Power Factor Correction CT
Power Factor Correction CT
(OP)
Hello,
I am having a bit of trouble determining what CT burden I will need for a PFC unit which will be connected to a 415V MCC.
I have read a bit of information on the requirements of standard PFC units and from what I can gather they require a Class 1 metering CT and 15 VA burden with 5A secondary.
My question is - can I connect a CT with a greater burden than 15VA? I can only source a 60VA CT due to the size of the busbar it needs to connect to. My thoughts are that it will be ok and that the PFC unit will only draw what current it needs and a burden greater than 15VA will not damage the PFC unit.
Also 1 more question - I have been told to put the CT on the red phase by several sources (manufactures). Why would they recommend this? Surley it doesnt matter what phase the CT is connected to.
Thanks
I am having a bit of trouble determining what CT burden I will need for a PFC unit which will be connected to a 415V MCC.
I have read a bit of information on the requirements of standard PFC units and from what I can gather they require a Class 1 metering CT and 15 VA burden with 5A secondary.
My question is - can I connect a CT with a greater burden than 15VA? I can only source a 60VA CT due to the size of the busbar it needs to connect to. My thoughts are that it will be ok and that the PFC unit will only draw what current it needs and a burden greater than 15VA will not damage the PFC unit.
Also 1 more question - I have been told to put the CT on the red phase by several sources (manufactures). Why would they recommend this? Surley it doesnt matter what phase the CT is connected to.
Thanks






RE: Power Factor Correction CT
The burden on the CT is determined by the attached cabling and instruments so I can't see that you'd damage the PFC unit
RE: Power Factor Correction CT
In short the answer is yes, you can use a 60VA burden CT.
Lspark-
Not all CTs tend to be less accuracy at low burdens. In general, the accuracy improves at low burdens. However, in the IEC world, CT accuracy only has to be maintained from 25% to 100% of rated burden. Some manufacturers use that to "shift" the load line by using parallel turns correction to reduce the size of the core, thus saving on material cost. In my opinion, the 25% burden range is something that needs to be changed in the IEC standard, given modern device burdens being so low.
RE: Power Factor Correction CT
Bill
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"Why not the best?"
Jimmy Carter
RE: Power Factor Correction CT
However, in the end, it often ends up being a compromise because you can't get a CT with a low enough VA so you can expect it to saturate before providing enough current to damage the controller.
The power factor controller should have a connection diagram in the manual. It won't be capable of properly calculating the power factor if you don't follow the connection diagram.