Power factor controller equipment 4

[MAZ13]

I have some questions about capacitor banks and their related equipment. It would be pleasured if you let me know about your experiences.

1)There are some types of power factor controller(regulator) manufactured by companies like EPCOS, Janitza, etc. Do you have any experience in working with these brands? Which one is more simple and easy to use?!

2)Thyristor switched capacitor banks are used to improve power factor in fast variable loads. However, I think that fixed capacitor banks can improve the power factor in this kind of loads, but with low technical characteristic compared to TSCs. I would like to know if there is any other significant advantage in using TSCs considering their high costs?!

 

[rbulsara]

1. Have experience on PFCC systems for industrial/ commercial application but not of those particular makes. You may be in a different country/continent than I am.

2. It all depends on your application and purpose. What are you looking to do and what system/voltage level. I must say I do not have much experience with TSC.

Rafiq Bulsara

http://www.srengineersct.com

 

[Miguel Villarroel]

I suggest you to use fixed capacitors banks bonded to start system in large motors loads, it could be one per big motor too, and to use automatic compensation to help with others loads. About brand all are the same for me ...
If you use local fixed at large motor each feeder will work better, you know

If there was no electricity there would be no internet. Good point, don´t you?

 

[mastergate]

As a general rule:
If ST (kVA) transformer nominal power
and Qc (kvar) capacitor bank power (required compensation)


- Fixed capacitors banks are used if : Qc/St < or = 15%
This is usually used for constant continuous loads, off-load transformer compensation, motor indivudual compensation...


- Automatic regulation is used when Qc/St > 15%.
This is usually used for variable loads, large MCC compensation...

- TSCs are used for fast variable loads compensation (arc furnace, arc welding...).

If you do not have this type of loads, no need for TSCs, you can use either fixed or automatic (normal) compensation.

One important point, you may need to check your harmonics ratio, before to specify type of capacitor banks.

BEN.

 

[waross]

Power Factor Correction may occasionally be used to increase the kW capacity of a feeder but the overwhelming majority of correction is done to avoid PF penalties.
The first step in designing a PF correction scheme may be to check the utility tariffs to determine the basis for the calculation of penalties.
In some countries all KVARHrs leading or lagging, are billed. You need a good controller with a lot of steps to avoid penalties.
With some utilities the power factor is calculated from the monthly KWHrs and the Net KVARHrs. This may often be corrected by one fixed capacitor bank accumulating KVARHrs 24-7.
Other utilities use a similar scheme but include a ratchet on the KVARHr meter so that you cannot accumulate KVARHrs by correcting past unity.
Bottom line, check with the utility before proceeding.

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

 

[MAZ13]

Thank you all for your valuable replies.

In my experience, TSCs installed on a steel plant were able to reduce peak demand current from 3000A to 2500A and it was the major benefit of TSC according to client's opinion. By a fixed capacitor bank it would not been happend.
However, I had not designed TSC for current peak reduction and I believe that if I had considered this purpose, I would be able to reduce peak current even more. I

I am looking forward to get others kindly responses.

 

[waross]

In my experience, TSCs installed on a steel plant were able to reduce peak demand current from 3000A to 2500A and it was the major benefit of TSC according to client's opinion. By a fixed capacitor bank it would not been happend.

An interesting anecdote and I like anecdotes, but there is not nearly enough information to comment on this case.

There are many ways of installing capacitors without using a Fixed Capacitor Bank or a Power Factor Controller. I have had very good results with distributed capacitor installations.

On small installations the cost ratio between a Power Factor Controller and a Fixed Capacitor Bank may be dramatic.

Another anecdote. A very small service with a persistent annoying PF penalty. So small that many utilities would not monitor KVARHrs on a service of this size.
The owner received two quotes for supply and installation of a PFC and capacitors. One quote was double the other quote.
I installed a fixed capacitor and there were no more PF penalties.
The cost ratio between a fixed bank and a PFC installation.- 25:1 and 50:1 respectively.


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