WEG SSW-07 Manual Del Usuario página 45

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Chapter 5 - prOGraMMING INFOrMatION aND SUGGeStIONS
44
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t(s)
20 s
0
Figure 5.10 - Checking the minimum class of curves in cold condition
Therefore the minimum class necessary to start the cold motor is
Class 10. Class 5 will trip during starting.
NOTE!
If the motor must start in the hot condition, class 10 will trip during
the second start. In the case a higher thermal class must be set.
Determine the maximum thermal class:
To correctly program the Thermal Class that will protect your motor it
is essential to have in hand the motor locked rotor current and locked
rotor time. This information is available in the motor manufacturer's
catalogue. Put these values into figure 4.8, in case of the cold stall
time or into figure 4.9, in case of hot stall time.
For example:
Stall Current = 6,6 x ln
Hot Stall Time = 6s
t(s)
6 s
0
Figure 5.11 - Checking the maximum class of curves in hot condition
Class 25 is the highest class that protects the motor.
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Cold
F.S.=1
2.5 x ln of the
motor
6.6 x ln of the
motor
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15
10
5
xln
Hot
30
25
20
xln
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