What is the difference between the motor control type SVC I and SVC V in ATV71?

[DCABANA]

What is the difference between the motor control type SVC I and SVC V in ATV71?

When do I need to select SVC I ? 

[dnordenberg1]

I always wondered the same thing. I think manual said something like SVC I is equal to the behaviour of the older ATV58 drives. But it does not say exactly what this "behaviour" is. As they decided to keep this "legacy" mode it has to have some positive effects too on some loads but I guess it's usage is probably very limited as SVC V was chosen as default.

[PCDTC]

svci is used when you have high demand load with fluctuation, if the motor doesn't have encoder feedback the vfd will manage the current to keep the motor in working as much possible in the optimum current and torque based on motor standard specs . while svcv is only used to keep frequency and voltage control of simple applications like fans , conveyors , ... 

[dnordenberg1]

Sounds like you are referring SVC U like a scalar mode but it is not, both are vector modes. But you might be right that SVC I has advantages in demanding applications. The manual that not say anything about that, only that SVC I mimics the behaviour of older ATV58 drives.

[LeoLazzaro · Accepted solution]

SVC U and SVC I are both open loop vector control . U fluxed by voltage and I fluxed by current.  

SVC U we can say that is the standard vector control with slip compensation , compatible for single and parallel motors( identical motors) . Autotune is mandatory to have good performance , but motor model inside is more flexible and less rigid.

SVC I it is used when high performance control is needed with single motor ( not possible to be used with motor in parallel ) , Motor model is adjusted more carefully  during autotune , optimizing the motor parameters=> basically we have a better motor model inside the drive => better control , it used for application like winder unwinder (torque control) , cranes , high speed or when high dynamic response is needed.

[PCDTC]

svc- i uses current control and this is good for fluctuating loads 

svc- v uses voltage control which is good for torque and frequency precise control of loads 

in general voltage control for general loads is better , in heavy equipment current is better . 

[dnordenberg1]

Interesting! I thought all kinds of vector control required single motor installations. But for me it doesn't matter much anyway since I dislike doing multi motors on a single VSD anyway 🙂 But I'm a bit curious on how the modern modells (320/600/900) hadle the SVC U/I choice since I think the option is now gone, is it SVC U only now?