KFU 2-/4-
112
11 Operational
Behavior
The operational behavior of the frequency inverter can be adjusted to the application
by setting the parameters appropriately. In particular the acceleration and decelera-
tion behavior can be selected according to the selected
Configuration
30
. Addition-
ally, features such as Auto Start, and the synchronization and positioning functions
facilitate the integration in the application.
11.1 Starting
Behavior
The start of the 3-phase machine can be parameterized in accordance with the con-
trol functions and methods. In contrast to the sensorless control method, the field-
oriented control methods only require the definition of the limit values
Maximum
flux
formation time
780
and
Current during flux formation
781
for the adjustment of the
acceleration behavior. The acceleration behavior of the sensorless control method in
configurations 110 and 111 can be selected as described in the following chapter.
11.1.1 Starting Behavior of Sensorless Control System
The parameter
Operation mode
620
for the starting behavior is available in configu-
rations 110 and 111. Depending on the operation mode selected, the machine is
magnetized first or a starting current is impressed. The voltage drop across the stator
resistance which reduces the torque in the lower frequency range can be compen-
sated by the IxR compensation.
To ensure the correct function of the IxR compensation, the stator resistance is de-
termined during the guided commissioning. The IxR compensation is only activated
when the stator resistance was determined correctly.
Operation mode
620
Starting Behavior
0 -
Off
At the start the voltage with the value of parameter
Starting Voltage
600
is set at an output frequency of
0 Hz. After this, the output voltage and the output fre-
quency are changed according to the control method.
The break-away torque and the current at the start are
determined by the adjusted starting voltage. It may be
necessary to optimize the starting behavior via the pa-
rameter
Starting voltage
600
.
1 -
Magnetization
In this operation mode, the
Current during flux-
formation
781
for magnetization is impressed into the
motor after release. The output frequency is kept at zero
Hz for the
Maximum flux-formation time
780
. After this
time has expired, the output frequency follows the ad-
justed V/f characteristic. (see operation mode 0- Off)
2 -
Magnetization and
current impression
Operation mode 2 includes operation mode 1. After the
Maximum flux-formation time
780
has elapsed, the out-
put frequency is increased according to the set accelera-
tion. If the output frequency reaches the value set with
the parameter
Frequency limit
624
, the
Starting current
623
is withdrawn. There is a smooth transition to 1.4
times the frequency limit to the set V/f characteristic. As
from this operating point, the output current depends on
the load.
3
-
Magneti
IxR compensation
Operation mode 3 includes operation mode 1 of the start
function. When the output frequency reaches the value
set with parameter
Frequency limit
624
, the increase of
the output voltage by the IxR compensation becomes
effective. The V/f characteristic is displaced by the por-
tion of voltage which depends on the stator resistance.
