Reactive Power Relation with Alternator

How reactive power is related to alternator? Wheather it is generated or consumed? Explain

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rajakumar1985

  • Oct 16th, 2009
 

The alternator is always generating the real power along with the reactive power. This will never consume the reactive power. The induction generator only consume the reactive power. The output reactive power of the alternator is decided by the type of load. . .

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GeeK_Percy

  • Oct 18th, 2009
 

If syn m/c is under excited that means it is not able to produce reactive power itself which is required so it will take reactive power i.e. act as induction generator.

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buntysurat

  • Oct 23rd, 2009
 

An Inductive Load say Induction Motor connected to an Alternator requires Active (KW) & Reactive Power (KVAr) both. This Motor receives Apparent Power (KVA --> KW + KVAr) from the Alternator. Active Power is what the Motor is delivering through its shaft and the reactive Power is what it is consuming internally to deliver the rated Output.

So, if Motor Power Factor is 0.8 then, it is said that Motor is coverting 80% of its Input Apparent Power into Mechnical Output consuming remaining 20% Apparent Power internally. So, the motor is demanding 20% reactive power being generated by the alternator.

If the Power Factor of Motor is improved to 0.95 by means of External Capacitor then it should be understood that out of 20% of reactive Power required by the Motor 15% is supplied by external Capacitor and remaining 5% is being supplied by Alternator. so, the Apparent Power Output of the Alternator reduces whereas Active Power Output remains constant as Motor KW. 

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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

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