Parameterization Of The V/F Scalar Control - WEG CFW501 V1.8X Programming Manual

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 P0202 allows the selection of other options for the control mode,
as per chapter 8 AVAILABLE MOTOR CONTROL TYPES on page
The V/f curve is completely adjustable in five different points as shown in
although the factory default
defines a preset curve for motors (1500 rpm / 50 Hz) ou (1800 rpm / 60 Hz), as per options of P0204. In this
format, point P0 defines the amplitude applied at 0 rpm, while P3 defines the rated amplitude and frequency
and beginning of field weakening. Intermediate points P1 and P2 allow the setting of the curve for a non-linear
relationship between torque and speed, for instance, in fans where the load torque is quadratic in relation to the
speed. The field weakening region is determined between P
Output
voltage (%)
P0142
P0143
P0144
P0136
The CFW501 factory default settings define a linear relationship of the torque with the speed, overlapping points
P1, P2 and P3 at 1500 rpm (50 Hz) or 1800 rpm (60 Hz); refer to the description of P0204. In this way, V/f curve is a
straight line defined by just two points, P0136 which is the constant term or voltage in 0 Hz and the rated frequency
and voltage operation point 1500 rpm (50 Hz) or 1800 rpm (60 Hz) and 100 % of maximum output voltage).
The points P [P0136, 0 Hz], P
0
adjusted so that the voltage and frequency relationship 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 speed, such as in centrifugal
pumps and fans, the points of the curve can be adjusted so energy saving is obtained.
NOTE!
A V/f quadratic curve can be approximated by: P0136 = 0; P0144 = 11.1 % and P0143 = 44.4 %.
NOTE!
If P0147 ≥ P0146 or P0146 ≥ P0145 or the V/f curve results in a segment with slope (rate) above
10 % / Hz, CONFIG (CONF) status is activated.
NOTE!
In frequencies below 0.1 Hz, the output PWM pulses are cut, except when the inverter is in DC braking.
P
2
P
1
P
0
P0147 P0146
Figure 9.2: Curve V/f
[P0144, P0147], P [P0143, P0146], P
1 2
8-1.
Figure 9.2: Curve V/f on page
and P , where the amplitude is maintained in 100 %.
3 4
P P
3 4
Output
P0145 P0134
frequency (Hz)
[P0142, P0145] and P
3
V/f Scalar Control
9-3,
[100 %, P0134] can be
4
CFW501 | 9-3
9