AC drives
Home » Blog » AC drives » Variable frequency drive Vector control VS V/F control

Variable frequency drive Vector control VS V/F control

As far as I know all variable frequency drives with vector control can also be run with just V/F control.

A drive in vector control mode has several tuning parameters to increase or decrease motor performance. With factory default parameters a VFD in vector mode will have higher performance than a drive in V/F mode. Sort of like a "sport or racing" computer option in a modern automobile.

Depending on the application using vector control can use a lot more power. If you have a rapidly surging load the vector may be really struggling to keep the speed constant while a variable frequency drive in V/F mode never notices the speed change. If the application has a steady mid-range speed and load or has a slow rate of change a vector and V/F may be very close in amp draw.

If you have an application where you need the vector for starting or stopping quickly but you are using a lot of current at speed you can change vector parameters to reduce the current. In some applications it is cheaper to oversize a V/F drive to get starting or stopping torque if you don't need precise speed control.
I accept the fact that, in the practice, V/f is considered by many the better choice for fan loads, but I see few reasons why V/f approach could result in better efficiency.

One reason could be that, since it doesn't try to regulate anything, practically it can't oscillate due to weak stability, although oscillations may still occur (I've seen a heavily vibrating torque measurement on a fan driven by a V/f variable frequency drive).
Another could be that, while non-linear V/f curves (suitable to non-linear loads as fans) are quite common, the same is not done for the flux reference (magnitude) in vector control.
And, of course, the few parameters of a V/f control are far easier to tune than a vector scheme (which companies don't really share).

However, one interesting thing that can be done with vector control is, for slow dynamics applications, to automatically tune the flux reference to achieve a minimum loss control during the control operation. I don't think this would be possible with V/f.

Post a Comment:

    
Calculate (1 - 2) =

You may also like:

As using soft starter could result in reducing torque of the motor. Soft starter normally reduces starting current by reducing starting voltage. However, decreasing voltage will lead to starting toque ...
Before you select kind of cable for your consumer, you need to calculate expected operating current of cable which depends from rated power of your consumer. After that, before you select kind of cable for ...
For now I am working on a mining project which involves starting two SAG mills, the method of starting these mills is by rotor resistance and likewise we are using an energy recovery system (SER), could ...
Humidity plays important part in flashover. We faced a problem of flashovers in Air insulated 11kV Switchgear busbar compartments in rainy seasons. Any sharp edge will ionize the surrounding air, which becomes ...
Paralleling IGBT modules where the IGBT but not the diode has a PTC is commonly done at higher powers. I personally have never done more than 3 x 600A modules in parallel but if you look at things like high ...
Gozuk Service Gozuk Blog: all about electric motor control & drives industries development in energy saving applications.

Featured

Like pumps, fans consume significant electrical energy while serving several applications. In many plants, the VFDs (variable ... energy consumedA frequency inverter controls AC motor speed. The frequency inverter converts the fixed supply frequency (60 Hz) to a ... Motor starter (also known as soft starter, motor soft starter) is a electronic device integrates soft start, soft stop, ... Soft starter allows the output voltage decreases gradually to achieve soft stop, in order to protect the equipment. Such as the ... Soft Starter reduces electric motor starting current to 2-4 times during motor start up, reduces the impact to power grid during ...

In Discussion