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Page Title:
Table II - Duty rating of motors. |
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|  MIL-P-21343(SHIPS)
3.5 M o t o r s . -
3.5.1 Al direct current (d.c.) motors for driving pumps shall be of the types and characteristics
specified and shall conform to Specification MIL-M-17413 except as modified herein:
Service - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Navy A.
Volts - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Varying as specified (see 6.1).
Adjustable varying.
Speed classification ---------------------
Duty - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Continuous and intermittent
(see table II).
Enclosure - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Dripproof protected.
Mounting - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Vertical, shall down
Ambient temperature - - - - - - - - - - - - - - - - - - -
50 C.
Winding - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Stabilized shunt.
lnsulation - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Class B.
Bearings - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Ball.
3.5.2 Motors shall be sized so as not to be overloaded at any possible operating point of the pumps
up to the maximum speed specified (see 6.1).
3.5.2.1 The motors shall conform to the duty ratings shown in table II.
Table II - Duty rating of motors.
maximum horsepower (hp. ) is the maximum hp. required by the pump under any condi-
tion of operation specified (see 6.1).
maximum speed is the maximum revolutions per minute (r.p.m.) required by the pump to
meet all conditions specified (see 6.1).
3.5.3 D.c. motors shall be mechanically capable of operating at a speed of 10 percent above the
setting of the overspeed trip, if one is provided. If no overspeed trip is provided, the motors shall be
mechanically capable of operating at a speed of 10 percent above the hot no-load speed at the maximum
voltage specified with 2 field resistance equal to 110 percent of the rated resistance value of the field
rheostat. The overspeed trip, if provided, shall be set at approximately 10 percent above maximum
rated speed.
2.5.4 Each d.c. motor shall be equipped with a reliable and accurate electric continuous speed
indicator apparatus consisting of a small permanent magnet type alternator permanently mounted on the
top of the motor, and a speed Indicating meter suitable for installation remote from the motor. A
terminal box shall be provided in the motor for connecting cable from alternator to meter, The cable
need not be supplied. The meter shall be suitable for bulkhead mounting and shall have a clear reading
90-degree arc scale not less than 3-3/4 inches long which will give accurate speed readings from
150 degrees to 3600 r. p. m. The speed indicator device and overspeed trip device may be combined in
one unit, if desired.
3.5.5 Motors shall be capable of being started over the entire voltage range specified (see 6.1),
assuming at the instant of starting, the motor need supply only sufficient torque to start the pump rotor.
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