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Impact of Local PF at Metering end


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#1 Guest__*

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Posted 19 January 2005 - 04:51 AM

Hi,
If the power factor of supply is held constant at 0.99. The load is 20 MVA. Energy saving device is installed at an Induction Motor for Injection Molding taking average 90KVAh and average pf 0.50 at local end. It is reduced to average 81.2KVAh and average pf 0.56 after installing energy saving equipment. What would be the impact on KVAh Metering End?

#2 marke

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Posted 19 January 2005 - 05:51 PM

Hello

If you have correction to 0.99, then you have virtually eliminated all reactive current from you supply and metering.

If you add a solid state energy saving device to an unloaded motor (I assume a Nola type controller), you wil reduce the voltage applied to that motor and thereby reduce the magnetising current and iron loss in that motor. This will have the effect of reducing the reactive curent for that motor and thereby the correction required. The main correction bank should be reduced to maintain the same level of correction. There will be no change in the KVAh recorded, but there may be a small drop in KWHr. If you had no correction at the main supply, you would see a drop in the KVAHr as well.
The energy saving device, assuming that it is a Nola type, will introduce harmonic currents in the supply which could increase the harmonic current in the power factor correction capacitors etc.

Best regards,




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