Powerfactor Control

What is the PF for the site? If that needs improving then start to look at individual drives. Correction to a 75hp motor isn't going to make that much difference.

PS what is a "certain industry"

PPS why .98, to do it costs more than it's worth, .9 is a realistic figure

I suspect that you are measuring power factor wrong. Adding a properly sized capacitor will always change the phase angle of the current drawn from the source. I suspect that you continue to be reading the current being drawn by the motor and not the motor and capacitor combination.

_{I suspect this because I've done it. It was very embarrassing.}

You and me both

Took the PF corection connection before the CT.... Ooopps

TonyS Quote "PPS why .98, to do it costs more than it's worth, .9 is a realistic figure"

Not always. I depends on the utility charge for KVA. 0.98 might be a stretch but 0.95 may be worth the expense. It would also depend on the plant total power factor.

try E-save,look it up.

Junk. This device, and all others like it, does NOTHING to improve the pf of the motor. They also don't really save anywhere near as much energy as their lies state.

Don't be a sucker...

Connecting Power Factor Correction Capacitors directly to motor terminals is recommended ONLY if the motor load is constant. Because, the kVAR rating for motor PF improvement is calculated based on the name plate power factor of the motor as existing power fcatopr and for any desired PF (say, 0.95). But, the power factor given in the name plate is true only when the motor is delivering its rated load. In under-loaded conditions, the power factor would fall drastically and all the PF improvement calculations would be erratic then.

Also, another very important point to note in case of individual compensation (direct connection of PF improvemnt capacitors to motor terminals) is that the rated current of the capacitor MUST be less than 90% of the no-load current of the motor. Otherwise, when the power supply to the motor is switched OFF, the stored energy in the capacitor wouldm "self-excite" the motor and as the motor shaft is still in motion due to inertia, it would function as an "induction generator". The worst case voltage developed could go as high as twice the rated motor voltage, which is sure to damage the motor and the capacitor.

I strongly suspect that this is the resaon for your repeated capacitor failure. Please check the above and I am sure, your capacitors would survive.

I feel suspicious about the way you tried the PF improvement, its better you provide us a sketch as how exactly you where trying to do it, all can provide you more accurate inputs on your trial.