Transformer total cost of ownership

Status
Not open for further replies.
electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
I found this formula from a utility bid spec sheet and though it was interesting.

TOC = PRICE + NL WATTS* 4.50 + LL WATTS* 1.575

where

TOC = Total ownership cost
PRICE = Purchase price quoted
NL WATTS = quoted no-load losses in watts
LL WATTS = quoted load loss watts

I have a step up step down transformer setup at my house, and have done several for customers and the losses are certainly a huge consideration., particularly when used transformers can often be had quite cheaply, but they have significantly more losses than new units. I have three 15kva units at my house and the no load losses range from .4% for my newest DOE 2016 unit, to 1% for an older unit. This formula of course doesnt seem appropriate for a retail rates. Im thinking of multiplying those NL and LL constants by about 4 for retail rates. What do you think? Clearly NL losses are easier to amortize than load losses.
 
I think that by oversimplifying the calculation, and casually mixing incompatible units, (dollars & watts) they've ended up with a formula that yields the right answer only for a very narrow (and likely now obsolete) set of local circumstances.

Start from scratch, account for everything, use consistent units (hours for transformer life, probably) keep the units attached to the variables, plug in your actual* energy use & cost, and you'll get the right answer.

* best estimates, of course
 
electrofelon said:
Good question, it doesnt say. This was from a utility for the procurement of new transformers, so I imagine quite a long time.
Click to expand...
Don't forget the estimated time the transformer is actually loaded. This is a big deal for transformers that idle for most of their life and partly why the DOE evaluates efficiency at 35% loading.

I would not be surprised to find a utility calculating no-load losses at 100% of the time and an average load losses at 50% loading.
 
Don't forget to factor in the quality of life issue: How much can you stand to hear a transformer humming while you are trying to sleep?
 
Try this:
electrical-engineering-portal.com

Life cycle cost of transformers

To perform the economical analysis of transformer, it is necessary to calculate its life cycle cost, sometimes called total cost of ownership, over
electrical-engineering-portal.com electrical-engineering-portal.com

There are also other variables depending on which side of the meter you get the power. Different rates, FV of money, maintenance needed, etc..
Wholesale blocks have different rates, along with the super expensive peak demand which has to be accounted for but is just an experience guess.

On the retail side for your transformers there is TOU rates if your on them, or any other specialized rate structure your POCO may have and you are on.

heres another one
 
Hv&Lv said:
Try this:
electrical-engineering-portal.com

Life cycle cost of transformers

To perform the economical analysis of transformer, it is necessary to calculate its life cycle cost, sometimes called total cost of ownership, over
electrical-engineering-portal.com electrical-engineering-portal.com

There are also other variables depending on which side of the meter you get the power. Different rates, FV of money, maintenance needed, etc..
Wholesale blocks have different rates, along with the super expensive peak demand which has to be accounted for but is just an experience guess.

On the retail side for your transformers there is TOU rates if your on them, or any other specialized rate structure your POCO may have and you are on.

heres another one
Click to expand...
Good info, thanks.
 
Status
Not open for further replies.
Top