Scalar Control (V/F) - WEG CFW-11 Programming Manual

It consists of a simple control based on a curve that links output voltage and frequency. The inverter operates
as a voltage source, generating frequency and voltage values according to that curve. It is possible to adjust
this curve to standard 50 Hz or 60 Hz motors or to special ones through the adjustable V/f curve. Refer to the
block diagram at the figure 9.1.
The advantage of the V/f control is that due to its simplicity just a few settings are necessary. The start-up is fast
and simple, and the factory settings require generally few or no modifications.
P0202=Type of Control
P0202=0 or 1=V/f
V
P0136
Total Reference
(Refer to figure 13.8)
V P0202=2=Adjustable V/f
P0142
P0143
P0144
V
V
P0137
Automatic Torque
BOOST
The V/f or scalar control is recommended for the following cases:
 Operation of several motors with the same inverter (multimotor operation);
 The motor rated current is less than 1/3 of the inverter rated current;
 The inverter is, for test purposes, enabled without motor or with a small motor and no load.
The scalar control can also be used in applications that do neither require fast dynamic response, nor accuracy
in the speed regulation, and also do not require high starting torque (the speed error is a function of the motor
slip, and by programming the parameter P0138 – Slip Compensation – it is possible to get a accuracy of
approximately 1 % at the rated speed with the load variation).
Speed
P0146 P0145
Speed
Reference
V
P0138
Slip Compensation
Speed
Speed
Figure 9.1 - V/f control block diagram

Scalar Control (V/f)

ScaLaR coNtRoL (V/f)
PWM
PWM
V
f
I = Output Current
s
tRaNSf.
I active
P0139
9
9-1