WEG CFW300 V1.3X, Programming Manual

Page: 65 / 157

V/f Scalar Control
CFW300 | 9-3
9
9.1 PARAMETERIZATION OF THE V/f SCALAR CONTROL
The scalar control is the inverter factory default control mode for its popularity and because it meets most
applications of the market. However, parameter P202 allows the selection of other options for the control mode,
as per
Chapter 8 AVAILABLE MOTOR CONTROL TYPES on page 8-1 .
The V/f curve is completely adjustable in four different points as shown in Figure 9.2 on page 9-3 , although the
factory default set a curve pre-adjusted for motors 50 Hz or 60 Hz, as options for P204. This format, point P0
defines the amplitude applied at 0 Hz, while P2 defines the rated amplitude and frequency and beginning of field
weakening. Intermediate points P1 allow the setting of the curve for a non-linear relationship between torque and
frequency, for instance, in fans where the load torque is quadratic in relation to the frequency. The field weakening
region is determined between P2 and P3, where the amplitude is maintained in 100 %.
P134 P145 P146
P
0
P
1
P
2
P
3
P142
P143
P136
Output
frequency (Hz)
Output
voltage (%)
Figure 9.2: Curve V/f
The factory default setting of the CFW300 defines a linear relation of the torque with the frequency by means of
three points (P
0
, P
1
and P
2
).
The points P
0
[P136, 0 Hz], P
1
[P143, P146], P
2
[P142, P145] and P
3
[100 %, P134] can be set so that the voltage and
frequency relation imposed to the output approximates the ideal curve for the load. Therefore, for loads in which
the torque behavior is quadratic in relation to the frequency, such as in centrifugal pumps and fans, the points
of the curve can be set or the Quadratic V/f control mode can be used so as to save energy. This Quadratic V/f
curve is presented in
Figure 9.3 on page 9-3 .
P134 P145
P142
P136
Output
frequency (Hz)
Output
voltage (%)
Figure 9.3: Quadratic V/f Curve
NOTE!
In frequencies below 0.1 Hz, the output PWM pulses are cut, except when the inverter is in DC
Braking mode.