4
Settings Calculation
SIMPRO-100
52 PRIM-2400C
By examining the curve, we can find the thermal
limit times at various multiples of Full Load
Current, as listed in Table 4.11. These times map
directly to the relay settings shown below the
table.
Table 4.11 3000 HP Motor Thermal Limit Times
Phase current transformers having 500:5 ratios
are selected for the application. The
SIMPRO-100 Relay settings for the application
are calculated as shown below.
Current Transformer Ratio (CTR) =
00/5 = 100
CT Secondary Rating (ITAP) = 5
Full Load Amps (FLA) =
366/100 = 3.66 A secondary
Service Factor (SF) = 1.25
Time to Trip at 1.30 x FLA (TTT130) = NP
Time to Trip at 1.40 x FLA (TTT140) = NP
Time to Trip at 1.50 x FLA (TTT150) = NP
Time to Trip at 1.75 x FLA (TTT175) =
625.0 seconds
Time to Trip at 2.00 x FLA (TTT200) =
400.0 seconds
Time to Trip at 2.25 x FLA (TTT225) = NP
Time to Trip at 2.50 x FLA (TTT250) =
225.0 seconds
Time to Trip at 2.75 x FLA (TTT275) = NP
Time to Trip at 3.00 x FLA (TTT300) = NP
Time to Trip at 3.50 x FLA (TTT350) = NP
Time to Trip at 4.00 x FLA (TTT400) =
72.0 seconds
Time to Trip at 4.50 x FLA (TTT450) =
58.0 seconds
Time to Trip at 5.00 x FLA (TTT500) =
30.0 seconds
Time to Trip at 5.50 x FLA (TTT550) =
25.0 seconds
Time to Trip at 6.00 x FLA (TTT600) =
18.1 seconds
Time to Trip at 6.50 x FLA (TTT650) =
15.2 seconds
Time to Trip at 7.00 x FLA (TTT700) =
13.2 seconds
Time to Trip at 7.50 x FLA (TTT750) = NP
Time to Trip at 8.00 x FLA (TTT800) = NP
Time to Trip at 8.50 x FLA (TTT850) = NP
Time to Trip at 9.00 x FLA (TTT900) = NP
Time to Trip at 10.00 x FLA (TTT1000) = NP
The relay neither requests settings for thermal
limit times less than the service factor nor does it
require that all settings have a time entered. You
can enter NP for some points and the relay
automatically builds the thermal limit curve
between the nearest two specified points. For
instance, the relay thermal limit characteristic
between 2.5 and 4.0 times Full Load Amps forms
a continuous curve between 225 seconds and
72 seconds.
Multiples of Full
Load Current
Thermal Limit
Time (Sec)
1.75 625
2.00 400
2.50 225
4.00 72
4.50 58
5.00 30
5.50 25
6.00 18.1
6.50 15.2
7.00 13.2
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