MIL-DTL-17060G(SH)
6.6.22 Resistance balance. The resistance balance is equal to the difference between the maximum and
minimum terminal-to-terminal winding resistance divided by the average terminal-to-terminal winding resistance.
6.6.23 Rigid shaft design. A motor design where the shaft critical speeds are in excess of the motor operating
speed.
6.6.24 Sealed insulation system. A sealed insulation system is an insulation system which through the use of
materials and processes, seals the windings and protects them against contaminants found in severe environmental
conditions.
6.6.25 Speed. The following definitions apply to speed:
6.6.25.1 Constant-speed motor. A constant-speed motor is one in which the normal speed of operation is
constant or constant within tolerances; for example, a synchronous motor or an induction motor with small slip.
6.6.25.2 Multispeed motor. A multispeed motor is one which can be operated at any of two or more definite
speeds, each being practically independent of the load.
6.6.25.3 Adjustable speed motor. An adjustable speed motor is one in which the speed can be varied gradually
over a considerable range, but when once adjusted remains practically unaffected by the load; for example, a
commutator motor with brush-shifting feature. The base speed of an adjustable speed motor is the lowest speed
obtained at rated load and rated voltage at normal operating temperatures.
6.6.25.4 Varying speed motor. A varying speed motor is one in which the speed varies with the load,
ordinarily decreasing when the load increases, such as a high-slip motor.
6.6.25.5 Adjustable varying speed motor. An adjustable varying speed motor is one in which the speed can be
adjusted gradually, but when once adjusted for a given load, will vary in considerable degree with change in load,
such as a wound rotor induction motor.
6.6.25.6 Base speed and speed variation for VSD motors. The base speed is the speed of operation with 60
hertz power applied to the motor. With variable frequency and voltage from the VSD, operation below and above
the base speed are possible.
6.6.26 Squirrel-cage induction motor. A squirrel-cage induction motor is one in which the secondary circuit of
a squirrel-cage winding is disposed in the secondary core.
6.6.26.1 Design A. Design A motors have characteristics similar to design B motors except that breakdown
torques and starting currents are higher. Because of higher starting currents, these motors are limited in their
applications onboard ships.
6.6.26.2 Design B. Design B motors are standard general purpose motors having low starting current, normal
torque and normal slip. These motors are widely used in such Naval shipboard applications as pumps, fans, blowers
and machine tools where the characteristics of the design B7 motor are not appropriate for the application.
6.6.26.3 Design B7. Design B7 motors are high efficiency motors normally applied to centrifugal loads where
high shaft connected inertia, accelerating under excessive loads, or rapid accelerating times are not a concern.
Design B7 motors are similar to design B motors except that their locked-rotor and pull-up torques are permitted to
be lower than design B, and the locked-rotor current may be higher than design B.
6.6.26.4 Design C. Design C motors have high breakaway torque, low starting currents and normal slip. These
motors are suitable for applications requiring high breakaway torques during starting, such as compressors,
conveyors and reciprocating pumps.
6.6.26.5 Design D. Design D motors have a high breakaway torque with high slip. These motors are suitable
for high inertia loads such as punch presses, shears, or other high inertia auxiliaries where energy is stored in fly
wheel under heavy fluctuating load conditions.
6.6.26.6 Design F. Design F motors have low starting torque, low starting current and low breakdown torque.
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