power factor issue

[zoo123]

power factor issue at my shed , seek advice?

dear friends, i have a commercial power line taken from Govt owned lines, as is usual.

with my new start up, i registered for a min. use of 4kw and connections provided in 2021. I changed the same to permanent conneciton in end of 2023.
Since, then i have been using one welding machine mobile carry type and one hand grinder for weld work related fabrications. The wattage of weld machines never exceeds 2 KW,
and the hand grinding machine 0.5KW.

RECENTLY I WAS levied a heavy penalty for a very low power factor of 0.2. But, when i see the digital meter it shows 0.07 or around that.

I also, use a Capacitor bank unknowing on the conneciton method. but they keep charging me once again.

Now, upon, raising the query, the capacitor bank trader says for 4 to 6kw , this is an issue for low power and it can never be solved.

The govt department adviced me not to keep the capacitor nearr the mains, but shift it to my welding machine and switch it off and swith on during the usage only.

i am perplexed and unhappy that my start up is being robbed for no reason of mine. can i know what i must do to increas the pf and avoid the fines. please advice me.

thank you all.

 

[electricuwe]

From your description of load there is no reason to use a capacitor bank.

Your (small) welder most probably uses power electronics may even provide power factor correction and the grinder has low power and might rune in worst case at a power factor of 0.6 or 0.7.

 

[zoo123]

From your description of load there is no reason to use a capacitor bank.

Your (small) welder most probably uses power electronics may even provide power factor correction and the grinder has low power and might rune in worst case at a power factor of 0.6 or 0.7.

thanks for your inputs. but at the end of the day, the Govt people keep penalising my small start up intentions and heavy penalty levied on me. The power factor of 0.1 , means i utilise a current on a average of 5 to 8 amps, but with the VAR, iT SEEMS they pump in 150 amps. so, how i effectivly change the poor PF of 0.07 or 0.1 to 0.8 ,

 

[crshears]

Hmm, have I not seen threads in these fora relating to commercially available small scale power factor correction units for use at Point Of Common Coupling [ POCC ] ? You might want to do a search . . .

 

[zoo123]

meanwhile not sure what u meant by POCC. aLSO, It would be good to know if the capacitor can be kept on always or how it has to be connected. can you throw some lights. thanks though

 

[waross]

First, you don't supply enough information for an accurate assessment.
There are so many ways that various power companies calculate power factor for the purpose of penalties that just giving us the utility PF is not very helpful.

But here is an example that mat apply in your case;
Load: 1 kW, 1 KVAR, in use 0.5 Hr. per day.
VARHr used = 500 VAR Hr per day.
PF 50% lagging.

Correction of 1 KVAR switched with the load = 100% PF.

Correction of 1 KVAR on the mains = 23 KVARHr per day
(23.5 KVARHr leadinf minus 0.5 KVARHr lagging = 23 KVAR leading) leading current with a power factor of 2.17%

Either correct your welder to 100% with caps switched with your welder or hire an expert familiar with local tariffs.

 

[crshears]

Hello zoo, waross is correct; I agree more with his second recommendation, viz., you should find a local expert in power factor penalties.

My reference was to a power factor correction unit that connects at the point of common coupling, meaning where your electrical services and your power company interface. Such units measure the power factor of your site on an ongoing basis, and use controlled capacitors and/or reactors to adjust your site power factor to very close to unity [ 1.0 ] in real time; that way your utility will never find you with a poor factor, whether it be lagging [inductive] or leading [capacitive], and can therefore never assess such a penalty against you.

This can be very expensive to implement, though, hence the strong recommendation to find a knowledgeable power factor penalty expert for your area to assist you so you will not spend money unnecessarily.

 

[electricuwe]

You have to be aware that poor power factor can be caused by inductive load (lagging) or by capacitive load (leading). Unless you know your power factor without any capacitors connected you can`t decide.

Maybe you just pay the penalty for the capacitorys causing leading power factor.

 

[zoo123]

Dear friends, my sincere thanks to you all for the reply and input advices you provide. thank you.

I want to indicate to you that the Govt utility( power company) people, inspect and specifically look for a capacitor bank avaialbility prior to approving the connection.

While, that said, how to connect caps. where to connect caps. etc, was not specific. intially, they adviced and per their inputs for a 4kw load, i connected 4kvar caps kIT in the supply. output end of meter.

Having said, that the caps, i left it always connected despite work or no work. may be my poor understanding.
The Caps failed in an year and upon trying to replace them, the warranty period was over and I replaced the same upon getting a penality.

Despite a second time penality, i had to raise SOS to the utility guys and they asked me to switch on and off the caps. while using the weld and grind machines.

I am not sure leaving the caps, on 24x7 had caused this issue or not connecting the caps, near the weld input is causing the issue. When i use a current of 5amps, regular the kvah is equivalent to 150amps. regular that causes my PF to 0.07 or 0.1.

 

[edison123]

govt department advised correctly. 24x7 capacitor with no other inductive load will drop your pf like a stone.

 

[bacon4life]

There are many ways for utilities to implement power factor penalties. Can you share exactly which utility you receive power from? In my region, small loads like this would not be subject to power factor penalties.

 

[Gr8blu]

The value of the correction is dependent on load. If your caps are on (with welder and/or grinder operating), the utility sees a "corrected" power factor close to unity (but still lagging). If the caps are disconnected and the machines are operating, the utility sees the actual lagging power factor of the machines - which will vary from 0.20 to 0.70 per unit. If the caps are left connected and the machines are offline, the utility sees the leading power factor of the caps - which may be VERY low (0.05 to 0.030 per unit).

Best way to optimize power factor correction is dependent on MINIMUM load at the utility connection. If there will always be some load, connect the necessary PF correction required FOR THAT LOAD at the utility point, and leave it always connected. If other loads are on/off usage, connect the proper PF correction at the machine and have it switch on/off with the machine.

In your case, it looks like the load varies from zero (nothing operating) to max (welder and grinder, with maybe lights and a few other devices). Proper way to correct PF would be at each major load. Correction should be to bring observed PF at that point (for example, at the welder's terminal box) up to around 0.95 lag or so, to ensure everything else works properly.