Install capacitors to improve pump motor PF

I have 3 pumping motors of 1750 kw 6.6kv, with soft starter they are maintaining a pf of .96-.97. Now I want to install HT capacitors to use these motors in d.o.l, can I take the pf to .99 using this?

Your pf is very good as it is right now. I am assuming you are measuring the pf at the PCC (Point of Common Coupling) with the utility? I do not recommend that you do anything. I do not know nor have I seen you mention if you already have a capacitor bank or not, but anything at or above .95 is considered very good. I never recommend installing caps if the pf is >.90. It's not worth it both from a ROI and a maintenance standpoint. You want some "headroom" for 3 basic reasons: 1) if you go past 1.0, you will have a leading pf and this can place undue stress on the utility's transformer serving you. 2) if the utility has directional relaying in their substation, there is a much smaller margin for leading pf than lagging pf. So utilities do not want customers to design too close to 1.0 because they are likely to go over. Going over is easy to do because of the operating dynamics within a plant. The pf may fluctuate by .05 (or more) at various times throughout the day. If every customer went above a pf of 1.0, it would be very bad for the utility because nuisance tripping would occur. 3) if you are on a "kw rate" with the utility, you are likely not penalized as long as you are above a pf of .90.

You will do better by focusing on the efficiency of your equipment how it is operated and the maintenance of your equipment than trying to tweak your pf by .03. But if you decide to install a capacitor bank anyway, you need to talk with your utility and make sure you do not cause any harmonic resonance and get them to help you with what your ROI will be. By the way, you may also have to install line reactors at each soft starter (and at all VFD locations) if you do not already have them.