I am in the maintenance department of a production company. We had some problem with a motor drive. The drive was rated 250 Kw and was using vector control mode for its operation.

I want to know that what is the difference between a vector control drive and a variable frequency drive ???

 

Sensorless... I suggest you search the Control.Com Archives.

Regards, Phil Corso

 

Closed loop vector or full vector uses an encoder to read motor angle so the drive can more accurately produce the proper waveform. This provides good performance at most speeds including zero speed. Open loop vector uses a mathematical model and possibly current feedback to calulate motor position. Open loop vector is pretty good until the motor is near zero speed, then it can lose control somewhat. Variable freq just puts out a waveform and hopes that the motor is following.

The two vector modes provide good speed control with varying loads because the output waveform is synchronized with the motor. A VFD usually has the motor running a few percent slower than the output waveform, depending on load.

Bill Sturm

 

"uses an encoder to read motor angle"

that statement is a little misleading... technically it is only looking for the velocity of the motor. some use an encoder, there are a few models that allow a tach. vector drives don't care about position or angle.