Transformer sizing

[hobledogee]

I have a customer looking to replace their wine cooler unit. The existing unit is 460v/3. The new unit will be 203/1. I looking for help on transformer selection, what kVA is necessary. The unit has a mca of 12.1 amps, mfs 17.6 amps, lra of 49 amps, rla of 12.1. I was told I would need a 15kva transformer, does that seem correct?

 

[cpinetree]

5kva single phase 480v to single phase 240v will give you 21amps at 240v

Here is a link for simple transformer calculations: https://www.t-r.com/transformerCalc.php

 

[Ingenieur]

208/1

are the currents for the new unit?
using the 17.6 A kva = 3.7 kva
a 5 kva 480/1:208/1 (or 240) should be plenty

using the mca 12.1 a 3 kva should do it

page 6 http://download.schneider-electric....File_Id=3331349907&p_File_Name=7400CT9601.pdf
480/1:208/1 3 kva (or 5 kva)

 

[Ingenieur]

if the ratings are for the old 480/3 unit
using mca 12.1 A, 10 kva
using mfs 17.6 A, 15 kva

 

[Julius Right]

If the HVAC unit was supplied with 3 phase 480 V 12.1 A then the VA required was
sqrt(3)*480*12.1=10000 VA[10 kVA]
If this required VA will be supplied with single phase 240 V the current will be 10000 VA/240 V=41.7 A.
The transformer has to be 10kVA rated [for continuous load] 480/240 V.
In my opinion, mfs [maximum fuse or HACR circuit breaker size] is stated in order to overcome
the starting process. If the transformer overload will be 1.25*41.7 A=52 A will not trip before mfs.

 

[dionysius]

I have a customer looking to replace their wine cooler unit. The existing unit is 460v/3. The new unit will be 203/1. I looking for help on transformer selection, what kVA is necessary. The unit has a mca of 12.1 amps, mfs 17.6 amps, lra of 49 amps, rla of 12.1. I was told I would need a 15kva transformer, does that seem correct?

Please rephrase since not clear what the numbers refer to (old vs new) and do you mean 203/1 or 208/1 or 230/1 for new unit v???

 

[dionysius]

Is it worth stating that a slo-blo OCPD (type D trip curve) should be specified for this application????