Monitoring
Parameter manual b maXX BM5800
Document No.: 5.16029.03 Baumüller Nürnberg GmbH
714
of 814
3.11
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.
m not until after 30 s the calculated temperature is below the threshold
SemLimRed
and,
m if there is no current limit existent.
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 Z130.15– is set to 2 kHz or if the precondition "Current cycle <
RT0" wasn't considered during the reduction, PWM reduction cannot be processed.
3.11.4 Temperature monitoring of the motor
Three different encoder types can be utilized:
m KTY84/130 (PTC with an almost linear characteristic for precise evaluation of the tem-
perature)
m Temperature switch (motor protection thermistor (PTC) conforming to DIN 44080-082)
m PT1000 (PTC with linear characteristic)
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
temperature model
Z175.1– must be set). Furthermore, the drive components
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).
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