Technical Data
Operational Characteristics
Thermal Curve
In accordance with IEC 60255-8 Thermal Electrical Relays specifications, protection functions activate based on hot curves and cold
curves depending on the thermal characteristics of the load current before an overload can occur. The operating characteristic curves
are as shown on the graph, represented as functions of current and time from class 1 to 60.
The relay takes real-time measurement of motor heating accumulation, and in the event of an overload activates the protection function
that is optimized to the motor’s operational conditions based on the cumulative heat data.
The formula for each operating characteristic curve can be represented as follows:
Cold curve indicates that the load current before the overload, I
P
is zero in the hot curve formula.
Item
Details
t
Operating Time
Duration of the operation of the relay.
τ
Time Constant
According to the above OC formula, the values for time constant τ for time T under 600 % of rated current and
k = 1.1 are as follows.
T
1
10
20
30
40
50
60
τ
29.25
292.49
584.98
877.48
1,169.97
1,462.46
1,754.95
I
B
Rated Load Current
Rated current set value
I
Fault Current (Input Current)
Fault current value where a trip occurs. The reference value is six times (600 %) the rated current.
I
P
Load Current Before Overload
Load current recorded by the relay prior to the overload.
k
Overload Factor
Represents the motor’s service factor value. K = 1.1
Hot Curve
I
2
- I
p
2
I
2
- (kI
B
)
2
[
sec
]
t = τln
Cold Curve
I
2
I
2
- (kI
B
)
2
[
sec
]
t = τln
0.01
1
1
10
0.1
10
100
1,000
10,000
Oper
ating Time
Current
Hot Class 1
Hot Class 10
Hot Class 20
Hot Class 30
Hot Class 40
Hot Class 50
Hot Class 60
Cold Class 1
Cold Class 10
Cold Class 20
Cold Class 30
Cold Class 40
Cold Class 50
Cold Class 60
16
Electronic Motor Protection Relays
Summary of Contents for Earth Leakage HGMP N60 Z
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