raviiisc

 Profile Answers by raviiisc 

• Apr 9th, 2011

 

The "reactive power" is mainly related with flux in the machine.

The generator generates reactive power if the flux is more than the rated one.

The reactive power flow will be from high voltage terminal to low voltage terminal irrespective of real power flow direction.

The generator reactive power mainly depends on excitation.

bittu123

 Profile Answers by bittu123 Questions by bittu123

• Nov 9th, 2011

 

If alternator is Overexcited, it will deliver reactive power with lagging current
while in Underexcited, it absorb reactive power with leading curreent

But, it always(under or over-excited) deliver real power.

WHY it needs or absorb reactive power??????????
Actually synchronous machine maintains constant flux. when dc field current gets reduced(undrexcited), To strengthen main field, it absorb reactive power(draw current from ac supply mains).
In reverse, when dc field current gets increased(overexcited), To weaken main field, it deliver reactive power to the bus bar.
All these are controlled by magnetising and demagnetising effect of armature reaction

kanchan patkar

• Aug 30th, 2015

 

No, this answer is not sufficient please explain effect of excitation on reactive power

guest

• Jan 10th, 2016

 

Reactive power is energy where the voltage and current are out of phase. It is a produced anytime there is inductance or capacitance in a circuit. By over exciting a generator you compensate for inductance elsewhere in the system, and the voltage and current will in phase with each other.

pradeep1987

 Profile Answers by pradeep1987 

• Feb 4th, 2016

 

It denotes the apparent power by VA/kVA/MVA. The active power is thus VIcos(phi) and reactive power is VIsin(phi). So the reactive power is nothing but apparent power sin component. The machine automatically generates the reactive power.

If the power factor is leading or lagging there must be active power as well as reactive power. Reactive power is necessary for the magnetize the circuit of machines at the generation as well as consumers side, but large amount of this power is undesirable. We need more and more active power so the any machine gives the highest performance at unity power factor with upf the reactive power is zero.

Amit kalyan

• Mar 5th, 2017

 

If there is excessive reactive reverse power the turbine trips.

Riti Biam

• Jun 9th, 2017

 

While generating reactive power can I say that a generator behaves as a motor?

chandana

• Jul 20th, 2017

 

Is it possible to measure reactive power in the generator?

Aruldoss

• Aug 21st, 2018

 

When we have to run the machine at overexcitation..? Means when the reactive power demand will be more at grid end..??

Scott Munnings

• Sep 17th, 2018

 

No. Reactive power flows from high voltage terminals to low voltage terminals regardless of the direction of real power flow. It is controlled by the electrical machines terminal voltage. Motoring describes a real power flow phenomenon. It is controlled by the power transmitted via the shaft of the machine. The difference between generating and motoring is based on the direction of real power flow. When the flow of real power is from the prime mover, through the rotating electrical machine into the system, the electrical machine is acting as a generator. When the flow of real power is from the system, through the rotating electrical machine to the mechanical load, the electrical machine is acting as a motor.
For an AC generator, the prime mover is trying to speed up the generator. The generator is synchronized with the system and resists the acceleration. Power flows from the prime mover to the system. If a control or fuel issue causes the prime mover to try to slow down, the generator is still synchronized with the system and tries to pull the prime mover along with it. Power flows from the system to the prime mover.

Scott Munnings

• Sep 17th, 2018

 

Yes. It is measured for both metering (billing) and protective relaying purposes.

Scott Munnings

• Sep 17th, 2018

 

A machine is run overexcited when VARs are needed by the house load or the grid. Running overexcited up to the machines rating is not necessarily a bad thing. VARs needed to magnetize other machines and transformers have to come from somewhere. That said, the more reactive power (VARs) a machine is producing, the less real power (Watts) it can produce while staying within its apparent power (VA) rating. Recall the power triangle, apparent power is the hypotenuse, real and apparent power are the legs so the pythagorean theorem holds: (VA)^2=(W)^2+(VAR)^2.