# Can 150KVA transformer withstands 360A input current



## MIMA (May 10, 2021)

My company is planning to install a new controller box (Spec: DCE1800) for welding machine.
But, currently we still in process to decide the size of transformer to control DCE1800

After discussed with machine maker, they said the 90KVA is enough to control the DCE1800. 
so we decide to use 150KVA transformer.

But, I am concern about the capability of the transformer to withstand maximum of 360A input current that only flows for 15ms? would this current could affect the quality of the welding result?

Thank you in advance for the advises


----------



## paulengr (Oct 8, 2017)

240 x 360 / 1000 = 86.4 kVA. This is WAY under the 150 kVA rating. It will barely be loaded. Unlike most equipment transformers can and do take temporary loads above nameplate without damage. The short circuit limit is the kVA divided by the impedance (%Z) which on a small one like that might be 50 times it’s continuous load rating although the voltage will be very low by then.

Usually I start to check if you will be blowing fuses when you overload it but you aren’t overloading. In fact 100 kVA is plenty. With 150 depending on how the welder cycles it might be enough for two.

15 ms is one power cycle.


----------



## just the cowboy (Sep 4, 2013)

It is the welder manufactures call. What size xformer do *they *recommend for the machine they have done this before.

For anything else it would be overkill if it was just for one machine, most motors not care but you have a concern about the weld. If it is not for the one machine go for the bigger one you may need it in the future.

Cowboy


----------



## MIMA (May 10, 2021)

paulengr said:


> 240 x 360 / 1000 = 86.4 kVA. This is WAY under the 150 kVA rating. It will barely be loaded. Unlike most equipment transformers can and do take temporary loads above nameplate without damage. The short circuit limit is the kVA divided by the impedance (%Z) which on a small one like that might be 50 times it’s continuous load rating although the voltage will be very low by then.
> 
> Usually I start to check if you will be blowing fuses when you overload it but you aren’t overloading. In fact 100 kVA is plenty. With 150 depending on how the welder cycles it might be enough for two.
> 
> 15 ms is one power cycle.


Thank you for the reply,
Sorry I forgot to mention the input voltage to the transformer. it is 400V. 
So it will be 400 x 360/1000 = 144KVA right? But, since we plan to use 3 phase transformer, the KVA become 1.73times bigger right?

Actually the maker said that 90KVA could control the welding machine with stable. The 360A is maximum input current to controller during welding process and the duration for this current to flow is 15ms. Is this meant by power cycle?


----------



## MIMA (May 10, 2021)

just the cowboy said:


> It is the welder manufactures call. What size xformer do *they *recommend for the machine they have done this before.
> 
> For anything else it would be overkill if it was just for one machine, most motors not care but you have a concern about the weld. If it is not for the one machine go for the bigger one you may need it in the future.
> 
> Cowboy


Thanks for the reply
The manufacturer said that 90KVA should be enough for the welding machine to function with stable. 

For the machine side, we plan to use the DCE1800 to control 2 pcs of welding head.


----------

