Description of the Software Modules and Parameters
Parameter manual b maXX BM5800
Document No.: 5.16029.03
457
of 814
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3.7.3.3 Torque Current Limiting
Axis units:
The torque current limiting acts on the integral term of the speed controller and on the out-
put of the motor manager before the current is forwarded to the current controller.
There is no limiting at the output of the speed controller because a digital filter can be in-
serted between the speed controller and the motor manager, or an Isq can additionally
be fed into the motor manager.
The torque current limiting can be set separately for motor or generator operation
(
Z138.2–, Z138.3–). By adapting the "Mode of Iq limit " Z138.1– bit 0, the separate lim-
iting can alternatively be applied to Torque Direction 1 or Torque Direction 2. For "asym-
metric" limiting, operating quadrants 1 to 4 are evaluated using the present speed and
torque current. Hysteresis
Z138.4– can be set when determining the operating quad-
rants.
Two symmetrical limits Z138.14– and Z138.15– are available in addition to the limit de-
pendent on quadrants. The limiting Z138.14– is intended for a fast cyclic access via anal-
ogous input or fieldbus process data. Other limits of the torque current are the breakdown
limit (
Z138.18–, also refer to ZBreakdown torque– on page 488), the derating of the peak
current devices (Z138.32–, also refer to ZPower unit– from page 61) or external limits
(refer to Z138.8–).
A torque current limit is set by the torque limit Z138.22– as well.
Other torque current limits are available Z138.18–, Z138.30–, Z114.5– and Z114.5–.
Furthermore, the torque current can be disabled due to a power failure (refer to Z130.10–
bit 1).
Always the less value of these limits is effective! The effective limit values are displayed
in
Z138.6– Iq upper limit and Z138.7– Iq lower limit.
The settable torque current limits Z138.2–, Z138.3–, Z138.14– and Z138.15– were
standardized by the "Max. torque current" Z19.8–. The reference value could change due
to field weakening or to external total current limit. Refer to the parameter Z19.8– and
Z138.1–.
Standardization modes of the torque current
Dependent of the standardization modes (parameter "Mode lq limit" Z138.1– bit 1 and
bit 3) the calculation of the parameter Z19.8– can be changed. Consequently, the follow-
ing standardization or limit modes accordant to the motor type are available: Load mode
Standard, Load mode ASM-lsdMax and the current mode.
At the load modes the parameter Z19.8– shows the possible torque current in depen-
dence of the available total current Z19.6– by subtracting the field current. Consequently
the ASM is available of more torque current while having the same total current and an
increased field weakening (less field current).
In contrast less torque current is available to the SM in the field weakening as in the basic
speed range.
Independently of the motor type the available torque current reduces if the total current of
the device is reduced (e.g. because overload monitoring has responded).
The Z19.8– standardized torque current limits are a part of the possible torque current
and therefore load limits. The ampere value of these limits will change at field weakening
and external total current limit.
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