MIL-DTL-17060G(SH)
(2) Design B (see 6.6.26.2)
(3) Design B7 (see 6.6.26.3)
(4) Design C (see 6.6.26.4)
(5) Design D (see 6.6.26.5)
(6) Design F (see 6.6.26.6)
(7) Design FF (see 6.6.26.7)
Synchronous (see 6.6.27):
b.
(1) Permanent magnet:
(a)
Radial gap type
(b) Axial gap type
3.5.1.12 Full-load power factor, designs A, B, and B7.
3.5.1.12.1 Single speed induction motors. The full-load power factor (see 6.6.18) for single speed induction
motors shall be not less than 0.80 except for single speed induction motors 15 hp and less, or single speed induction
motors with synchronous speeds of 900 r/min and less, which shall be not less than 0.70. Motors with synchronous
speeds of 600 r/min and less need not conform to this requirement.
3.5.1.12.2 Multispeed induction motors. The full-load power factor for the high speed of a multispeed
induction motor shall be not less than 0.05 below that of a motor of the single speed rating.
3.5.1.13 Structureborne noise. The following factors shall be considered by the contractor in the design of the
motors to meet the requirements of 3.6.3.2:
Precision machining of rolling, rubbing, and fitting parts.
a.
b. Minimize imbalance incurred during the production phase to minimize corrections required during the final
balancing phase.
c.
Provisions for in-place balancing of rotating parts and access for in-place balancing.
d. Sharp cutoffs and turbulence avoided in the air cooling system. Ventilation ducts and housings damped to
prevent flow-excited vibration.
e.
Number of slots per pole.
f.
Proximity of the slot frequency to the natural frequency of the magnetic frame.
g.
Skewing of stator or rotor slots.
h.
Magnetic core and tooth flux densities.
i. Frequency and amplitude of structureborne noise to accommodate noise limits specified for the auxiliary
and motor assembly.
3.5.1.14 Mechanical fasteners. Mechanical fasteners shall be in accordance with MIL-E-917. Thread
engagement for mechanical fasteners, where mating materials are similar or dissimilar, shall be in accordance with
FED-STD-H28 (see MIL-E-917).
3.5.1.15 Mechanical balance. The rotating assemblies of motors shall be mechanically balanced at all loads
and speeds in the operating range to meet the required levels of balance and structureborne noise. Mechanical
balance correction shall be effected by the following methods:
a. Balance ring(s) shall be provided when super-precision levels of balance are specified and shall be in
accordance with MIL-E-917 and the following. Balance rings shall be located outboard of the bearings and shall
provide a fine adjustment for balance correction. Other balancing methods, as described in subparagraph (b) below,
shall be used to obtain the majority of the balance correction.
b.
The following methods of balance correction are listed in their order of preference:
(1) Weight removal.
(2) Weight addition - weights shall be securely attached to the rotating assembly.
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