MIL-PRF-18953C(SH)
For Types A and L fan, unless otherwise specified (see 6.2), Class F sealed insulation in
Insulation:
accordance with MIL-STD-2037. Motor temperature rise not to exceed 55 °C in a 65 °C
ambient.
For Types X-A and X-L fan, unless otherwise specified (see 6.2), Class F in accordance
with IEEE STD 45 with 55 °C maximum temperature rise in a 65 °C ambient.
See Table II
Horsepower:
Motors shall operate within the requirements specified herein when mounted in the
Mounting:
positions described in 3.10.2.
Motor, when specified, shall be equipped with thermal protection in each phase to detect
Protection:
over-temperature. Thermal protectors shall be of the automatic reset type with appropriate
locked rotor temperature limit. (see 6.2)
Drain holes with plugs shall be furnished in each spraytight motor to drain condensate from
Drains:
the motor when fan is installed vertically, with the impeller up or down or horizontally. For
drainage in the horizontal position, an adequate number of holes shall be provided to allow
360-degree rotation of the fan.
TABLE II. Motor requirements.
Min.
Torque
Lock
Fan
Fan
Nominal
No.
Power
Motor
rotor
Speed
Lock
Break
type
size
Hp
wind
60 Hz
Pull up
Eff. (%)
current
rotor
down
1
A and
¼
Single
1
75
/5
NEMA
X-A
½
Single
1
80
MG 11/
1
1
Single
1
86
NEMA
+
MG 11/
1½
1¼
Single
1
86
10
2
1½
Single
1
86
percent
2½
2
Single
1
87
3
3
Full
2
85
3½
3
Single
1
88
4½
5
Single
1
89
5
4
Full
2
85
70
70 percent
6
5
Full
2
86
percent
full load
440V - 3Ø
full load
7
7½
Full ½
2
88
torque
torque
8
6
Full
2
86
10
7½
Full
2
88
NEMA
NEMA
MG 12/
MG 12/
11
12½
Full
2
89
12
10
Full
2
89
16
15
Full
2
90
17
17½
Full
2
90
20
20
Full
2
90
25
25
Full ¾
2
91
28
25
Full
2
91
30
25
Full ¾
2
91
1
L and
NEMA
½
Single
1
22
115V - 1Ø
/15
MG 11/
X-L
1
Single
1
50
115V - 1Ø
NEMA
+
MG 11/
2
¼
Single
1
79
440V - 3Ø
10
79
3
¼
Single
1
440V - 3Ø
percent
1/
MIL-M-17059 may be used as an alternative.
2/
MIL-M-17060 may be used as an alternative.
3.11.1.2 Balancing. Motor rotating assembly shall be balanced in accordance with NEMA MG 1.
10
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