Transformers and PQ Improvement

[skip.delclos]

One of our clients is installing a power conditioning system on a large load (480 volt at the main incoming feeds and MCC's). The system is designed for 480 volt and has been sized properly at the main feeds. However, the 480 v load is stepped up within the building to 4160 as it feeds several large motors (400 Hp). The PF is low (50%), no doubt due to the motors and the transformers. My questions: (1) should the power conditioning system be down-sized at all? and (2) will they still see the full benefits (PF improvement, amp drop, etc.) at the incoming feeds?

 

[skeshesh]

I'm unsure of exactly what power quality improvement method you're using. A bit more detail on the aforementioned "power conditioning unit" would be great. Also, is there one step-up transformer feeding the heady machines or does each machine have a seperate step-up transformer?

 

[skip.delclos]

I believe there are individual transformers for each motor. The power conditioning system is designed around individual units scattered throughout a facility (480 volt max which is why they cannot put them at 4160). Measurements were taken (load, kVAR) to prevent a 'beyond unity' situation. Here, they would be placed at the MCC's feeding the transformers. The power conditioning system is designed differently than traditional capacitor-based systems in that the reactive current is delivered via transformers, not capacitors. The advantage being they are compatible with drives. Hope this helps.

Skip Delclos

 

[Besoeker]

One of our clients is installing a power conditioning system on a large load (480 volt at the main incoming feeds and MCC's). The system is designed for 480 volt and has been sized properly at the main feeds. However, the 480 v load is stepped up within the building to 4160 as it feeds several large motors (400 Hp). The PF is low (50%), no doubt due to the motors and the transformers. My questions: (1) should the power conditioning system be down-sized at all? and (2) will they still see the full benefits (PF improvement, amp drop, etc.) at the incoming feeds?

The very poor power factor suggests that the motors are lightly or very lightly loaded.
Fitting PFC at the incoming feed will improve the power factor as seen by the utility company. Their distribution losses will be reduced.
It may reduce your client's bills if he is penalised for poor power factor but it will do nothing to mitigate conductor losses in his plant.