I am in the process of validation of APFC controllers for a power factor correction system and bit new to the subject also.I am going thru' some of the controller like ENTES RG-12B series / Mikro's PFR & Novar.After studying product catalog , i have few topics to have a discussion / query.
1. I have seen setting of target cos phi is up to 0.8 LEAD besides 0.8 lag.
When & why that Target cos phi : "Lead" would be required ?generally we know that when
cos phi is required to improve to cos phi :1.00 from say 0.8 lag..then when will be the case where it is required to improve up to 0.8 lead ( e.g )
2. The Capacitor switching is done basically by 3 methods what i found out
a. Rotational / Circular switching
b. Linear switching
c. Intelligent switching.
Rotational switching is that equal steps ( as per cap power ratio setting ) would be switched in /out circular fashion such way that first IN capacitor will be the first capacitor OUT when req. to be disconnected.
Linear switching : In this the Last capacitor IN would be the first capacitor that will be switch OUT when req...... NOVAR 300 follows this linear mode. ( First in Last Out principle)
But in ENTES , they say that in linear mode ....the first or oldest capacitor IN will be the first capacitor req. to be switch OFF or OUT...here it is First IN First OUT.
Hope this switching scheme is standard one ..then why it's different in 1 case.
In Intelligent switching ,i believe it doesn't switch based on any sequence.It sees the req. KVAr and appropriate Capacitors which can supply the req. kVAr.And then switches those.
3. Is it that the controller starts switching when ever
Kvar req = Present reactive power - (Px tan (Arcos(target Cos phi)) is
greater then the present kVAr or any %of Capcitor also needs to be seen ..How this exactly ?
Looking forward to get some hints...
Thanks & Regards,