Voltage problem

I gave you a GA for an excellent and fully correct answer.

The original poster is among the many people that fail to understand that the problem is usually dynamic and only a dynamic fix will really work. For example, as you pointed out, a correction that is built into each offending unit so that only when it is powered up, does the correcting cap come into play......

I have noticed this complete lack of understanding of these types of problems several times on CR4 and if you try and correct their way of thinking, some people get quite upset!!! So I gave up trying to help such stupid people a long time ago!!

I hope your post brings some light into some really dark minds!!

You are over correcting.720KVAR should be split into various segments and depending upon the requirement a bank of capacitors should be switched on

THE SELECTION OF THE CAPACITORS MAY NOT BE ACCURATE .THATS WHY YOUR VOLTAGE IS UNBALANCED DUE TO HARMONICS CREATED BY THE CPACITOR BANKS WHICH WOULD EVEN BE DANGERIOUS FOR YOUR CAPACITORS ALSO.

SELECTION OF HEAVY INDUSTRIAL CAPACITOR BANK IS NEEDED IN ADDITION TO THE APFC PANEL .I.E AUTOMATIC POWER FACTOR CONTROLER WHICH WILL SENSE THE LOAD AND ACCORDINGLY IT WILL DECIDE HOW MANY CAPACITORS ARE REQUIRED TO OPERATE.

Sorry friends, I forgot to write that this bank is controlled with APFC & also controller is switching ON & OFF the small capacitors automatically as per inductive load.

Hello "Guest",

That is a very important piece of information which you "forgot" to mention earlier.

Are such "memory lapses" often occurring, if so you need to seek urgent help, because you risk damage to equipment, a penalising power account, and possible personal accident to your good self.

Taking this "previously unmentioned fact" into account, there are only two possibilities:

1. The APFC controller is faulty
2. The APFC Controller has been incorrectly set

If the APFC Unit and capacitor Bank are new, then your recourse is:

If (1) above, then contact the supplier immediately.

If (2) above, then get an Electrical Technician or Electrical Engineer, who has the Test Equipment available, and knows how to use it, to set the APFC setting correctly.

Let us hope you have had no further "memory lapses", because electricity needs a clear head, proper knowledge, correct Test Equipment, no memory lapses, and other necessary items for your being able to run equipment such as an APFC unit properly, automatically and safely.

Kind Regards....

Did you measure the power factor for the 3 phases on which you try to compensate the inductive power ?

Based on the resulting power factor you can determinate if you overcompensate or not and go on from there.

May be capacitor in one of phases in one or more of units being open or faulty.

hi

the capacitor bank of 720 kvar is of fixed rating, u can't adjust the kvar supplied by the bank,

the rating is based on some kw load and PF keeping in mind, at the time of kvar calculation,

this bank will raise the system voltage if the load is less then calculated one, so at less or reduced load the capacitor bank's kvar also needs to be adjusted accordingly,

if u don't adjust the kvar of bank, the kvar supplied by the bank will increase the system voltage by10 to 20 % approx.

u need to make variable bank means u can adjust the kvar of the bank when u needed

best regards

divyesh patel

I don't agree the last part of your post.

"...but I don't believe a PFC can increase voltage, only return its value to the same as supply, otherwise everyone would use it to "Create Free Energy"

Increasing voltage level is not the same as increasing mean energy.

You are thinking of the CAPS of PFC alone. This is not the case, think of them with the inductances on the network.

These caps and inductances resonates and this phenomenon is encountered as increase at voltage level if the load current is below than that of PFC designed. Means these are transient peaks actually and decay factor depends on load current.

Regards

Dear Sir,

Pl check actual requirement of capacitor ( 720 seems high) and put it.

My expectation is you have put heigher capacity.

Dear Sir,

Your problem does not lies with the Capacitor Bank. You donot have any voltage problem. Normally a capcitor bank injects leading (VAr) Power factor. If your turn on the Capacitor then The Voltage rises.

if you really want the capcitor bank to run, then lower the tap of the Power Transformer.

Regards,

N.Suresh

N.Suresh, you are probably correct. While it is possible that the bank is over-compensating, it is not the only possibility. Measure the power factor with the capacitor bank on. If it is below 0.98 lagging, you are OK. Simply reduced the transformers taps. They were originally set high to compensate for the voltage loss in the cables at low power factor.

Hello friend,

Basically capacitor bank is used to increase the voltage in order to improve power factor.In your case , already you have normal voltage means don't add capacitor.This case you should check the plant running electrical equipment and find out which one is running with 70 or less than 70 % of the load and change that existing electrical motor with less capacity to met 90 and above % your power factor will improve by it.

so ,its clear my friend u should go for less kvar capactior bank or increase ur load correspondingly

Hello,

Your capicitor bank is over correcting your power factor beyond 100%

That puts you in a lead position. You need to throttle your bank by adding a controller that automatically corrects by connecting or disconnecting capacitors within your bank to get you close to 90% power factor. Your local power company rep will tell you what level they want you at.

Hope this helps

From the replies I've read so far, Sapper seems to be the closest to the actual problem. One of the side effects of PFC is the noticed lack of voltage drop that was previously on the system. The lagging current is now being offset/supplied by the PFC, so the voltage drop it imposed on the system will no longer be present, giving the illusion that the caps are increasing the voltage.

Leave the caps on-line, readjust the taps on your in-coming transformer(s) to the desired voltage, and then pat yourself on the back for all the cash you will not be paying the utility.

We had a similar problem testing so AC power. Our final conclusion was that the power was looping thus incressing.

As a result we are now and have been working with DC power only and later converting it to AC.

In short. Much greater control. Plus larger amounts of DC can be stored for use as needed and with AC thats not the case for much long term use.

Thank You,

Sarah Angelina DeLagostti
www.DeLagostti-Industries.com
Manhattan, New York City
United State Territories

Are you joking?

Hai,

do you have harmonic generating equipments installed recently e.g Motor drives ,smps units etc.

you may be developing a resonant circuit loop thus developing a higher than normal voltage .

switch off the above mentioned equipments and observe.

Also check the Neutral to ground voltage ,you may be having a floating neutral .