FLA Rating calculation on stand alone rbt mig welding cells 1

[WIRESRCROSSED]

Disclaimer: for personal education & clarification only

I am having difficulty recalling the reasons behind the FLA rating of a stand alone robotic mig weld with DC mig power supply is so much lower than the designed fuse system...


For example, 3 phase, 575V, 100A fused disconnect, 75 KVA (575V-208V xfrmr) with 3 rbts & weld supplies branched from it, other 3ph motors & 575V-120V xfrmr. I have worked out all the fusing & wire sizing based on current draws & maximum protection & code...but, when supplying the FLA rating for the service drops, based on past jobs of reference the FLA would only be approx. 25 A.

I understand that the rbts & weld supplies are not in constant use & if I measured with an ammeter, it would probably be lower than the 25A value, but I would like some theory background as to why the FLA rating is so low. Would the customer not service this machine with wires & fusing based on the lower FLA rating & not on the actual main fused disconnect?


I would appreciate any advice or sites to reference.

 

[laundry]

WIRESRCROSSED.
Im not quite sure what you are getting at but a 75kva load roughly is 130amps ie 75000/575=130amp. Iwould think the manufacturer as stated that the systems requirements are 75kva on FL. So your disconnector and fusing are designed for this potential load.
Not mush point fitting under size cable and disconnector when next week you draw 100amps.

Barry.

 

[WIRESRCROSSED]

Just to reply to your reply laundry,

I have decided to measure the machine's amperage draw at full working capacity & use it as a guide to the FLA rating on the machine's tag. From experience the weld cell will draw current considerably lower, but does have the capacity to do higher when pushed into high production.


Thx anyways, I know the wording was a little confusing.