Bulk capacitor and switched capacitor mind 1

[motorrepairman]

Dear All

I am new in this forum and I would like to know how can I make a difference in this two kinds of capacitors (power factor correction speaking) and it term has a Synonimus

Thanks

Motorepairman

 

[bacon4life]

Capacitors for power factor correction can either be fixed or switched. What voltage level are you thinking of?

Some common locations for capacitors include:
120V to 600V Capacitors on individual motors, switched in & out with the motor.
4kV to 35 kV Capacitors near the utility service to correct the power factor for the entire customer site.
4kV to 35 kV Capacitors on utility distribution lines
4kV to 35 kV capacitors at utility distribution substations,
69 kV to 765 kV Capacitors at transmission substations.

Welcome to the site. Please do not cross post between forums because most of us read both forums. You can remove the post in the "Electric motors, generators & controls engineering Forum" by clicking on the red flag icon.

 

[crshears]

...and when he deleted the post in the electric motors, generators & controls engineering forum, he also blew away my response to it...just bad timing, I guess.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[motorrepairman]

Sorry crshears the question has been deleted, bacon4life I am trying to imagine this terms so can you explain how are builded each one of this capacitors? what is the main difference? are ther any synonimus for each one?

Thanks again

 

[motorrepairman]

crhears you can also answer to me with your latest answer in the other forum

 

[bacon4life]

Do you mean synonymous? Most capacitors used on the power system have similar construction, but might get called many different things by different people. Here are some pictures of different voltage levels. Whether or not the capacitor is switched doesn't really have much to do with the capacitor itself. The switching device is a totally separate piece of equipment that is typically mounted adjacent to the capacitor bank.


480V type:

http://www.ebay.com/itm/GE-General-...citor-Cat-37F650G6-480V-3-Phase-/251144952966

Pole mounted distribution capacitor:

http://3.imimg.com/data3/TN/SD/MY-1018626/pole-mounted-capacitor-bank-250x250.jpg

substation capacitor bank:

http://image.shutterstock.com/displ...bank-in-high-voltage-substation-124054798.jpg

 

[crshears]

Hello motorrepairman, as bacon4life has requested please specify the voltage level and application you are asking about; that way answers provided are more likely to give you what you want to know.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[motorrepairman]

Thanks for the answers,

I am not intended to any specific application I am looking only for a definition of each term, "Bulk" capacitor and Switched capacitor in power factor correction in general.

i.e. Bulk capacitor: Capacitor connected a distribution board and controlled independiently. It´s correct?

i.e. Switched capacitor: Capacitor that can be switched in or out of the circuit to apply the desired degree of capacitor to achieve the required correction. It´s correct?

Thanks

motorrepairman

 

[crshears]

So it's a terminology question; not sure how to answer...

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[waross]

When capacitors are to be added to an industrial plant to correct the power factor you may chose between bulk correctin and switched correction.
Historically the power factor of a plant was calculated on a monthly average and penalties applied when the monthly average dropped below 90%. The active power, KiloWattHours, and the reactive power, KiloVoltAmpReactiveHours, from the revenue meter were used to determine average monthly power factor. The monthly average could be corrected by connecting bulk capacitors and adding a set amount of KVARs or KVARHrs per month. At times of low load the power factor may be leading, and the voltage may rise enough to damage lighting. At times of heavy loading the power factor may be low, but at the end of the month the average would be high enough to avoid penalties.
A compromise was to connect as much bulk capacity to the sevice as was possible without incurring over voltage issues and then to connect capacitors to large motors so that the capacitors were switched with the motors. On the assumption that when the large motors were running there would also be a number of smaller motors running, the large motors may be over corrected. Typically the amount of capacity required to correct a motor to unity would be doubled.
A typical saw mill in the Pacific North West may run 16 Hrs per day for 5 days per week. The lumber kilns often ran 24/7.
Comparing 16 Hrs. x 5 days = 80 hours per week, with 24 Hrs x 7 Days = 168 Hrs per week it as apparent that capacitors switched with the lumber kiln fans would be twice as effective in correcting the monthly average.
Even though some capacitors may be switched with motors, this may still be classified as a bulk correction scheme.
That was then and this is now.
Metering technology has progressed and the electronic meters are able to meter any use of KVARHrs. Some utilities are able to and do penalize any and all use of KVARHrs outside of allowable limits. That is low power factor.
Switched capacitors in an industrial plant may now include a Power Factor Controller.
The PF controller monitors the power factor in real time and switches capacitors in and out so as to maintain the Power Factor of the plant at or near unity.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[motorrepairman]

Thanks Waross

So taking account your explanation a Bulk correction is a central correction that can be made it with fixed capacitors or capacitors switched manually or automatic and the switched capacitors are this ones that are permanently connected to one large motor but only works till the motor is powered?

Thanks again

motorrepairmen

 

[waross]

No A bulk correction scheme may include capacitors switched with a large motor.
Bulk is mainly to correct the monthly average power factor.
Switched uses control to maintain the power factor at a set operating point or range.
There may be other definitions.
You may think of bulk correction as the art of power factor correction and switched as the science of power factor correction.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[motorrepairman]

Great Bill now is clear

Thanks a lot.

motorrepairman