|
Allowable Starts and
Starting Intervals
Design A and B Motors
| HP |
2 Pole |
4 Pole |
6 Pole |
| A |
B |
C |
A |
B |
C |
A |
B |
C |
1
1.5
2
3 |
15
12.9
11.5
9.9 |
1.2
1.8
2.4
3.5 |
75
76
77
80 |
30
25.7
23
19.8 |
5.8
8.6
11
17 |
38
38
39
40 |
34
29.1
26.1
22.4 |
15
23
30
44 |
33
34
35
36 |
5
7.5
10
15 |
8.1
7.0
6.2
5.4 |
5.7
8.3
11
16 |
83
88
92
100 |
16.3
13.9
12.5
10.7 |
27
39
51
75 |
42
44
46
50 |
18.4
15.8
14.2
12.1 |
71
104
137
200 |
37
39
41
44 |
20
25
30
40 |
4.8
4.4
4.1
3.7 |
21
26
31
40 |
110
115
120
130 |
9.6
8.8
8.2
7.4 |
99
122
144
189 |
55
58
60
65 |
10.9
10.0
9.3
8.4 |
262
324
384
503 |
48
51
53
57 |
50
60
75
100 |
3.4
3.2
2.9
2.6 |
49
58
71
92 |
145
170
180
220 |
6.8
6.3
5.8
5.2 |
232
275
338
441 |
72
85
90
110 |
7.7
7.2
6.6
5.9 |
620
735
904
1181 |
64
75
79
97 |
125
150
200
250 |
2.4
2.2
2.0
1.8 |
113
133
172
210 |
275
320
600
1000 |
4.8
4.5
4.0
3.7 |
542
640
831
1017 |
140
160
300
500 |
5.4
5.1
4.5
4.2 |
1452
1719
2238
2744 |
120
140
265
440 |
Where:
|
A = Maximum number of
starts per hour.
B = Maximum product of starts per hour times load Wk˛.
C = Minimum rest or off time in seconds between starts. |
Allowable starts per hour is the
lesser of (1) A or (2) B divided by the load Wk˛, i.e.,
|
Starts per hour <
A or
|
B
Load Wk˛
|
, whichever is less. |
Example:
|
25 hp, 4 pole, load Wk˛ = 50
From Table, A = 8.8, B = 122. |
|
Starts per hour =
|
122
50
|
= 2.44 |
Calculated value is less than A.
Therefore allowable starts/hour = 2.44.
Note: Table is based on following conditions:
- Applied voltage and frequency in
accordance with NEMA Standards MG 1-12.44.
- During the accelerating period, the
connected load torque is equal to or less than a torque which
varies as the square of the speed and is equal to 100 percent of rated
torque at rated speed.
- External load Wk˛ equal to or
less than the values listed in Column B.
For other conditions, consult the
manufacturer.
Reference: NEMA Standards MG 10, Table 2-3.
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|
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