Mains power factor correction and diesel generator

It depends whether power factor correction is capacitive or inductive.

From This white paper by Jim Iverson, Senior Applications Engineer:

"Power factor (PF): Capacitive loads, overexcited synchronous motors, etc. cause leading power factor, where current leads voltage. Generators have a very limited capacity for supplying leading power factor loads. If not controlled, these can
lead to loss of voltage control and damage to the generator. Lagging power factor, where current lags voltage, is more generally the case and is a result of the total inductance of the circuit. Power Factor is the ratio of kW to kVA and is expressed
as a decimal figure (0.8) or as a percentage (80%). Three-phase gensets are rated for 0.8 lagging PF loads and single-phase gensets for unity power factor loads. Lower power factor loads require larger alternators or gensets to properly serve the
load."

This indicates that the correction is required in the cct.

It also depends whether the correction is for the load, or supply lines.

A correction for load will bring the loads close to PF of 1. The only way I can see this as a problem is if a capacitor in the correction feeds back to the automatic switching ccts after power is lost. There are switches specifically designed to handle live switching.

If it is for the power lines, yes it needs to be switched out, but more likely it is for your load matching.

If it is for the power lines, it belongs to the power company. In this case simply have the connection point for switch over to your generator after the PF correction unit.

I need to know more details

1) Whether the power factor bank is switched on after the diesel generator talkes over the load.

2) Is it automatic or manual

3) I sit always switched on even if there is no load.

It is generally recommended to have after the genertaor reaches its peak and connected to bus bar.

I want to connect a power factor correcting equipment with my 591 kva diesel Generator to improve its p.f from 0.8 to 0.98. Then what will I have to do?

Find someone locally who can do it. Internet search, then telephone, perhaps?

True, but it depends on power factor KVA rating vis a vis Generator reading. When you start the Genset and have not loaded it yet then all the loading will be capaciatnce from the Genset , if the panel is directly in contact with powerfactor correcting device. After you have taken the Loads in the generator , you can use the Powerfactor correction with Genset. Generally Generators are rated with lower Power factor , say 0.8 when they show the KVA rating with respect to the Kw power of the Engine . So, if the KW power of Engine is 100Kw , then the Alternator Rating is given as 100/0.8 = 125 KVA. So it is better the power factor correction panel has a switch unit also. After loading the set with the loads it is to take , then PF corrector switched be made on.

Provide a transfer switch wiring scheme that cuts out the capacitor bank, if possible, when the generator is running. And yes it can damage the generator.

Been there ... done that. Unless you are connected to the utility company source, you better have a place for capacitor vars to go. If you don't... the vars will try and feed back to the generator and mess it up. Automate the capacitor or keep it off.

Capacitor Bob

The cap bank should have a disconnect switch/contactor on the primary sie. Loop the control voltage for that device through the EG ATS or breaker scheme secondary contacts this will disconnect the caps as long as the EG is supporting the load.

Note: Caps need to have a way to bleed off excess voltage. If you don't bad things could happen when they reconnect.

hello friends, pls tell me why it is not advised to operate PFC capacitors and gensets together, what is the biggest drawback? There are so many idea but pls tell me the real ones..

If automatic power factor correction equipment is used ,it can be connected to gensets also without over loading gen set. As a precaution PF Value can be set at.95 when on gen set.

You do not want the power factor (to be supplied by the Gen) to go into leading mode. The armature magnetic field leading the field is a bit bad for the stability of the Gen. There are quite a few papers on this aspect. Keeping it too near the generator may land up in this problem and you may have problem in controlling the hunting.