Siemens 7SG23 MSCDN - MP2A, Руководство пользователя

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MSCDN – MP2A Applications Guide
Resistor Thermal Characteristics
CURRENT IN AMPS TIME IN SECS RELAY CHARACTERISTICS
12.00 Continuous Continuous
16.00 20.00 10.27
19.00 9.00 5.93
20.00 8.00 5.15
21.00 7.00 4.52
22.00 6.00 4.02
23.00 5.00 3.60
25.00 4.00 2.94
28.00 3.00 2.26
34.00 2.00 1.47
Steady state thermal energy =
% 100
2
2
× =
θ
θ
I
I
F
% 64 . 82 % 100
1 . 1
1
2
2
= × =
F
θ
Alarm level thermal state =
% 91 % 100
1 . 1
05 . 1
2
2
= × =
F
θ
Re-arranging equation 1 we get
⎪⎭
⎪
⎬
⎫
⎪⎩
⎪
⎨
⎧
⎥
⎥
⎦
⎤
⎢
⎢
⎣
⎡
×
×
− × − =
100
1 ln
2
2
I
I
t
θ
θ
τ
…. (Eq.5)
The maximum operating time of the Thermal Alarm (i.e. from cold) will given by :-
θ
= 91 %
τ =
9 s
I = 1.05
I
θ
= 1.1
t = 60.02 s
To achieve steady state thermal capacity of 82.6% (i.e. from cold) will given by :-
θ
= 82.6 %
τ =
9 s
I = 1.05
I
θ
= 1.1
t = 21.33 s
Therefore the operating time from steady state at rated current of the Thermal Alarm would be
t = 60s – 21.3s = 38.7s
Thermal Protection Settings
R1 & R2 49 Overload Setting (using 1A i/p) 0.66 xIn
R1 & R2 49 Time Constant 9 seconds
R1 & R2 49 Capacity Alarm 91 %
©2010 Siemens Protection Devices Limited Chapter 5 Page 6 of 7