WEG CFW-11 Programming Manual page 227

Example: For a motor with the following characteristics,
I = 10.8 A
n
T = 4 s (hot motor blocked rotor time)
BR
= 7.8 ⇒ I
I / I = 7.8 x 10.8 A= 84.2 A
p n p
SF = 1.15
one gets,
Overload Current =
I x SF
n
Overload Time = T = 4 s
BR
After this, it is only necessary to plot the calculated values on the motor overload graph (
the thermal class curve immediately below the calculated point.
Overload Time
100000
10000
1000
100
10
1
0
I 84.2
p
= x 100 = 678 %
10.8 x 1.15
1 2 3 4 5
1x 2x 3x 4x 5x 6x
(a) - Cold motor overload curves for loads of the HD and ND types
Class 45
Class 40
Class 35
Class 30
Class 25
Class 20
Class 15
Class 10
Class 5
Current x In for F.S. = 1.00
6 7 8 9 10
Current x In for F.S. = 1.15
7x 8x 9x 10x
Faults and Alarms
on page 15-7, and to select
15-7
15