Real Power Limit - Baumuller b maXX BM3000 Operating Manual

4.11
Monitoring
The instantaneous (operating) PWM frequency is displayed in parameter Z130.41–. At
the same time the corresponding instantaneous (operating) cycle time of current control-
ler is displayed in parameter Z47.65–.
In some circumstances the switching frequency reduction isn't enough, to avoid a current
limit.
If PWM reduction was activated, the device returns to the PWM frequency Z130.15–,
which was set.
The 30 s time slice is an empirical value, which is great enough so that all devices can
recover thermally.
In general, the PWM reduction is not active. It may be enabled in Bit 0 of the PU tempera-
ture model mode Z175.1–. It can be enabled in the inhibited drive status, only.
PWM-reduction is subject to the same limitations as at switchover to the set PWM-fre-
quency during the continuous operation (see Z130.15–). They are available for the oper-
ating modes speed control and current control - they aren't available for SM sensorless.
The failures in the controller were minimized during the implementation of the PWM
changes in the continuous operation. However, they cannot be excluded. Therefore, this
option is applicable to simple (not critical) applications, where the drive tolerates possible
failures.
If the PWM frequency
RT0" wasn't considered during the reduction, PWM reduction cannot be processed.

4.11.3.3 Real power limit

The real power limit is limited at the single-phase devices because otherwise the operat-
ing time cannot be guaranteed anymore as the Elko current is too high. This limit is active
only if the current is supplied by the system as well.
The real power limit is filtered by a PT
load is displayed on a percentage basis by the parameter Z6.47–. If this value rises to
more than 90% then the warning 221 is generated - if it rises to over 100% error 222 is
generated. The warning will be cleared again if the load drops to under 85%.
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m not until after 30 s the calculated temperature is below the threshold
and,
m if there is no current limit existent.
Z130.15–
NOTE!
m The user must assure that the drive with the reduced switching frequency can op-
erate correctly (e. g. check rated motor data, control quality at the reduced current
controller-bandwidth etc.) before the PWM reduction is enabled. (Bit 0 of the PU
Z175.1–
temperature model
must be checked, if they tolerate the reduced switching frequency (e.g. check mo-
tor filter if existing). This is particularly important, if PWM frequency was reduced
to 2 kHz.
m At the PWM reduction must be considered that the adjusting range of the output
frequency is reduced. The adjusting range is reduced from 450 Hz to 225 Hz if a
switchover from 4 kHz to 2 kHz is made (see chapter "Technical Data" in the in-
struction handbook of the device).
is set to 2 kHz or if the precondition "Current cycle <
must be set). Furthermore, the drive components
filter and a time constant of one second and the
1
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Sem LimRed
Baumüller Nürnberg GmbH