Power Factor Correction

[kdubya]

The traditional solution for PF correction has been to install capacitor banks.
An alternative is a synchronous condenser(SC). One particular manufacturer claims it will maintain unity.
I have not seen any in the field...can someone provide information on their experience with the SC?
Thanks

 

[Besoeker]

The traditional solution for PF correction has been to install capacitor banks.
An alternative is a synchronous condenser(SC). One particular manufacturer claims it will maintain unity.
I have not seen any in the field...can someone provide information on their experience with the SC?
Thanks

It is a rotating machine. A synchronous motor. It can be controlled to run at leading power factor and thus compensate for lagging loads connected to the same distribution system.
The last one I saw used specifically for that purpose was forty some years ago. Yes, I know I'm a grumpy old man.....
We do starters and exciters for such machines - three this month. Two will be controlled to unity pf so offer no correction. The third just might but it's a consequence application rather than a design requirement.

In short, I don't think synchronous condensers are much used these days.
But yes, they can have the ability to maintain unity pf on a system.

 

[StephenSDH]

Learn something everyday.

 

[gar]

100410-0844 EST

See "Alternating -Current Machinery", Bailey and Gault, 1951.

Page 144, Synchronous Condensers. and p145, Power-Factor Correction with Synchronous Motors.

A lot of basic theory in this book. Same book has a chapter (10) on Synchronous Converters.

.

 

[PowerQualityDoctor]

Synchronous motors provides excellent correction of PF, but they are expensive solution to buy and operate (losses).

There are real-time PF systems that can maintain unity power factor. See for example http://www...........)*
**(Link removed...PM PowerQualityDoctor for the link to a specific manufacturer if desired)

 

[LarryFine]

There are real-time PF systems that can maintain unity power factor. See for example http://www.......................

1) Do they reduce the electric bill for non-poor-PF-surcharged (i.e., residential) customers?

2) If so, how?

 

[PowerQualityDoctor]

1) Do they reduce the electric bill for non-poor-PF-surcharged (i.e., residential) customers?

2) If so, how?

Elspec is just an example to PFC that can reach unity power factor (they were the first to do so, nowadays they are not alone but still one of the best or probably the best).

There was long discussion about how PF affects your bill.

To sum up:
1. For residential users - no change on bill (may affect your service utilization, but very minimal).
2. For larger facilities - reduces the losses on the transformer (if owned by the facility) and if the compensation is on distant MCCs, reduces losses on cables. For transformers - the saving are less than 1%. For MCCs - it can be significant, depends on the existing PF and distances. However, PF are usually installed near the transformer.

So why people install PF correction?
1. The utility force them (to improve their own efficiency)
2. Increasing the service utilization
3. Improving power quality issues (like voltage drops)

 

[Besoeker]

So why people install PF correction?
1. The utility force them (to improve their own efficiency)
2. Increasing the service utilization
3. Improving power quality issues (like voltage drops)

One might add to this list savings on capital equipment.
We currently have a project where a couple of synchronous motors are being replaced by cage motors. Each motor has its own unit transformer sized to run the original synchronous machines which had been operated at unity power factor. Unfortunately, power factor of the new motors is fairly low and that would have taken supply kVA beyond the rating of the unit transformers. Obviously PFC was a solution. Without it new transformers would have been required. The supply cabling from the HV switchgear would have had to be uprated - not an insignificant cost considering it is a run of about 200m of 11kV XPLE for each. That alone would have been around ten times the cost of the PFC.

 

[PowerQualityDoctor]

One might add to this list savings on capital equipment.
We currently have a project where a couple of synchronous motors are being replaced by cage motors. Each motor has its own unit transformer sized to run the original synchronous machines which had been operated at unity power factor. Unfortunately, power factor of the new motors is fairly low and that would have taken supply kVA beyond the rating of the unit transformers. Obviously PFC was a solution. Without it new transformers would have been required. The supply cabling from the HV switchgear would have had to be uprated - not an insignificant cost considering it is a run of about 200m of 11kV XPLE for each. That alone would have been around ten times the cost of the PFC.

That's what I meant at item #2, but reading it again showed me that it was not as well elaborate as yours... The two selling point for real time PFC is service utilization and power quality issues.