Motor Protection By I2T- Monitoring - BONFIGLIOLI ACTIVE Cube ACU 201-01 Operating Instructions Manual

In calculation the tripping time the measured output current in operating points below
the frequency limit is evaluated by a factor between 1 and 2.
factor is a function of the stator frequency. The increased thermal load of self-
ventilated motors in the lower speed range is therefore considered.
The table shows in extracts factors for motor rated frequency 50Hz.
300%
0 200%
5 188%
10 177%
20 160%
30 147%
50 129%
100 106%
150 100%

18.5.2 Motor Protection by I2t- Monitoring

To protect the motor against overload the I2t monitoring provides a further possibility
for the user.
This kind of motor protection is mainly used in servo technology. When using servo
motors the I2t- monitoring is a proven alternative to motor protection switch.
By integrating temperature-dependent parameters, measurable or known, the heat-
ing of a mathematical model is simulated.
The kind of the I
This parameter is switchable via data set.
The I²t monitoring works by function (I
The monitored value is evaluated via a PT1 element with the thermal time constant of
the stator.
If the output of PT1 element is bigger than 120%, then an error message is generat-
ed and the drive switches off. The threshold of 120% prevents, that an overshoot
leads to an immediate shutdown.
In the application should be avoided exceeding 100% capacity of the stator winding
permanently.
248
Frequency limit 572
100%
200% 150%
200%
200% 200%
168%
182% 177%
168% 160% 147%
147% 137% 122%
109%
132% 122%
100%
114% 106%
100% 100% 100%
100% 100% 100%
2
t monitoring mode can be selected by
Operating Instructions ACU
The determination of this
80% 60% 40%
200% 200% 200%
162% 153% 139%
139% 129% 114%
114% 106% 100%
103% 100% 100%
100% 100% 100%
100% 100% 100%
100% 100% 100%
Operation Mode
/I )² as shown in the figure.
act n
20% 10%
200% 200%
114% 100%
100% 100%
100% 100%
100% 100%
100% 100%
100% 100%
100% 100%
571.
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