ABB ACS800 User Manual page 42

42
In practice, the voltage boost is achieved through IR compensation. In the example,
the parameter 26.03 IR COMPENSATION should be set to 6%
(0.06 × 690 V = 41.4 V). IR compensation should start at approximately slip
frequency in order to avoid transformer saturation. This can be achieved using
parameter 26.04 IR STEP-UP FREQ.
To summarise the above,
• the voltage boost value is a specification for the manufacturer of the transformer.
It defines how much the transformer is able to withstand overvoltage. The boost is
scaled according to the U/F curve
• voltage boost is implemented using IR compensation, which is scaled according
to the output voltage of the drive (690, 500 or 400 V).
Set parameter 26.03 IR COMPENSATION to the correct value (see the calculation
above). Note that BOOST and IR compensation have different scalings. If the value
is not known, use values starting from 0.5% (of nominal motor voltage).
Set parameter 26.04 IR STEP-UP FREQ to approximately
where
Note: Instead of using the motor rating plate data, set parameter 99.05 MOTOR
NOM VOLTAGE according to the nominal supply voltage of the drive (e.g. 690 V).
Set parameter 99.06 MOTOR NOM CURRENT to
where U1 and U2 are the primary and secondary voltages of the step-up transformer
respectively.
Appendix – Step-up applications
n – n
s n
⋅
--------------- - f
n
n
s
⋅ ⋅
60 f 2
n
--------------------------- -
n =
s
polenumber
U
2
⋅
------ I
n
U
1
n = nominal motor speed in rpm
n