I am having some issues in one of my projects. We have installed a generator in a building, where power factor is leading and -kvrs are shown on controller display. We know that this building is filled up with LED lights, due to which the genset controller orders a shutdown. We have consulted with a local vendor and he recommends installing a line reactor between genset and load. But even after installing this reactor still there is the same result. If you can help please give some suggestion.

  • 2
    \$\begingroup\$ There are no numbers in your question so I suggest you start there. You need to look up the datasheet for the generator and find what its operating ratings are. You need to measure the kV, kVA and power factor of the load and see how much correction you need. You need to get the specifications of the reactor you installed and see if that was enough. Do your calculations and compare with actual measurements. \$\endgroup\$
    – Transistor
    Commented Sep 12, 2018 at 17:53
  • \$\begingroup\$ Even without the concern of the generator, in most areas the power company may require you to correct it if they notice it. In some cases, especially for large building contracts, going outside a certain total load boundary or having power factor cease to be between .8 and 1 lagging negatively affects the overall network. Building operators sometimes cause this by starting too many inductive loads at once. It's referred to as "blowing demand" among the guys I knew and it was a top tier mistake for them as it subjected their entire monthly bill to a multiplier. \$\endgroup\$
    – K H
    Commented Sep 15, 2018 at 2:44
  • \$\begingroup\$ A large inductor/reactor only corrects for true phase angle problems. With LED lighting a power factor problem may show up as a load phase problem, BUT IT ISN'T !!! It's a conduction angle problem, and no inductance can ever fix it, When powering LED lighting you need to derate the genset to compensate. That's it ! \$\endgroup\$ Commented Oct 10, 2020 at 21:14

1 Answer 1


Non-filament LED bulbs have a bridge rectifier and capacitor in their mains supply. That's usually not a problem as the current spikes that kind of supply creates are small for a few watts LED bulb. It doesn't matter then.

For that reason (and size), the PFC requirements today's mains supplies have to adhere do not apply to LED bulbs. And thus, many of them do produce those current spikes visible as capacitive reactance.

It becomes a problem as soon you have a whole building illuminated with those nasty things. Your generator is in no case happy about the current spikes. Inverter UPS may even fail. That's why your vendor told you to use a line reactor.

It has to be generously sized to smooth the spikes. The power factor will certainly stay capacitive but that's something a synchronous generator can deliver. Inverter UPS will still give you a headache.

As an alternative, you may want to switch to filament LED bulbs (no capacitor) or high quality LED bulbs with a PFC supply.


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