An Investigation of Explosion-Proof Motors Page: 32
56 p. : ill.View a full description of this report.
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32
EXPLOSION-PROOF MOTORS.
TABLE 3.-Results of tests of type D protective devices.Group Motor
No. condition.1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25At rest,
with fan.
...do.......
...do.......
...do.......
...do.......
...do.......
...do.......
...do.......
...do.......
. ..do.......
...do.......
At rest,
without
fan.
...do.......
Running,
with fan.
...do........
...do......
...do.......
...do.......
...do.....
...do.......
Running,
without
fan.
...do.......
...do.......Gas
Ier-
cent-
age.
8.6
8.6
a8.6
a8.6
9.0
9.5
10.0
10.5
11.0
8.0
7.5
7.0
6.5
8.6
7.5
8.6
7.0
8.6
8.6
8.6
7.0
6.5
8.6Ignition point.
Commutator..
Field..........
Commutator..
Field.........
Commutator..
....do.........
.....do........
.....do.........
.....do .........
.....do.........
.....do.........
.....do.........
.....do.........
Shell ..........
.....do.........
Brush.........
.....do.........
Shell..........
.....do.........
.....do.........
.....do........
.....do........
.....do........8.6 .....do........
7.5 .....do.Maxi-
mum
pres-
sure.
Lbs. per
sq. in.
14.1
20.0
13.2
18.6
13.3
8.4
7.5
2.5
0.8
12.6
7.7
3.1
2.3
3.0
2.1
32.1
20.0
24.0
29.6
34.6
16.5
11.2
12.4Out-
side
flames.
No....
No....
No... -
No ....
No....
No....
No ....
No ....
No ....
No....
No....
No ....
No ....
Nob...
Nob...
Yes...
Yes...
Yes...
Yes...
Yes...
Yes...
Yes...
No d...12.2 Nod...
8.5 No....Typicalpressure
diagram.
Card Figure
No. No.D-42
D-87
D-145
D-229
D-95
D-113
D-27
D-132
D-141
D-40
D-58
D-74
D-78
D-203
D-205
D-187
D-161
D-194
D-194
D-194
D-195
D-195
D-199
D-199
D-20010
10
10
10
10
10
10
10
10
.0
10
10
10
11
11
11
11
11
11
11
11
11
11Num-
ber of
tests
made.
11
13
10
11
10
10
11
10
10
10
10
10
11
2
2
9
1
1
1
1
1
2Num-
ber of
"punc-
tures."
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2
0
0
0
0
0
0
011 1
11 1Speed
of
motor.
R.P. M.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
c1,250
c1,250
'1,250
1,510
1,790
1,250
1,250
1,2500 1,500
0 1,250aIn this group of tests finely ground coal dust was sifted between the plates of the protective devices
before each test.
b After-burning started at once and lasted for about 15 seconds.
c Normal speed.
dAfter-burning started at once and continued as long as the motor was running. Current was cut off
the motor as soon as the explosion took place, but the motor did not stop for nearly a minute.
DISCUSSION OF TEST RESULTS.
GENERAL REVIEW.
One hundred and forty-one satisfactory tests were made with the
motor at rest, and in none of these tests did "puncture" take place.
Thirteen tests were made with the motor running at normal speed
with the fan in place. "Puncture" occurred in two of these tests,
and probably would have taken place in at least three others if the
tests had been continued to the limit.
Four tests were made with the motor running without fan.
"Puncture" did not occur in any of these tests, but "after-burning"
began immediately after the explosion, and would have continued
indefinitely if the motor had not been stopped. The continuance of
"after-burning " would have soon burned the insulation from the
armature coils; but that the plates would have become sufficiently
heated to allow the flame to pass out against the entering gas current
is not certain.
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Clark, H. H. An Investigation of Explosion-Proof Motors, report, 1912; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc12261/m1/44/?q=%22United+States.+Bureau+of+Mines.%22: accessed June 14, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.