Dear all,

I am programming some S200s and for the first time (don't ask me why) I have noted that when I read the r81 (Torque usage), the value I get is completely wrong.

I have a 3Nm motor and torque (r80) is about 1 Nm so r81 shoud be aroud 33% approx. But it is lower and lower, like 6-8 %. Why ? Because it seems to be "rescaled" to a fantasy parameter called P2003 which is by default 16 ( !!! ) Nm.

Why, why and again why in a system where you declare the motor (in the configuration), so it knows perfectly motors data... Why that system invents the P2003 and sets it to 16 Nm ? Why automatically it does not set it at 3 Nm (in my case) ?

Now I have to read motor rated torque and write it with my PLC in P2003, in order to get the important r81 parameter working...

A complete running in circle thing that Siemens could easily avoid us.

Is this necessary ?

Your image doesn't sound any bell here since we are talking about how torque usage is rescaled.

I asked why p2003 is automatically set at 16 Nm, regardless of the motor. My motor is a 3 Nm and p2003 (instead of being 3 Nm) is 16.0 Nm.

This means receiving a Torque Usage which is totally wrong.

This means that if you forget to set properly the p2003 when you do commissioning, you are in troubles if r81 is important for your machine.

Why p2003 is not automatically taken by motor's data  ?

Davinator

Your image doesn't sound any bell here since we are talking about how torque usage is rescaled.

I asked why p2003 is automatically set at 16 Nm, regardless of the motor. My motor is a 3 Nm and p2003 (instead of being 3 Nm) is 16.0 Nm.

This means receiving a Torque Usage which is totally wrong.

This means that if you forget to set properly the p2003 when you do commissioning, you are in troubles if r81 is important for your machine.

Why p2003 is not automatically taken by motor's data  ?

Then let me explain it to you. On the image the characteristics are shown for a 1.9 Nm motor. For that motor 100% of available torque is 12 Nm. And that's more or less what is set in p2003.

So, yes, it is taken from motor's data. Automatically.

On the other hand, r81 has nothing to do with p2003. Simplifying things, it is defined as r79/r1538*100%

jacek d

 

Then let me explain it to you. On the image the characteristics are shown for a 1.9 Nm motor. For that motor 100% of available torque is 12 Nm. And that's more or less what is set in p2003.

 Sorry, how can you say that for a 1.9 Nm motor the 100% of available torque (which IS 1.9 Nm) is "more or less" 12 Nm ? Is 631% more ! You think that a tiny 1.9 Nm motor can give up to 12 Nm ? 

unknown user

So, yes, it is taken from motor's data. Automatically.

 Yes, and it is completely fantasy, since (super)overestimating the available torque is something that is pointless. A X Nm motor can give nominally (100%) a torque of X Nm, end of the story. If you speak about Allen Bradley then ok, these motors are X Nm but can have a 3X Nm peak torque for a very short period of time. But nevermind 6 times the nominal torque.

unknown user

On the other hand, r81 has nothing to do with p2003. Simplifying things, it is defined as r79/r1538*100%

 Ah yes, I see that r81 is calculated automatically from there.

Since everything is automatically calculated and "taken from motor", why r81 is completely wrong then ? You can try yourself : if you do not recalculate the r81 using the real torque of the motor, you will have a fake (and VERY underestimated) torque usage.

Davinator

Sorry, how can you say that for a 1.9 Nm motor the 100% of available torque (which IS 1.9 Nm) is "more or less" 12 Nm ? Is 631% more ! You think that a tiny 1.9 Nm motor can give up to 12 Nm ? 

You are right. It can't. Due to a motor module used it is limited to 10-11 Nm. Up to its nominal speed.

I think your understanding of nominal torque of a motor is incorrect.

jacek d

 

Davinator

Sorry, how can you say that for a 1.9 Nm motor the 100% of available torque (which IS 1.9 Nm) is "more or less" 12 Nm ? Is 631% more ! You think that a tiny 1.9 Nm motor can give up to 12 Nm ? 

You are right. It can't. Due to a motor module used it is limited to 10-11 Nm. Up to its nominal speed.

Lol, sorry, probably I did not understand. You really think that a one point nine Nm motor can give 10-11 Nm ?

unknown user

I think your understanding of nominal torque of a motor is incorrect.

 Maybe, but if you think that it is correct to say that torque reference for a 1.9 Nm is 11-12 Nm then I think that I am not the only one to have an incorrect concept of nominal torque.

I have attached the data sheet of your 1.9 Nm. Can you show us where it should give out 10-11 Nm ?

Oh please.

Davinator

Lol, sorry, probably I did not understand. You really think that a one point nine Nm motor can give 10-11 Nm ?

This is "my" motor - 1FT7036-5AK70-1FH0. Yes, it's rather high end. Actually its nominal S1@100K torque is 1.7 Nm - my bad, I've read its approx nominal torque from the chart at first. Sorry for that. 

To achieve this level of performance an S120 ALM @ 480V and appropriate MM are required.

Anyway, putting aside discussion what is feasible and what's not, please read the fancy manual to understand how p2003 is calculated. Spoiler - it has something to do with max motor current and its torque constant. 

BTW, nominal torque of a motor you presented is 1.27 Nm.