45kv transformer

[domnic]

45kv 3 phase transformer 480 v to /208/120 v is good for 216 amps ?

 

[Besoeker]

45kv 3 phase transformer 480 v to /208/120 v is good for 216 amps ?

At 208V and 216A you have about 78kVA.

 

[Jraef]

45kv 3 phase transformer 480 v to /208/120 v is good for 216 amps ?

No, FLA rating on the 208V side will be 125A. You would need a 112.5kVA transformer for 216A at 208V.

And kV would be the voltage, not the power rating; 45kV means 45,000 volts. I know that's not what you meant obviously, I just can't help myself sometimes...

 

[cadpoint]

I'm trying to gain transformer knowledge as well and have been doing the math myself lately.

45kVA 3 phase transformer 480 v to /208/120 v is good for 216 amps ?

No, you gave both numbers, one number needs to be used and solved for: (a proof for I - 1st) "I" is a known true desired summary number, your two insert numbers are on each side of an equal sign, and no other unknown variables!

kVA = (V * I * 1.732) / 1000

45kVA = (208V * I * 1.732)/1000

45000VA *1000 = 360.256V * I

45000000V/360.256V = 124.911 ~ I : so a 45kVA is way lacking in respect to desired "I"

OR just insert desired AMPs

kVA = (208 * 216 * 1.732)/1000 = 77.815 kVA as answered, One goes up to 112.5kVA transformer size.

schneider < great link of math involved

schneider < great link of transformer sizing

 

[domnic]

45kva transformer

45kva transformer

you are right thank you.

 

[zog]

Actually a 45kVA transformer is good for whatever you want to load it to, how long is the question

 

[rlundsrud]

This is from EC&M magazine, it is an article submitted by Mike Holt regarding sizing transformers. It includes all relevant code citations, OCPD, and primary/secondary feeder calculations. It is hands down the best step my step method I have ever seen, I hope it is helpful.

http://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/TransformerInstallation~20020516.htm

 

[Jraef]

Actually a 45kVA transformer is good for whatever you want to load it to, how long is the question

And if you apply 45kV to the primary of a 480-120/208V 45kVA transformer, the time is going to be very short...

 

[GoldDigger]

Actually a 45kVA transformer is good for whatever you want to load it to, how long is the question

Which means that you probably do not need to size for motor starting amps.
Unless the motor is continuously starting, in which case you will have other problems.