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■ Rated currents of 3-phase motors (approx. figures for squirrel-cage motors)
Minimum fuse size for protection of 3-phase motors
The maximum size is determined by the requirements of the switchgear or overload relay.
The rated motor currents are for standard 1500 r.p.m. 3-phase enclosed ventilated and totally enclosed fan-cooled motors.
D.O.L. starting:
Maximum starting current 6 x rated motor current. Maximum starting time 5 s.
Y/D starting:
Maximum starting current 2 x rated motor current. Maximum starting time 15 s.
Set overload relay in the phase lead to 0.58 x rated motor current.
Rated fuse currents for Y/D starting are also valid for 3-phase motors with slip-ring motors.
For higher rated currents, starting currents and/or longer starting times, larger fuses are required.
Table is valid for "slow" and/or "gL" fuses (DIN VDE 0636).
For NH fuses with aM characteristics, fuses = rated current is selected.
Motor rating
cos ϕ
η %
kW
0.06
0.7
58
0.09
0.7
60
0.12
0.7
60
0.18
0.7
62
0.25
0.7
62
0.37
0.72
66
0.55
0.75
69
0.75
0.79
74
1.1
0.81
74
1.5
0.81
74
2.2
0.81
78
3.0
0.82
80
4.0
0.82
83
5.5
0.82
86
7.5
0.82
87
11.0
0.84
87
15.0
0.84
88
18.5
0.84
88
22.0
0.84
92
30.0
0.85
92
37.0
0.86
92
45.0
0.86
93
55.0
0.86
93
75.0
0.86
94
90.0
0.86
94
110.0
0.86
94
132.0
0.87
95
160.0
0.87
95
200.0
0.87
95
250.0
0.87
95
315.0
0.87
96
400.0
0.88
96
450.0
0.88
96
500.0
0.88
97
560.0
0.88
97
630.0
0.88
97
230 V
Rated
Fuse
motor
starting
current
D.O.L.
Y/∆
A
A
A
0.37
2.0
-
0.54
2.0
-
0.72
4.0
2
1.04
4.0
2
1.4
4.0
2
2.0
6.0
4
2.7
10.0
4
3.2
10.0
4
4.6
10.0
6
6.3
16.0
10
8.7
20.0
10
11.5
25.0
16
14.8
32.0
16
19.6
32.0
25
26.4
50.0
32
38.0
80.0
40
51.0
100.0
63
63.0
125.0
80
71.0
125.0
80
96.0
200.0
100
117.0
200.0
125
141.0
250.0
160
173.0
250.0
200
233.0
315.0
250
279.0
400.0
315
342.0
500.0
400
401.0
630.0
500
486.0
630.0
630
607.0
800.0
630
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
400 V
Rated
Fuse
motor
starting
current
D.O.L.
Y/∆
A
A
A
0.21
2.0
-
0.31
2.0
-
0.41
2.0
-
0.6
2.0
-
0.8
4.0
2
1.1
4.0
2
1.5
4.0
2
1.9
6.0
4
2.6
6.0
4
3.6
6.0
4
5.0
10.0
6
6.6
16.0
10
8.5
20.0
10
11.3
25.0
16
15.2
32.0
16
21.7
40.0
25
29.3
63.0
32
36.0
63.0
40
41.0
80.0
50
55.0
100.0
63
68.0
125.0
80
81.0
160.0
100
99.0
200.0
125
134.0
200.0
160
161.0
250.0
200
196.0
315.0
200
231.0
400.0
250
279.0
400.0
315
349.0
500.0
400
437.0
630.0
500
544.0
800.0
630
683.0
1000.0
800
769.0
1000.0
800
-
-
-
-
-
-
-
-
-
Low Voltage Switch Gear
415 V
Rated
Fuse
motor
starting
current
D.O.L.
Y/∆
A
A, BS
A, BS
0.21
2.0
2
0.30
2.0
2
0.40
2.0
2
0.58
2.0
2
0.8
4.0
2
1.1
4.0
2
1.5
6.0
4
1.8
6.0
4
2.6
10.0
6
3.5
16.0
10
4.8
16.0
10
6.4
20.0
16
8.2
20.0
16
10.9
25.0
20
14.6
35.0
25
20.9
50.0
32
28.2
80.0
40
35.0
80.0
50
40.0
80.0
50
53.0
100.0
80
65.0
125.0
80
78.0
125.0
80
96.0
160.0
100
129.0
250.0
160
155.0
250.0
160
189.0
315.0
200
222.0
355.0
250
269.0
355.0
315
337.0
450.0
355
421.0
500.0
450
525.0
630.0
560
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
Appendix
101
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