Sizing a Transformer

[surineman]

I want to size a Transformer for a Water treatment plant.
Should I sum up all connected loads or any factor should be considered?
any material or document reference woulde be appreciated.

Regards

 

[cuky2000]

The simplest method to size a transformer is adding all none coincident loads that will run continuous such as motor load, lighting, heating, computers and miscellaneous loads. Use your engineering judgment to provide additional capacity margin (typ. 25%) to account for uncertainties and future growth.

For a water treatment plant, the motor load probably is the larger among all other loads. An estimate motor load could be determined considering the horsepower, power factor, pump and other equipment efficiency.

Probably a good idea is to have a least a redundant transformer connected to different sources and split the load evenly under normal conditions. One transformer should be capable to run the entire plant without overheating.

 

[AusLee]

Depending on the situation, the 125% of continuous+100% of non continuous can only be one factor in selection:

http://www.powerqualityanddrives.com/short_circuit_transformer/

The Electric code in the countyr of application must have a way to calculate the power estimation for the structure (usage and simultaneity factors chosen according to regulations instead of you taking responsibility). Any factor above 80% of total "installed" load is better than, and hence a conformity, with any requirement i know of.

 

[tinfoil]

A good way to get a reasonable estimate is to find a similar installation and get their actual consumptions/demands, and then add a 'growth factor' (25% is a good one) for a margin. Make sure that you are aware of the client's ultimate requirements as opposed to their intitial or stage one needs.

As already mentioned, a water treatment plant is usually considered to be a critical load. You should allow for redundent transformers and switchgear to ensure no prolonged outages. You may need to talk to the supplying utility about having two different feeders suppying this load (ideally from different substations or different substation buses).

 

[mc5w]

If you can split the load into 2 groups on 2 primary feeders and 2 transformers the transformers will run cooler and live longer. The transformers would only run hot on the few occasions that you need to put all the load on 1 transformer and feeder.