss in the AC windings.
Wiki User
∙ 15y ago
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How can the variation of excitation of an alternator be used to control power factor?
When a generator is connected to a load it is never going to be perfectly matched because of its inductance, when you have inductance the current starts to lag.
Why the rotor of an alternator at rated power dissipates more heat at a low power factor load?
In an alternator, the load current is supplied by the stator and the excitation is applied to the rotor. When the power factor is low (lagging), more excitation is required to maintain rated output voltage at rated current. More excitation is also required to maintain rated output voltage with increased output current. Increased excitation current means increased rotor losses that must be dissipated as heat. (akash)
Can we improve generator power factor for increasing active power?
The 0.8 Power Factor provided by generator manufacturers is not the load power factor, but it is the nominal power factor used to calculate the kW output of an engine to supply the power for a particular alternator kVA output. Alternators are therefore designed to supply their rated kVA at 0.8 lagging power factor.
What are the disadvantages of leading power factor on generator supply system?
in case of leading power factor the air gap flux inside the alternator will increase which may cause over heating of the stator end coil and overhang portions.
What are the factors affecting the stability of a Q-point?
(1) current amplification factor due to change in temperature. (2) collector current because of variation in leakage current.
How can the variation of excitation of an alternator be used to control power factor?
When a generator is connected to a load it is never going to be perfectly matched because of its inductance, when you have inductance the current starts to lag.
Why the rotor of an alternator at rated power dissipates more heat at a low power factor load?
In an alternator, the load current is supplied by the stator and the excitation is applied to the rotor. When the power factor is low (lagging), more excitation is required to maintain rated output voltage at rated current. More excitation is also required to maintain rated output voltage with increased output current. Increased excitation current means increased rotor losses that must be dissipated as heat. (akash)
What affect does a leading power factor have on alternator generator excitation currents?
When a leading power factor load is applied, the voltage of the genset or genset bus rises, and the voltage regulation system reduces exciter power, reducing the strength of the magnetic field. If the field fails, the generator set may slip a pole, which results in potentially catastrophic alternator damage. pawan
When you should use synchronous motor instead of capacitor for power factor correction?
Synchronous motors show some interesting properties, which finds applications in power factor correction. The synchronous motor can be run at lagging, unity or leading power factor. The control is with the field excitation, as described below:When the field excitation voltage is decreased, the motor runs in lagging power factor. The power factor by which the motor lags varies directly with the drop in excitation voltage. This condition is called under-excitation.When the field excitation voltage is made equal to the rated voltage, the motor runs at unity power factor.When the field excitation voltage is increased above the rated voltage, the motor runs at leading power factor. And the power factor by which the motor leads varies directly with the increase in field excitation voltage. This condition is called over-excitation.The most basic property of sycho motor is that it can be use as a CAPACITOR OR INDUCTOR both. Hence in turn it improves the power factor of system.The leading power factor operation of synchronous motor finds application in power factor correction. Normally, all the loads connected to the power supply grid run in lagging power factor, which increases reactive power consumption in the grid, thus contributing to additional losses. In such cases, a synchronous motor with no load is connected to the grid and is run over-excited, so that the leading power factor created by synchronous motor compensates the existing lagging power factor in the grid and the overall power factor is brought close to 1 (unity power factor). If unity power factor is maintained in a grid, reactive power losses diminish to zero, increasing the efficiency of the grid. This operation of synchronous motor in over-excited mode to correct the power factor is sometimes called as Synchronous_condenser.
What does a stator do on an alternator?
The stator on an alternator is used to generate a magnetic field. This is a large factor in the production of electricity.
What is the number one factor that determines variation in climate?
latitude
When two alternator running in parallel the power factor from 8 drops to 5 or less why is it so?
power factor 0.8 drops to .05 when two alternator running in parallel
Is 8 a factor of 40 but not a factor of 100?
That is correct.
What are v and inverted v curves?
V Curve- Excitation vs Armature currentV curve is the graph showing the relation of armature current as a function of field current in synchronous machines. The purpose of the curve is to show the variation in the magnitude of the armature current as the excitation voltage of the machine is varied.Inverted V Curve- Excitation vs Power FactorThe synchronous motor "V Curves" shown above illustrate the effect of excitation (field amps) on the armature (stator) amps and on system power factor. There are separate "V" Curves for No-Load and Full-Load and sometimes the motor manufacturer publishes curves for 25%, 50%, and 75% load. Note that the Armature Amperage and Power Factor "V" Curves are actually inverted "V's".Assume it is desired to determine the field excitation which will produce unity power factor operation at full motor load. Project across from the unity power factor (100%) operating point on the Y-Axis to the peak of the inverted Power Factor "V" Curve (blue line). From this intersection, project down (red line) from the full-load unity power factor (100%) operating point to determine the required field current on the X-Axis.In this example the required DC field current is shown to be just over 10 amps. Note at unity power factor operation the armature (stator) full-load amps is at the minimum value.Increasing the field amps above the value required for unity power factor operation will cause the machine to run with a leading power factor, while field weakening caused the motor power factor to become lagging. When the motor runs either leading or lagging, the armature (stator) amps increases above the unity power factor value.
What is the relation between power factor and frequency for purpose of parallel operation of alternator?
No relation is there power factor is a unit less quantity.
What is Two-way ANOVA (surface)?
In a two-way ANOVA on the surface, the relate in an equation the total variation, , where i=1,2,…,a and j=1,2,…,b; the explained variation by the "treatment" or first factor is , the explained variation by the "block" or second factor is and the unexplained variation . SST= SSA+SSB +SSE Degrees of freedom N-1 a-1 b-1 (a-1)(b-1) N=ab
Does the value of the exciting current of your 3-phase motor depend on the rotor speed?
An induction motor has no excitation, so the question is about a synchronous motor. The rotor speed is determined by the supply frequency. For a given supply frequency and mechanical load, the excitation current can be adjusted to give the best power factor.
