Shear circuit

Electron_Sam78

Electron_Sam78

Senior Member
Location
Palm Bay, FL
Hey all, give me your thoughts on circuit size and OCPD for this shear I’m wiring for a metal dab shop. The main motor is 30kw which is 40.3 HP. The full load of the whole machine is 180 amps. I’m thinking wire for the full load amps listed in the data plate and OCPD for the largest (main) motor which would be 300a according to chapter 4. FYI, the main motor is not on a VFD in the control cabinet so it does have the full inrush to deal with. The weird thing is the “nominal current” of 120a. I can’t say I’ve ever seen a nominal current and a full load current listed. Not sure what it means in relation to wiring the circuit. This thing is made in Turkey. Thoughts?
 

Attachments

  • IMG_4373.jpeg
    IMG_4373.jpeg
    1.3 MB · Views: 21
Electron_Sam78 said:
FYI, the main motor is not on a VFD in the control cabinet so it does have the full inrush to deal with.
Click to expand...
Why would you say it does not have to deal with the full inrush because it is NOT on a VFD? Seems backward in one way or the other.

Per our rules, the nominal current is irrelevant. You only deal with the rules that apply here. If there is only the one motor, you size the branch protection based on the FLC from the NEC tables, using the closest HP value, in this case 40HP. If there are multiple loads inside the machine and this is just the main one, then there is a formula for determining the feeder size, but you will also need to know that the individual loads have proper branch protection in their control panel (if any).

This is one one of the problems with people importing electrical machinery without making sure it is listed by an acceptable NRTL here. Listing would have required the relevant data be included on the nameplate. Hopefully you are not going to run into issues relating to installing unlisted equipment.
 
Jraef said:
Why would you say it does not have to deal with the full inrush because it is NOT on a VFD? Seems backward in one way or the other.

Per our rules, the nominal current is irrelevant. You only deal with the rules that apply here. If there is only the one motor, you size the branch protection based on the FLC from the NEC tables, using the closest HP value, in this case 40HP. If there are multiple loads inside the machine and this is just the main one, then there is a formula for determining the feeder size, but you will also need to know that the individual loads have proper branch protection in their control panel (if any).

This is one one of the problems with people importing electrical machinery without making sure it is listed by an acceptable NRTL here. Listing would have required the relevant data be included on the nameplate. Hopefully you are not going to run into issues relating to installing unlisted equipment.
Click to expand...
I said it does have the full inrush to deal with. Yes there are other loads in the machine. Two adjusting motors with their respective VFDs. Control transformers, relays, PLC. The components are protected inside the control cabinet.
 
Last edited:
That install would be tricky here. As Jraef points out, the lack of a NRTL label and the missing pertinent data such a control panel SCCR would raise major red flags.
 
augie47 said:
That install would be tricky here. As Jraef points out, the lack of a NRTL label and the missing pertinent data such a control panel SCCR would raise major red flags.
Click to expand...
It’s in a military base so they don’t care. I’ve worked in several foreign machines, just never come across the term “nominal current” listed in addition to “full load current”.
 
Electron_Sam78 said:
It’s in a military base so they don’t care. I’ve worked in several foreign machines, just never come across the term “nominal current” listed in addition to “full load current”.
Click to expand...
I would think nominal would refer to the expected Normal running current, where Full Load would be the maximum. Maybe it is like our nameplate and our SF values.
 
jim dungar said:
I would think nominal would refer to the expected Normal running current, where Full Load would be the maximum. Maybe it is like our nameplate and our SF values.
Click to expand...
Seems that way to me as well. But it’s still confusing with multiple values listed. The documentation is no help. I’m leaning towards wiring for the full load current listed on the data plate.
 
“Nominal current” is what is often called “RLA” (Running Load Amps) here, which is useless from an BEC standpoint. So per OUR rules, when a machine only lists the RLA, they then must ALSO list the MCA and MOCP for you. But again, since you are not dealing with a machine that was listed by an NRTL, you don’t have that.

However since they DID also list the FLA, you can just ignore the Nominal Current, it has no official use here.
 
You must log in or register to reply here.
Top