M12352-1 v15
Table 54. Thermal overload protection, one time constant LCPTTR/LFPTTR
Function
Range or value
Accuracy
Reference current
(2-400)% of IBase
±1.0% of I
r
Reference temperature
(0-300)°C, (0 - 600)°F
±
1.0°C, ±2.0°F
Operate time:
2
2
2
2
ln
p
Trip
Amb
ref
ref
I
I
t
T
T
I
I
T
σ
,
<
,
,
√
EQUATION13000039 V3 EN-US
(Equation 1)
T
Trip
= set operate temperature
T
Amb
= ambient temperature
T
ref
= temperature rise above ambient at I
ref
I
ref
= reference load current
I = actual measured current
I
p
= load current before overload occurs
Time constant
t
= (1–1000)
minutes
IEC 60255-149, ±5.0% or ±200 ms whichever is greater
Alarm temperature
(0-200)°C, (0-400)°F
±2.0°C, ±4.0°F
Operate temperature
(0-300)°C, (0-600)°F
±2.0°C, ±4.0°F
Reset level temperature
(0-300)°C, (0-600)°F
±2.0°C, ±4.0°F
M13266-2 v9
Table 55. Thermal overload protection, two time constants TRPTTR
Function
Range or value
Accuracy
Base current 1 and 2
(30–250)% of
IBase
±1.0% of I
r
Operate time:
2
2
2
2
p
Trip
I
I
t
ln
I
I
σ
∑
⌡
,
< √
,
EQUATION1356 V3 EN-US
(Equation 2)
I = actual measured current
Ip = load current before
overload occurs
ITrip = steady state operate
current level in % of
IBasex
Time constant τ = (0.10–
500.00) minutes
±5.0% or ±200 ms whichever is greater
Alarm level 1 and 2
(50–99)% of heat content
operate value
±2.0% of heat content trip
Operate current
(50–250)% of
IBase
±1.0% of I
r
Reset level temperature
(10–95)% of heat content trip
±2.0% of heat content trip
1MRK 504 155-BEN F
Transformer protection RET670 2.1 IEC
ABB
81
