Baumuller b maXX BM2500, Руководство по эксплуатации

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Monitoring
Parameter manual b maXX BM3000
Document no.: 5.12001.07 Baumüller Nürnberg GmbH
738
of 820
4.11
Derating characteristic of asynchronous machines without forced ventilation
Standard asynchronous machines without forced ventilation normally require a derating
of the maximum continuous current at speeds lower than the rated speed.
Figure 233: Typical derating of standard asynchronous machines (without forced ventilation)
Two derating factors are provided which proportionally to the rated speed lower the max-
imum continuous current at the standstill point and at half the rated speed. Based on this
a current limit curve is interpolated from the available current values again and is used for
the calculation of the l
2
t actual value (see
Z
Fig. 233
–
). The maximum continuous current
is fixed to the rated current if it is above the rated speed.
Figure 234: Speed-dependent l
2
t overload monitoring of asynchronous machines without forced ventilation
4.11.5.3 Monitoring of the single phases
The standardized solution referring to the monitoring of the complete current is insufficient
for many applications at low speeds and in standstill. Therefore an implementation solu-
tion is presented which considers the output frequency effect lower than the thermal time
constant of the motor.
During slow motion the 3 phases are unequally loaded. By l
2
t monitoring mode
Z
6.43
–
bit 3 to 1 instead of the l
2
values of the apparent current the l
2
values can be evaluated
separately for every phase (
Z
47.32
–
to
Z
47.34
–
). The "Motor l
2
t actual value"
Z
6.28
–
25 50 75 100 125 150
20
40
80
100
60
6.46[1]
6.46[0]
5000_0361_rev01.cdr
Df
%
Motor speed / Nominal speed, %
(Self ventilated)
N
D
N
D
N
1
N
6.46[0]
6.46[1]
6.46[0], 6.46[1]
18.22
5000_0362_rev01.cdr
Ref
I
107.9
Df
Motor I t derating factors
2
Speed actual value
Nominal current
I´act
I values
2