Baumuller b maXX BM5800 - Page 722

Monitoring
Parameter manual b maXX BM5800
Document No.: 5.16029.03 Baumüller Nürnberg GmbH
722
of 814
3.11
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 192: 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 ZFig. 192–). The maximum continuous current
is fixed to the rated current if it is above the rated speed.
Figure 193: Speed-dependent l
2
t overload monitoring of asynchronous machines without forced ventilation
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