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6.1 SYMBOLS
6.2 INTRODUCTION
6.2.1 V/F (Scalar) Control
DETAILED PARAMETER DESCRIPTION
This chapter describes in detail all CFW-10 parameters and
functions.
Please find below some symbols used in this chapter:
AIx = Analog input number x.
AO = Analog output.
DIx = Digital input number x.
F* = Frequency reference. This is the frequency value that
indicates the desired motor speed at the inverter output.
F
= Input frequency of the acceleration and deceleration ramp.
e
F
= Maximum output frequency, defined at P134.
max
F
= Minimum output frequency, defined at P133.
min
F
= Output frequency - frequency applied to the motor.
s
I
= Rated inverter output current (rms), in Ampères (A). This
nom
value is defined in P295.
I
= Inverter output current.
s
I
= Active current at inverter output, i.e., it is the compoment
a
of the total motor current proportional to active electric power
absorbed by the motor.
RLx = Relay output number x.
U
= DC link voltage in the DC link circuit.
d
This section describes the main concepts related to the CFW-
10 frequency
inverter.
This control mode is based on the constant V/F curve(P202=0
- linear V/F curve). Its performance is limited at low frequencies
as function of the voltage drop in the stator resistance, that
causes a significant magnetic flow reduction in the motor air
gap and consequently reducing the motor torque. This
deficiency should be compensated by using manual and
automatic boost torque (IxR compensations), that are set
manually and depend on the user experience.
In most applications (for instance: centrifugal pumps and fans)
the setting of these functions is enough to obtain the required
performance. But there are applications that require a more
sophisticated control. In these cases it´s recommended the use
of the sensorless vector control, that will be described in the
section below.
In V/F control, the speed regulation, that can be obtained by
setting properly slip compensation can be maintained within
1 to 2% of the rated speed. For instance, for a IV pole motor/
60Hz, the minimum speed variation at no load condition and
at rated load can be maintained between 18 and 36rpm.
CHAPTER 6
49
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