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If the load on an AC system is purely resistive, then the voltage and current waveforms will be in phase. A desirable state.
When the load has some reactance, then these two parts of the power signal will not be in phase; and this results in an inferior power generation, in which some of the work needed to generate the signal is not available as real work at the terminus. This undesirable condition occurs with both inductive loads such as electric motors, and capacitive loads, such as fluorescent lighting.
This may be corrected for in real-life systems by employing 'power factor' correcting equipment. One common device is the 'rotary capacitor' - in reality, a rotating transformer in which the phase is controlled as to make it appear as a capacitor, not as an inductor.
Ordinary Transformers transfer the reactance of their load, with a small percentage of genuine reactance due to hysteresis losses in the core of the transformer.
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What does capacitive reactance oppose?
Inductive reactance.
What is difference between resistance and reactance while both are measured in ohms?
Resistance is constant no matter the frequency applied. Reactance varies depending on the frequency of the power applied to it.
What is the symbol for inductive reactance?
Inductive reactance does NOT have it own sign or symbol. Rather, it uses Ohms as a quantifier. But Capacitive reactance ALSO uses Ohms as a quantifier. Fortunately, 1 Ohm of Inductive reactance is cancelled by 1 Ohm of Capacitive reactance at the same frequency of measurement.
What load impedance Z will result in maximum power transfer from an electric source with an internal impedance of r?
For maximum power transfer, source resistance should match load resistance and source reactance should match load reactance with the opposite sign (so if the load is capacitive, the source should be inductive).
What is the use of reactance relay?
reactance relay is used for distance protection of the transmission line....
How is the power factor improved in an AC system?
by adding the opposite type of reactance. as motors are a common industrial load and their reactance is inductive, add capacitive reactance.
Is reactance major responsible for power loss in power transmission lines?
Reactance certainly causes loss in a transmission system, but I^2R or resistance losses are greater.
In electrical power transmission the line must have reactance to flow of the power without the reactance the power cannot flow please answer for this if required give mathematical expression thanx?
Electrical transmission lines do have reactance, but it is not necessary for power to flow. In fact, the smaller the reactance, the higher the efficiency of the transmission system. Reactive power is not delivered to the load, it does no useful work, it just costs money to generate and causes heating of the conductors.
Does the power factor in three phase system depend on the phase sequence?
No. It depends on the inductive and capacitive reactance of the load.
What are the three types of opposition to current flow that impedance represents?
There is pure resistance, inductive reactance, and capacitive reactance.
What is percentage reactance?
Percentage reactance of a transformer (or in general, a circuit) is the percentage of phase voltage drop when full load current flows through it, i.e %X=(IX/V)*100. Now Short Circuit Current is V/X So short Circuit current is I*(100/%X).
Why load angle is positive for generator and negative for motor?
simply put a motor consumes power and a generator produces it. reactance of a generator = - reactance of a motor
What is percentage reactance of trasformer?
Percentage reactance of a transformer (or in general, a circuit) is the percentage of phase voltage drop when full load current flows through it, i.e %X=(IX/V)*100. Now Short Circuit Current is V/X So short Circuit current is I*(100/%X).
What is the physical meaning of power angle in a power system?
a curve drawn for power against load angle maximum power occurs at load angle of 900 maximum power will be transffered from sending end to receiving end when the reactance is 1.732 times its reactance
Why the value of power factor should be low?
no.... the power factor of any machine should be as near as to 1 when the power factor becomes near to 1 there is no need to the alternator to supply the reactive power.. but in general all most all the loads in the power system inductive in nature the power factor is becoming lagging(<1) so to avoid this the power generating companies and the govt. are recommending the people to have the capacitors at the load ends....... since the capacitive reactance can nullify the effect of the inductive reactance this will try to improve the power factor
What is the power dissipated by a reactive load?
No power is dissipated by a load composed exclusively of either capacitive or inductive reactance.
What is the usual value of the reactance to resistance ratio in power distribution lines?
0.1~10
