Example Of Trip Class Selection; Example For The Trip Class Selection For A Given Motor - ABB UMC100.3 Manual

C O N F I G U R I N G T H E M OTO R P R OT E C T I O N F U N C T I O N S

Example of trip class selection:

Select the trip class so that the motor is thermally protected, even when the rotor is stalled. This means that the tripping curve of a
cold motor has to be below the coordination point Ia/Ie and tE whereas Ia is the actual current, Ie is the nominal current of the mo-
tor and tE is the maximal heating time as defined by the motor manufacturer. Example: Motor with enhanced safety has the data:
• Power = 7.5 kW
• Relation I /I = 7.4
a e
• Heating time t = 11 s
E
The following diagram shows the tripping time for cold motors at symmetric load:
10000
1000
100
t =11s
10
E
1
1 1,5 2 2,5
—

Example for the trip class selection for a given motor

The trip classes 5 and 10 are allowed because the appropriate times (3 s, 7 s) are below the time tE of the motor
(including the tolerance 10% of the UMC).
3 3,5 4 4,5 5 5,5 6
I / Ie
6,5 7 7,5 8 8,5 9 9,5 10
I /I =7,4
a e
Class 40E
Class 30E
Class 20E
Class 10E
Class 5E
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