Lenze i950 Series, Manual

Page: 245 / 500

13.4.5 Set voltage boost
As an alternative for the " Activate voltage vector control (Imin controller) " function, a con-
stant, load independent voltage boost can be specified for low speeds (below the V/f rated
frequency) or for a motor standstill in order to optimise the starting performance.
WARNING!
Insufficient cooling of the motor due to longer operation at standstill.
If the motor is operated at standstill for a longer time - especially in case of smaller motors -
the motor can be destroyed by overtemperature!
▶
Connect the PTC thermistor (single sensor according to DIN 44081 or triple sensor according
to DIN 44082) or thermal contact (normally-closed contact)
4
Motor temperature monitor-
ing .
^
296
▶
Parameterise and activate the
4
Motor overload monitoring (i²*t) .
^
288
NOTICE
The voltage boost is added to the function
4
Activate voltage vector control (Imin control-
ler) .
^
243
Only set one of the two "boost" functions.
Recommendation: voltage vector control
For magnetising the motor, consider a sufficient time from the controller enable
to the start of the speed ramp function generator. The bigger the motor the lon-
ger the time required for magnetisation. A motor with a power of 90 kW
requires up to 2 seconds.
Depending on the required starting torque, the voltage boost must be set so that the required
motor current will be available after controller enable.
•
The voltage boost can be calculated by multiplying the stator resistance by the rated mag-
netising current:
= ´
Anlaufstrom ~ U R I
Boost s mN
0
0
U
Boost
0
0
U
Boost
Frequenz im Eckpunkt
Spannung im Eckpunkt Spannung im Eckpunkt
Frequenz im Eckpunkt
U
U
Boost
f
soll
U U
f
soll
U
0
0
0
0
•
Optionally, the voltage boost can be determined empirically by increasing the setting until
the rated magnetising current flows.
•
The voltage boost is added geometrically to the voltage of the characteristic:
2 2
Kennlinie Boost
U= U U
+
Parameter
Address Name / setting range / [default setting] Info
0x2B06 Voltage boost
0.0 ... [0.0] ... 100.0 V Setting of the voltage boost for the voltage vector control.
Configuring the motor control
V/f characteristic control for asynchronous motor (VFC open loop)
Set voltage boost
245