Siemens Sinamics G120C fixed speed setpoint

[mulderm]

Hello,

I use a Siemens Sinamics G120C inverter in combination with a S7-1200 cpu.
I use the Main Setpoint with the Providrive option and send 1810 rpm to the inverter.
Now I use r722.3 digital input to select a fixed speed of 300 rpm.
But when I activated this input the totaly speed will be 2110 rpm, the fixed speed will be added.
See attachment.
I can calculated to get 300 rpm but when the main setpoint changes I get another speed then 300 rpm.
So independent of the main setpoint via Profidrive (I must use this for other situations) when I activated r722.3 always the drive must be 300 rpm.
Who can help me to fix this?

Thanx, mulderm

 

[Ken Moore]

So, from the diagram, the "fixed" setpoint is added to the main setpoint. If you add a negative number do you get 300 rpm? If so, can you do logic in the PLC to get the fixed setpoint. (Main SP - 300) * -1 = Addition SP

 

[JRW]

Use the free blocks with a NSW switch

https://cache.industry.siemens.com/...tt_868222/v1/85168215_FAQ-01X4QJPN_FFB_en.pdf

 

[mulderm]

So, from the diagram, the "fixed" setpoint is added to the main setpoint. If you add a negative number do you get 300 rpm? If so, can you do logic in the PLC to get the fixed setpoint. (Main SP - 300) * -1 = Addition SP

Hello Ken,
Yes that is right.
I add a negative number on it and then I get 300 rpm.
But when the main setpoint changed I get no 300 rpm.
I think I can't send the fixed calculation to the inverter, it is adjusting in the settings.

Greetings,
mulderm

 

[mulderm]

Use the free blocks with a NSW switch

https://cache.industry.siemens.com/...tt_868222/v1/85168215_FAQ-01X4QJPN_FFB_en.pdf

JRW, thanks for helping,

But where are the free function blocks?
Where can I find it in the G120C parameters function diagram?
And how will I make this for my problem?

Thanks,
mulderm

 

[mulderm]

Hello JRW,
I have investigate your info.
I think I understand, l will test.
Thanks.

Greetings,
mulderm

 

[JRW]

They are easy to use

Post your specific questions

Also
You can map r722 io back to the plc too
And do the logic in the plc …

If you find writing it the pic better for you

 

[mulderm]

JRW,

I am on the good way, it works with the free function blocks.
See attachment.
Goal is to start a motor with the profidrive setpoint and after a time I will
give the motor a slow speed and then after a setting time the motor must be stopped.
Then after a few seconds the motor start again.
Problem is that I use OFF1 to stop the motor, but I want to give a 0 rpm in the settings or free function blocks but I don't know how to do that.
Now the inverter stops every time and also the fan, I don't want that.
I will use a setpoint of 0 rpm to put this without using in the plc-program
Can you help me with the blocks?

Thnx,
mulderm

 

[mulderm]

JSW,

I think I found it, see attachment.
I will test this.

Greetings,
mulderm