×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

FLA Rating calculation on stand alone rbt mig welding cells

FLA Rating calculation on stand alone rbt mig welding cells

FLA Rating calculation on stand alone rbt mig welding cells

(OP)
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.

RE: FLA Rating calculation on stand alone rbt mig welding cells

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.

RE: FLA Rating calculation on stand alone rbt mig welding cells

(OP)
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.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources