MIL-DTL-17060G(SH)
3.5.1 General. Service A and Service C motors shall meet the requirements of 3.5.1.1 through 3.5.1.38.
3.5.1.1 Voltage and frequency variation. Motors shall operate in accordance with the requirements of this
specification at rated voltage and frequency. Motors shall perform satisfactorily when operated with a variation in
voltage or frequency as follows:
a.
±10 percent of rated voltage, with rated frequency.
b.
±5 percent of rated frequency, with rated voltage.
c. A combined variation in voltage and frequency of 10 percent (sum of absolute values) of rated values,
provided the frequency variation does not exceed ±5 percent of rated frequency.
3.5.1.2 Rated voltage and frequency. Motors shall operate with the following rated voltages and frequencies,
as specified (see 6.2):
a.
Voltage:
(1) 220 volts alternating current (Vac)
(2) 440 Vac
(3) 115 Vac
(4) Special
b.
Frequency:
(1) 60 hertz
(2) Special
3.5.1.3 Ambient temperature. Motors shall operate in accordance with this specification in the following
ambient temperature as specified (see 6.2):
104 degrees Fahrenheit (°F) [40 degrees Celsius (°C)]
a.
b.
122 °F (50 °C)
c.
149 °F (65 °C)
d.
158 °F (70 °C)
e.
176 °F (80 °C) or more
3.5.1.4 Winding. Motors shall be wound by use of coils preformed or mush wound coils without recourse to
special equipment beyond that normally available at field electric repair facilities. Motor windings shall have an
integral number of turns per coil or shall be half-turn windings.
3.5.1.5 Air gap. Motors shall be constructed for a minimum air gap of not less than 0.0025 inch per inch of
rotor outside diameter except a minimum air gap of 0.012 inch for rotor diameters 4.8 inches or less.
3.5.1.6 Duty and duty cycle. Duty of motors shall be continuous, intermittent, varying or short-time, as
specified (see 6.2). Motors of other than continuous duty shall have a defined duty cycle (see 6.2).
3.5.1.7 Thermal protection. When specified (see 6.2), motors shall be provided with thermal protection (see
6.6.28) for the stator windings. A minimum of two thermal sensors per phase, located in the same pole-phase group,
shall be imbedded in the stator winding. The pole-phase groups, with sensors, shall be equally spaced about the
stator diameter. Sensor leads shall be flexible and shall be secured to the coilhead at a location near where they will
exit the coilhead to prevent force from being transmitted to the sensor. For one sensor per phase, the lead length
extending beyond the point where they are secured to the coilhead shall be coiled and tied to the coilhead. When
specified (see 6.2), motors shall be provided with a minimum of one thermal sensor in contact with each bearing
outer ring. Where the sensors used are thermistors, thermal protection shall be provided in accordance with
MIL-M-24738. Thermal sensors shall be monitored with one sensing network (monitor) that shall energize an alarm
or de-energize the motor control within ±41 °F (5 °C) of the set point of the thermal sensor.
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