MIL-PRF-19004B
3.16.7 Test connection for explosion-proof motors. A single drilled, tapped,
and plugged opening shall be provided in the front bracket of each explosion-
proof motor for determining enclosure air leakage rate.
3.16.8 Torque and locked rotor current.
Torque and locked rotor current
shall be as specified in Table III.
3.16.9 Speed-torque characteristics. The speed-torque characteristics shall
be coordinated with the combined inertia of the rotating assembly, including
fan impeller. It shall be possible to accelerate the fan unit from standstill
to high or low speed at 90 percent of the rated voltage when the current
rating of the controller overload protective device does not exceed the motor
full load current.
3.17
Fan performance.
3.17.1 Volume and pressure. The design point for each size of Navy standard
centrifugal fans is the volume-pressure point at the maximum total pressure
(TP) shown for that size on Table I and Figure 2. The TP shall rise
continually from free delivery to a value at least as high as the stated value
shown in Table I, and throughout this range shall exhibit stable performance.
3
Volume in ft /min shall be within 5 percent of the volume on the applicable
curve of Figure 2, as indicated on system characteristic curves. Total
pressure developed by a fan is the pressure at the fan discharge, and the
volume is the volume at fan inlet.
3.17.2 Aerodynamic stall. Effective stall shall not occur at capacities
greater than 85 percent of the air quantities given in Table I, for each fan
size.
TABLE
III.
Torque of motors, type CC and X-CC fans.
TORQUE
Locked
Pullup
Fan
Locked rotor current
rotor
Breakdown as
percent
Size
percent
specified
minimum
minimum
1/4
NEMA
MG
1
+ 10 percent
70
NEMA
MG
1
70
1/2
NEMA
MG
1
+ 10 percent
70
NEMA
MG
1
70
1
NEMA
MG
1
+ 10 percent
70
NEMA
MG
1
70
1-1/2
NEMA
MG
1
+ 10 percent
70
NEMA
MG
1
70
2
NEMA
MG
1
as specified
70
NEMA
MG
1
70
3
NEMA
MG
1
as specified
70
NEMA
MG
1
70
4
NEMA
MG
1
as specified
70
NEMA
MG
1
70
5
NEMA
MG
1
as specified
70
NEMA
MG
1
70
6
NEMA
MG
1
as specified
70
NEMA
MG
1
70
8
NEMA
MG
1
as specified
70
NEMA
MG
1
70
10
NEMA
MG
1
as specified
70
NEMA
MG
1
70
3.17.3 Airborne noise. The total sound power levels for the fan-motor unit
shall not exceed the levels stated in Table IV when measured in accordance
with procedures stated in 4.7.5. Exceeding the total sound power levels
specified in Table IV shall be cause for rejection.
9
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