Does my motor control book have an error?

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zappy

Senior Member
Location
CA.
So the left picture shows the Overload contacts as normally closed, on the right picture it shows the circuit going through the normally open overload contacts. Am I missing something here? Thank you for your help.
 

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Tulsa Electrician

Senior Member
Location
Tulsa
Occupation
Electrician
Looks right to me.
Edit.
Looking at the bottom pic I see what you mean. I was looking at the first pic of the wiring diagram.
 
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TwoBlocked

Senior Member
Location
Bradford County, PA
Occupation
Industrial Electrician
IMG_9845 is in error. The NC overload contacts must be used, terminals 95 & 96. If the NO overload contacts are used, the only way the motor could be started and run is if the overload was manually tripped. This would allow the motor to continue running if an overload condition should occur. The NO overload contacts (term 95 & 96) should only be used for indication.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
This may be due to the difference between normal contact position when de-energized and when in use.
 

Tulsa Electrician

Senior Member
Location
Tulsa
Occupation
Electrician
Here this should clear it up.
 

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TwoBlocked

Senior Member
Location
Bradford County, PA
Occupation
Industrial Electrician
I'm not seeing what you see. Can you help me
Top left is a table explaining the numbering system (Sure would like to see a complete, official one.) Bottom left is a diagram showing the contacts in a schematic. The table says 95 & 96 are NO, the diagram shows 95 & 96 as NC.

I used to do electrical design at a manufacturing plant and I notice stuff like that. Sooooo nice to be back in the field, even with a boss that is, er, simple-minded.
 

Tulsa Electrician

Senior Member
Location
Tulsa
Occupation
Electrician
Top left is a table explaining the numbering system (Sure would like to see a complete, official one.) Bottom left is a diagram showing the contacts in a schematic. The table says 95 & 96 are NO, the diagram shows 95 & 96 as NC.

I used to do electrical design at a manufacturing plant and I notice stuff like that. Sooooo nice to be back in the field, even with a boss that is, er, simple-minded.
Thanks, I will review again.
 

Tulsa Electrician

Senior Member
Location
Tulsa
Occupation
Electrician
I enjoy learning new things.
I reviewed the table.
Could you give me an example how this would be applicable. I have used these for singling. Never for anything else.

I'm also aware these numbers can be used elsewhere other than the over load block N.O.
For other control items based on the symbols in table.

I would not think in this case it's applicable for the OP question. However I'm willing to learn.
Thank you in advance.
 

TwoBlocked

Senior Member
Location
Bradford County, PA
Occupation
Industrial Electrician
I enjoy learning new things.
I reviewed the table.
Could you give me an example how this would be applicable. I have used these for singling. Never for anything else.

I'm also aware these numbers can be used elsewhere other than the over load block N.O.
For other control items based on the symbols in table.

I would not think in this case it's applicable for the OP question. However I'm willing to learn.
Thank you in advance.
Gosh, sorry, I am trying to understand what you are asking. I enjoy a good conversation about electrical documentation. "I have used these for singling" Don't know what you mean. Can you give an example?

I think the IEC numbering system is very applicable for the OPs question. Finding that table, although having a typo, gives me some info I'd been looking for for a while: First digit means what set the contacts belong to, with 9 reserved for timers and overloads. Second digit whether NC (1 & 2, 5 & 6) or NO (3 & 4, 7 & 8). With that info, you'd know that terminals 97 & 98 are for NO contacts on a timer or overload. In the OPs question, since this is on an OL block, it indicates that the second illustration is wrong.

I have been confused many, many times by what these IEC terminal numbers mean (along with other systems). I just drag out the documentation or my meter to figure it out when designing, or installing, or troubleshooting.

Still would LOOOVE to see a table of the terminal numbers, especially one that compares the different systems. I've looked, but never in the right place I guess. Maybe a new Topic?
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Top left is a table explaining the numbering system (Sure would like to see a complete, official one.) Bottom left is a diagram showing the contacts in a schematic. The table says 95 & 96 are NO, the diagram shows 95 & 96 as NC.

I used to do electrical design at a manufacturing plant and I notice stuff like that. Sooooo nice to be back in the field, even with a boss that is, er, simple-minded.
That's a quirk of the concept of "normal". In IEC world, the 95/96 contacts are in fact "normally" open, held closed by a spring loaded mechanism tied to the OL thermal element. If the thermal element releases the trip bar, the contacts RETURN to their "normal" state of being open.

I grew up on NEMA, went to work for a German company (Klockner-Moeller), had to have my brain rewired on this issue (among others)... But being Germans, they had it ALL documented in excruciating detail, a process they referred to as "rationalization". They had VOLUMES of binders for us EEs to use if we had any questions, called "PR" manuals, standing for "Planen und Rationalisierung" (Planning and Rationalization in German). No detail was left unexplored and dissected to the Nth degree.
 

TwoBlocked

Senior Member
Location
Bradford County, PA
Occupation
Industrial Electrician
That's a quirk of the concept of "normal". In IEC world, the 95/96 contacts are in fact "normally" open, held closed by a spring loaded mechanism tied to the OL thermal element. If the thermal element releases the trip bar, the contacts RETURN to their "normal" state of being open.

.....
That does not explain why the table says one thing and the diagram shows another.
 

Mr. Serious

Senior Member
Location
Oklahoma, USA
Occupation
Electrical Contractor
Still would LOOOVE to see a table of the terminal numbers.
I looked. It's Sunday so I'm not supposed to do anything, but still it's frustrating to look and look and look without finding it, so I'm posting what I found so far, then I'm giving up.

I thought I had seen it before. But it turns out, the one I have seen before is for automotive wiring and the numbers have completely different meanings. Here is one such reference on the Internet Archive: Automotive component pin assignments.

As far as what we're actually looking for, these are what I found:
  • There is a document from Siemens from June 2010 called "Terminal markings for IEC contactors and relays." This may be the best resource. It had a couple of accolades on a thread in a PLC forum thread from August, 2011. But I was only able to view the first page on Scribd and didn't find any other copy anywhere.
  • There's the reference you already posted in replay #16 with the incomplete list.
  • There's an ABB document, "Terminal Marking and Positioning." It is apparently section 8 of the ABB Low Voltage Products manuals, document number 1SBC100122C0202. I didn't see any list of terminal numbers, per se, but it does have explanations of terminal markings on all their low-voltage products, and it also lists standards that these markings come from: generally IEC 60445, IEC 60947-1 and EN 50005. Additionally,
    • – IEC 60947-4-1, EN 60947-4-1 and EN 50012 for contactors and their auxiliary contacts,
    • – IEC 60947-5-1 and EN 50011 for contactor relays,
    • – IEC 60947-4-1 and EN 60047-4-1 for overload relays.
  • An Eng-Tips forum thread Numbering of contactors and relays in wiring diagrams also lists some of the above standards as well as referencing IEEE-315. I didn't try looking that one up.
 
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