Power Factor of Load Commutated Inverters vs Line commutated Inverters

Thread Starter


Joined Jan 27, 2020
Hi All,

I am aware and familiar with the need to commutate a load commutated inverter's thyristors the load power factor must be leading to ensure that commutation is complete prior to loss of commutation voltage. The power factor is given by Cos(firing angle) which for an inverter is between 90 and 180 degrees and hence gives a negative value = leading.

It would therefore make sense to me that a line commutated converter acting in the inverter region would be the same and provide a leading current. This however to my surprise doesnt seem to be the case, most literature i have read suggests that a line commutated inverter will operate at lagging power factors. In my understanding the converter 'sees' the back EMF of a synchrnous motor the same as it does any grid and hence i do not see the difference. Can someone please explain to me why line commutated inverters consume not generate reactive power?

Eg of a reference that states that it is lagging (although the image looks like its leading) http://www.iitk.ac.in/npsc/Papers/NPSC2002/147.pdf

Thanks for any help - this has really been bugging me as i thought i understood this topic well.