User`s guide

CHAPTER 6 - DETAILED PARAMETER DESCRIPTION

6.2.3

Vector Control (VVC)

In V/F control, the speed regulation, that can be obtained by

setting properly slip compensation can be maintained within

1 % to 2 % of the rated speed. For instance, for a IV pole

motor/60Hz,the minimum speedvariation at no load condition

and at rated load can be maintained between 18 and 36 rpm.

Thereis still a variation of the linear V/F control: the quadratic

V/F control. This control mode is suitable for applications like

centrifugal pumps and fans (loads with quadratic torque x

speed characteristics),since it enablesa motor lossreduction,

resulting in an additional energy saving by using an inverter.

For more details about the V/F control mode, please refer to

the description of the parameters P136, P137, P138, P142

and P145.

In the sensorless vector control available at the CFW-08, the

inverter operation is optimized for the used motor, so that a

better performance in terms of torque and speed regulation

is obtained. This vector control does not require a signal of

the speed feedback through tachogenerator or encoder

coupled on motor shaft.

To maintain the magnetic flux in the motor air gap constant,

and consequently the motor torque, within the whole speed

variation range (from zero up to the field weakening point), a

sophisticated control algorithm is used that considers the

mathematic model of the induction motor.

Thus one can maintain the magnetic flux in the motor air gap

approximatelyconstant at frequenciesdown to approximately

1 Hz.

In vector control mode one can obtain a speed regulation of

0.5% (relating to the rated speed).Thus, for instance, for a IV

pole motor/60 Hz one can obtain a speed variation in the ran-

ge of 10 rpm.

Other advantage of the vector control is its easy setting

procedure. The user needs only to enter in the parameters

P399 and P407 the information about the used motor

(nameplate data) and runs the self-tuning routine (by setting

P408 = 1) and the inverter configures itself to the required

application. So the inverter is ready to be operated in an

optimized manner.

For more information,refer tothe descriptionofthe parameters

P178 and P399 to P409.