67
DETAILED PARAMETER DESCRIPTION
There is 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 enables
a motor loss reduction, 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.
Inverter performance improvements can be achieved when the sensorless
vector control is selected (P202=2).
The CFW-08 vector control is sensorless, i.e., it does not require a signal
of the speed feedback through tachogenerator or encoder coupled on
motor shaft.
To maintain the magnetic flow 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 mangetic flow in the motor air gap approximately
constant at frequencies down to approximately 1 Hz.
In vector control mode one can obtain a speed regulations about 0.5%
(relating to the rated speed). Thus, for instance, for a IV pole motor/60Hz
one can obtain a speed variation in the range of 10rpm (!).
Other advantage of the vector control is its easy setting procedure.
The user needs only to enter in the parameters P399 and 407 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 optmized manner.
For more information, refer to the description of the following parameters:
P178 and P399 to P409.
The frequency reference (i.e., the desired output frequency, or alternatively,
the motor speed) can be defined in several ways:
the keypad - digital reference that can be changed through the keypad
(HMI), by using the keys and (see P221, P222 and
P121);
analog input - the analog input AI1 (XC1:6) or the AI2 (XC1:8) can be
used, or both (see P221, P222 and P234 to P240);
multispeed - up to 8 preset digital references (see P221, P222 and
P124 to P131);
electronic potentiometer (EP) - another digital reference, its value
is defined by using 2 digital inputs (DI3 and DI4) - see P221, P222,
P265 and 266;
via serial.
Figure 6.1 shows through a diagram block the frequency reference definition
to be used by the inverter.
The block diagram in Figure 6.2 shows the inverter control.
6.2.3 Vector Control (VVC)
6.2.4 Frequency Reference
Sources
To Next Page
Loading...
Need help?
General
