14

System

pro M compact ®

Miniature circuit-breakers

S 200/S 200 M series

The influence of ambient temperature and interdependencies in the case of even loads on the load

capability of MCBs

Practical Note: This practical deduction, that is applicable for all types of characteristics, can be recommended for standard

environments. Selection criteria for rated current of circuit-breakers according to EN 60898 and EN 60947-2.

Choose the circuit-breaker that is appropriate for the lower of the rated value of the device or the permissible current loading.

Now, the major factors having an influence on the circuit-breaker, must be taken into account:

1.

ambient temperature with I

B

0.9 x I

n at 40 °C ambient temperature

2.

mutual influence with I

B

0.75 x I

n in the case of more than one circuit-breaker being loaded evenly in parallel.

The ensuing rated current of the circuit breaker is thus: I

n = 1.5 x rated current

Example: operating currect 4 A, then the rated current of the circuit-breaker is: I

n = 1.5 x 4 A = 6 A

The above takes into account all relevant factors and the circuit is protected at the lowest possible level.

This practical note is based on the following:

1. Deviating ambient temperature: The thermal releases are adapted to a given reference ambient temperature. For the K- and Z-type

characteristics, it is 20 °C, for B-, C- and D-type, it is 30 °C.

For all other ambient temperatures, the current values indicated vary by ca. 6 % per 10 K temperature de/increase.

For more precise calculations and very high/low ambient temperatures, the following tables apply:

Max. operating current depending on the ambient temperature circuit-breaker in load circuit of characteristics type B, C and D

B, C and D

Ambient temperature T (°C)

I

n

(A)

– 40

– 30

– 20

– 10

0

10

20

30

40

50

60

70

0.5

0.67

0.65

0.62

0.60

0.58

0.55

0.53

0.50

0.47

0.44

0.41

0.37

1.0

1.33

1.29

1.25

1.20

1.15

1.11

1.05

1.00

0.94

0.88

0.82

0.75

1,6

2.13

2.07

2.00

1.92

1,85

1.77

1.69

1.60

1.51

1.41

1.31

1.19

2,0

2.67

2.58

2.49

2.40

2.31

2.21

2.11

2.00

1.89

1.76

1.63

1.49

3,0

4.0

3.9

3.7

3.6

3.5

3.3

3.2

3.0

2.8

2.6

2.4

2.2

4,0

5.3

5.2

5.0

4.8

4.6

4.4

4.2

4.0

3.8

3.5

3.3

3.0

6,0

8.0

7.7

7.5

7.2

6.9

6.6

6.3

6.0

5.7

5.3

4.9

4.5

8,0

10.7

10.3

10.0

9.6

9.2

8.8

8.4

8.0

7.5

7.1

6.5

6.0

10,0

13.3

12.9

12.5

12.0

11.5

11.1

10.5

10.0

9.4

8.8

8.2

7.5

13,0

17.3

16.8

16.2

15.6

15.0

14.4

13.7

13.0

12.3

11.5

10.6

9.7

16,0

21.3

20.7

20.0

19.2

18.5

17.7

16.9

16.0

15.1

14.1

13.1

11.9

20,0

26.7

25.8

24.9

24.0

23.1

22.1

21.1

20.0

18.9

17.6

16.3

14.9

25,0

33.3

32.3

31.2

30.0

28.9

27.6

26.4

25.0

23.6

22.0

20.4

18.6

32,0

42.7

41.3

39.9

38.5

37.0

35.4

33.7

32.0

30.2

28.2

26.1

23.9

40,0

53.3

51.6

49.9

48.1

46.2

44.2

42.2

40.0

37.7

35.3

32.7

29.8

50,0

66.7

64.5

62.4

60.1

57.7

55.3

52.7

50.0

47.1

44.1

40.8

37.3

63,0

84.0

81.3

78.6

75.7

72.7

69.6

66.4

63.0

59.4

55.6

51.4

47.0

Max. operating current depending on the ambient temperature circuit-breaker in load circuit of characteristics type K and Z

K and Z

Ambient temperature T (°C)

I

n (A)

– 40

– 30

– 20

– 10

0

10

20

30

40

50

60

70

0.5

0.66

0.64

0.61

0.59

0.56

0.53

0.50

0.47

0.43

0.40

0.35

0.31

1.0

1.32

1.27

1.22

1.17

1.12

1.06

1.00

0.94

0.87

0.79

0.71

0.61

1.6

2.12

2.04

1.96

1.88

1.79

1.70

1.60

1.50

1.39

1.26

1.13

0.98

2.0

2.65

2.55

2.45

2.35

2.24

2.12

2.00

1.87

1.73

1.58

1.41

1.22

3.0

4.0

3.8

3.7

3.5

3.4

3.2

3.0

2.8

2.6

2.4

2.1

1.8

4.0

5.3

5.1

4.9

4.7

4.5

4.2

4.0

3.7

3.5

3.2

2.8

2.4

6.0

7.9

7.6

7.3

7.0

6.7

6.4

6.0

5.6

5.2

4.7

4.2

3.7

8.0

10.8

10.2

9.8

9.4

8.9

8.5

8.0

7.5

6.9

6.3

5.7

4.9

10.0

13.2

12.7

12.2

11.7

11.2

10.6

10.0

9.4

8.7

7.9

7.1

6.1

13.0

17.2

16.6

15.9

15.2

14.5

13.8

13.0

12.2

11.3

10.3

9.2

8.0

16.0

21.2

20.4

19.6

18.8

17.9

17.0

16.0

15.0

13.9

12.6

11.3

9.8

20.0

26.5

25.5

24.5

23.5

22.4

21.2

20.0

18.7

17.3

15.8

14.1

12.2

25.0

33.1

31.9

30.6

29.3

28.0

26.5

25.0

23.4

21.7

19.8

17.7

15.3

32.0

42.3

40.8

39.2

37.5

35.8

33.9

32.0

29.9

27.7

25.3

22.6

19.6

40.0

52.9

51.0

49.0

46.9

44.7

42.4

40.0

37.4

34.6

31.6

28.3

24.5

50.0

66.1

63.7

61.2

58.6

55.9

53.0

50.0

46.8

43.3

39.5

35.4

30.6

63.0

83.3

80.3

77.2

73.9

70.4

66.8

63.0

58.9

54.6

49.8

44.5

38.6

2. Interdependencies in

the case of even loads

A correction factor must be

taken into account in the

case butt-mounted devices

and an evenly applied, high

load:

2 and 3 circuit-breakers

with factor 0.9

4 and 5 circuit-breakers

with factor 0.8

6 and more circuit-breakers

with factor 0.75

T

he interdependency

becomes irrelevant if

FST … spacers or

packing blocks (9mm

width) are used.

The influence of ambient temperature and interdependencies in the case of even loads on the load

capability of MCBs

Practical Note: This practical deduction, that is applicable for all types of characteristics, can be recommended for standard

environments. Selection criteria for rated current of circuit-breakers according to EN 60898 and EN 60947-2.

Choose the circuit-breaker that is appropriate for the lower of the rated value of the device or the permissible current loading.

Now, the major factors having an influence on the circuit-breaker, must be taken into account:

1.

ambient temperature with I

B

0.9 x I

n at 40 °C ambient temperature

2.

mutual influence with I

B

0.75 x I

n in the case of more than one circuit-breaker being loaded evenly in parallel.

The ensuing rated current of the circuit breaker is thus: I

n = 1.5 x rated current

Example: operating currect 4 A, then the rated current of the circuit-breaker is: I

n = 1.5 x 4 A = 6 A

The above takes into account all relevant factors and the circuit is protected at the lowest possible level.

This practical note is based on the following:

1. Deviating ambient temperature: The thermal releases are adapted to a given reference ambient temperature. For the K- and Z-type

characteristics, it is 20 °C, for B-, C- and D-type, it is 30 °C.

For all other ambient temperatures, the current values indicated vary by ca. 6 % per 10 K temperature de/increase.

For more precise calculations and very high/low ambient temperatures, the following tables apply:

Max. operating current depending on the ambient temperature circuit-breaker in load circuit of characteristics type B, C and D

B, C and D

Ambient temperature T (°C)

I

n

(A)

– 40

– 30

– 20

– 10

0

10

20

30

40

50

60

70

0.5

0.67

0.65

0.62

0.60

0.58

0.55

0.53

0.50

0.47

0.44

0.41

0.37

1.0

1.33

1.29

1.25

1.20

1.15

1.11

1.05

1.00

0.94

0.88

0.82

0.75

1,6

2.13

2.07

2.00

1.92

1,85

1.77

1.69

1.60

1.51

1.41

1.31

1.19

2,0

2.67

2.58

2.49

2.40

2.31

2.21

2.11

2.00

1.89

1.76

1.63

1.49

3,0

4.0

3.9

3.7

3.6

3.5

3.3

3.2

3.0

2.8

2.6

2.4

2.2

4,0

5.3

5.2

5.0

4.8

4.6

4.4

4.2

4.0

3.8

3.5

3.3

3.0

6,0

8.0

7.7

7.5

7.2

6.9

6.6

6.3

6.0

5.7

5.3

4.9

4.5

8,0

10.7

10.3

10.0

9.6

9.2

8.8

8.4

8.0

7.5

7.1

6.5

6.0

10,0

13.3

12.9

12.5

12.0

11.5

11.1

10.5

10.0

9.4

8.8

8.2

7.5

13,0

17.3

16.8

16.2

15.6

15.0

14.4

13.7

13.0

12.3

11.5

10.6

9.7

16,0

21.3

20.7

20.0

19.2

18.5

17.7

16.9

16.0

15.1

14.1

13.1

11.9

20,0

26.7

25.8

24.9

24.0

23.1

22.1

21.1

20.0

18.9

17.6

16.3

14.9

25,0

33.3

32.3

31.2

30.0

28.9

27.6

26.4

25.0

23.6

22.0

20.4

18.6

32,0

42.7

41.3

39.9

38.5

37.0

35.4

33.7

32.0

30.2

28.2

26.1

23.9

40,0

53.3

51.6

49.9

48.1

46.2

44.2

42.2

40.0

37.7

35.3

32.7

29.8

50,0

66.7

64.5

62.4

60.1

57.7

55.3

52.7

50.0

47.1

44.1

40.8

37.3

63,0

84.0

81.3

78.6

75.7

72.7

69.6

66.4

63.0

59.4

55.6

51.4

47.0

Max. operating current depending on the ambient temperature circuit-breaker in load circuit of characteristics type K and Z

K and Z

Ambient temperature T (°C)

I

n (A)

– 40

– 30

– 20

– 10

0

10

20

30

40

50

60

70

0.5

0.66

0.64

0.61

0.59

0.56

0.53

0.50

0.47

0.43

0.40

0.35

0.31

1.0

1.32

1.27

1.22

1.17

1.12

1.06

1.00

0.94

0.87

0.79

0.71

0.61

1.6

2.12

2.04

1.96

1.88

1.79

1.70

1.60

1.50

1.39

1.26

1.13

0.98

2.0

2.65

2.55

2.45

2.35

2.24

2.12

2.00

1.87

1.73

1.58

1.41

1.22

3.0

4.0

3.8

3.7

3.5

3.4

3.2

3.0

2.8

2.6

2.4

2.1

1.8

4.0

5.3

5.1

4.9

4.7

4.5

4.2

4.0

3.7

3.5

3.2

2.8

2.4

6.0

7.9

7.6

7.3

7.0

6.7

6.4

6.0

5.6

5.2

4.7

4.2

3.7

8.0

10.8

10.2

9.8

9.4

8.9

8.5

8.0

7.5

6.9

6.3

5.7

4.9

10.0

13.2

12.7

12.2

11.7

11.2

10.6

10.0

9.4

8.7

7.9

7.1

6.1

13.0

17.2

16.6

15.9

15.2

14.5

13.8

13.0

12.2

11.3

10.3

9.2

8.0

16.0

21.2

20.4

19.6

18.8

17.9

17.0

16.0

15.0

13.9

12.6

11.3

9.8

20.0

26.5

25.5

24.5

23.5

22.4

21.2

20.0

18.7

17.3

15.8

14.1

12.2

25.0

33.1

31.9

30.6

29.3

28.0

26.5

25.0

23.4

21.7

19.8

17.7

15.3

32.0

42.3

40.8

39.2

37.5

35.8

33.9

32.0

29.9

27.7

25.3

22.6

19.6

40.0

52.9

51.0

49.0

46.9

44.7

42.4

40.0

37.4

34.6

31.6

28.3

24.5

50.0

66.1

63.7

61.2

58.6

55.9

53.0

50.0

46.8

43.3

39.5

35.4

30.6

63.0

83.3

80.3

77.2

73.9

70.4

66.8

63.0

58.9

54.6

49.8

44.5

38.6