#123 - Speed control analysis with Sinamics G120 VFD in TIA Portal

There are different ways to program a speed control application with Sinamics G120 VFDs in TIA Portal. Here below a brief comparison between two methods that are commonly used: SINA_SPEED Function Block vs. Technology Objects.

> SINA_SPEED :

    > This Function Block is available for the CPUs S7-1200 and S7-1500

    > The motion control processing happens in the VFD's CPU, which consumes less resources (scan time, memory) from the PLC's CPU. In a PROFINET communication between PLC and VFD, the data exchange in PROFIdrive and PROFIsafe is done through Telegrams that are basically IO maps to specific PLC memory addresses and are able to Write or Read values at these addresses. Telegram 1 PZD 2/2: Standard telegram for speed control

PLC ---> Control Word ---> VFD

PLC ---> Set-Point Speed ---> VFD

PLC <--- Status Word <--- VFD

PLC <--- Actual Speed <--- VFD

PROFIsafe Telegram 30 PZD 1/1: Safety Integrated Functions (Safe-Torque Off STO)

PLC ---> Control Word ---> VFD

PLC <--- Status Word <--- VFD

    > There are variations of SINA_Speed blocks. In these telegrams other drive parameters are exchanged, such as current and torque:

        > SINA_SPEED_TLG352

        > SINA_SPEED_TLG20        

> Technology Objects :

    > This Function Block is compatible with the CPUs S7-1200 and S7-1500

    > In this mode, the core motion control processing happens in the VFD's PLC's CPU, which takes less more resources (scan time, memory) from the PLC CPU. Higher the number of drives in an application, higher it is the impact in the PLC CPU. The resources capacity from the PLC will also depend on the PLC model.

    > Commonly used libraries for speed control with Technology Objects:

        > LAxisBasics library

        > LAxisCtrl library

Note: Each PLC has an estimation of the number of Technology Objects that it can handle. Typically the lower range such as S7-1511 are less capable in comparison to the higher range S7-1518. Speed control application: consumes 40 resources per axis Position control application: consumes 80 resources per axis

Additional resources:

> Siemens example of speed control application

> Siemens example of Safety Integrated Functions

> Siemens example of Library Drive Safe

> Siemens example of Position Control with Safety and Technology Object

> Siemens CPU specs: example of Technology Objects resources limits

> Siemens example of Library Sinamics Extended (LSINAExt)

> Siemens example of STO, SS1 with SINA_Speed