ABB UMC100-FBP - Page 40

- 40 -UMC100-FBP
Universal Motor Controller
UMC100-FBP
Technical Description
FieldBusPlug / Issue: 03.2012
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 I
a
/I
e
and t
E
whereas I
a
is the actual current, I
e
is the nominal current of the motor and t
E
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
a
/I
e
= 7.4
•Heating time t
E
= 11 s
The following diagram shows the tripping time for cold motors at 3-pole symmetric load:
 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 t
E
of the
motor (including the tolerance 10% of the UMC).
1
10
100
1000
10000
1 1,5 2 2,5 3 3,5 4 4,5 5 5,5 6 6,5 7 7,5 8 8,5 9 9,5 10
I / Ie
tripping time [s]
Class 40E
Class 30E
Class 20E
Class 10E
Class 5E
I
a
/I
e
=7,4
t
E
=11s