Description of the Software Modules and Parameters
Parameter manual b maXX BM3000
Document no.: 5.12001.07
499
of 820
4
Thereby the complete control of and the current DC link voltage are considered to calcu-
late U
ph,Max
. This is the reason that at instantaneous reductions of the DC link voltage the
voltage limit and the torque current limit drops.
A limit speed n
E
, is implemented that limits the speed-dependent torque current limit
stronger than the set max. torque current
Z19.8– I
q,Max
limits the torque current.
The resulting voltage phasor is I
q,set
= l
q,Max
and n
act
= n
E
and therefore forms an angle
of 45° (assuming the Usq voltage of the field weakening is reduced to (1/
2) * U
ph,Max
).
If this angle is reached by the increase of the lq current there is no increase of the torque
at the asynchronous machine anymore and therefore must be limited.
Factor of breakdown torque
Additionally, the operating speed still can be adjusted by the parameter Z138.17– (factor
at the breakdown torque S
k
). The smaller the factor the smaller the Ud voltage limit and
the greater the distance to the breakdown torque.
At the ASM S
k
may not be greater than 1. At the SM S
k
may be set >1 (but 2). This
way more torque current can be applied but the distance to the breakdown torque is re
-
duced.
The resulting speed-dependent torque current limit of the entered breakdown torque fac-
tor is displayed in parameter Z138.18– "Isq limit breakdown torque". The resulting limit
speed is displayed in "Breakdown torque limit" (Z138.16–).
The available phase voltage
The existent voltage, U
ph,Max
dependent of the field weakening controller mode is deter-
mined as follows:
m Field weakening at the voltage limit
u
max
, Maximum output voltage RMS, Z142.6–
u
lim
, Voltage threshold for field weakening, Z142.8–
m Permanent field weakening
u
max
, Maximum output voltage RMS, Z142.6–
n
E
60
el
2 p
--------------
60 U
d,Max
2 pL
q
I
qMax
--------------------------------------------==
U
d.Max
S
k
1
2
-------
U
ph,Max
=
U
ph,Max
1
3
-------
min u
max,
u
lim
=
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