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capacitor in every machine


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#1 Guest__*

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Posted 23 October 2005 - 08:03 AM

Dear Sir,
I want to know about energy saving from capacitor.
one of my friend have just install capacitor in his factory.
He install each of his machine panel a capacitor. beside it he has a capacitor bank in his factory.
he said that capacitor bank is working only for power electrical supplier's penalty cause of poor power factor. but it didn't work for power efficiency.
When he install the capacitor in every machine panel, his electrical bill is decreased very much. so that he can get payback period for 3 months.
He need about US$10000 to install this capacitor.
My question is : it is true what he says that with capacitor in every machine we can get efficiency so we get lower bill?
If it is true, how to determine the capacitor size for every machine, since every machine has different motor?
Is this system work for heater or only for motor?
For additional information is that his factory is plastic machine for injection molding.
thank you for your answer.

#2 marke

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Posted 23 October 2005 - 06:57 PM

Hello

If you register on the forum (free), you can get email notifcation of replies.

Power factor correction will reduce I2R loses in cables. The losses should not be significant within a plant, so there should not be any significant savings from fitting the individual capacitors. If the savings are significant, you will achieve higher savings by increasing the cable sizes!!

The addition of capacitors will not affect the efficiency of the motors or machines, only reduce the line and cable losses where there is a poor power factor.

Best regards,

#3 Guest__*

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Posted 27 October 2005 - 07:00 PM

Thank you for your answer;f;
you said that to get significant saving by increasing the cable. which one do you think the cheaper one. By invest in cable or I must add the capacitor like my friend did.?

I have try to register but it seem failed. i will try again.

#4 Cahya

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Posted 27 October 2005 - 07:04 PM

Hello. Now I have register. my name is Cahya.

#5 marke

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Posted 27 October 2005 - 07:20 PM

HI

The question is whether you have significant losses in the cables.
If you do, then thos losses can be reduced by reducing the current, and this can be achieved by adding power factor correction where motors have a poor power factor, or by increasing the cable size. If the cable losses are low, adding power factor correction will not acheive much for your cable losses bu may assist in reducing any KVA max demand or pf penalty that you pay.
For example, if you have a cable run to a motor that has a 10% voltage drop, you will have a 10% KW loss. If you run a second cable, the same size in parallel with the original, you will halve the loss to 5%. If you run a larger cable such that you have only say 2% voltage drop, you will reduce the losses to 2% - an 8% saving. (80% of cable losses)

If at the end of your cable with 10% loss you have a motor with a power factor of 0.5 and you correct that to 0.9, you will reduce the current flowing in the cable to 55%. This will reduce the losses for a length of cable to .55 x .55 (I2R) or 30% of uncorrected losses. Note this savig only applies for the period when the motor load is reduced. High loading losses are not affected much. Increasing the cable size provides a saving under full load as well as reduced load.

If your cable losses are low, say 2%, then reducing them by say 50% with pf correction on an unloaded machine, will be 50% of 2% which is 1% of the connected load and this is quite small.

Best regards,

#6 marke

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Posted 27 October 2005 - 07:50 PM

Hello Cahya

Further to my previous posts, are you paying a significant penalty for poor power factor, or for KVA max demand? If you are then the power factor improvment will give you a payback.
If you have severe penalties, you can reduce them by adding bulk pf correction at the main board. This may be cheaper than connectin to each motor.
Bulk correction will not address cable losse within your plant though.

Best regards,




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