WEG CFW500 V1.8X, Руководство по программированию, Страница: 77 / 172

V/f Scalar Control
CFW500 | 9-1
9
9 V/f SCALAR CONTROL
This is the classical control method for three-phase induction motors, based on a curve that relates output
frequency and voltage. The inverter works as a variable frequency and voltage source, generating a combination
of voltage and frequency according to the configured curve. It is possible to adjust this curve for standard 50 Hz,
60 Hz or special motors.
According to the block diagram of Figure 9.1 on page 9-2 , the speed reference f* is limited by P0133 and P0134
and applied to the input of “V/f CURVE” block, where the output voltage amplitude and frequency imposed to
the motor are obtained. For further details on the speed reference, refer to
Chapter 7 LOGICAL COMMAND AND
SPEED REFERENCE on page 7-1 .
By monitoring the total and active output current, and the DC link voltage, compensators and regulators are
implanted so as to help in the protection and performance of the V/f control. The operation and parameterization of
those blocks are detailed in
Section 11.2 DC LINK VOLTAGE AND OUTPUT CURRENT LIMITATION on page 11-3 .
The advantage of the V/f control is its simplicity and the need of few settings. The start-up is quick and simple,
normally requires little or no modification. Besides, in cases where the application allows the proper adjustments
of the V/f curve, you save energy.
The V/f or scalar control is recommended for the following cases:
„
Drive of several motors with the same inverter (multi-motor drive).
„
Energy saving in the drive of loads with quadratic torque/speed relationship.
„
Motor rated current lower than 1/3 of the inverter rated current.
„
For test purposes, the inverter is turned on without motor or with a small motor with no load.
„
Applications where the load connected to the inverter is not a three-phase induction motor.