6.1.9.4 High Motor Load
The switching frequency is adjusted automatically according to the motor current. When a certain percentage of the nominal HO
motor load is reached, the switching frequency is derated. This percentage is individual for each frame size and a value that is coded
in the EEPROM along with the other points that limit the derating.
Illustration 26: Derating of switching frequency according to motor load. f1, f2, I1, and I2 are coded in EEPROM.
In EEPROM, the limits depend on the modulation mode. In 60° AVM, f1 and f2 are higher than for SFAVM. I1 and I2 are independent
of the modulation mode.
6.1.9.5 High Voltage on the DC link
The switching frequency is adjusted automatically according to the voltage on the DC link. When the DC link reaches a certain mag-
nitude, the switching frequency is derated. The points that limit the derating are individual for each frame size and are coded in the
EEPROM.
f2
U1 U2
U
dc
[V]
e30bb978.10
Illustration 27: Derating of switching frequency according to voltage on the DC link. f1, f2, U1, and U2 are coded in EEPROM.
In EEPROM, the limits depend on the modulation mode. In 60° AVM, f1 and f2 are higher than for SFAVM. U1 and U2 are independ-
ent of the modulation mode.
6.1.9.6 Low Motor Speed
The selection of PWM strategy depends on the stator frequency. To prevent that the same IGBT is running for too long (thermal
consideration), f
m,switch1
is specied as the minimum stator frequency for 60° PWM. f
m,switch2
is specied as the maximum stator fre-
quency for SFAVM to protect the drive. 60° PWM helps to reduce the inverter loss above f
m,switch1
as the switch loss is reduced by 1/3
by changing from SFAVM to 60° AVM.
e30bb979.11
PWM
SFAVM
60 PWM
f
m,switch 1
f
m,switch2
f
m
[Hz]
Within this area, both
strategies can be used.
Illustration 28: Selection of PWM Strategy
AJ300847815559en-000101 / 130R033742 | Danfoss A/S © 2020.09
Product Features
VLT® AQUA Drive FC 202
Design Guide
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