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Page Title:
Controllers and master switches |
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|  MIL-C-18419B(SHIPS)
Duty . . . . . . . . . . . . . Same as motor (see
3.5.1.2.2 The hot full-field no-load speed at any
3.5.1).
voltage from 70 percent of nominal to 142 percent
Master switches
of nominal, shall not exceed 90 percent of the maxi-
required . . . . . . . . . (See 3.5.2.2)
mum safe operating speed of the compressors as
Master switch enclo-
established by the compressor manufacturer. These
sures . . . . . . . . . . . Spray tight (remote);
speeds shall be shown on the motor and compressor
dripproof (local).
drawings.
Master Switch location Remote or local.
3.5.1.2.3 Motors shall be capable of being
3.5.2.1 Each controller shall be provided with
started at all voltages within the varying voltage
an automatic timing device which will permit the
range specified, assuming that at the instant of
compressor to run after starting for a sufficient
starting the compressors will always be unloaded
period to buildup lube oil pressure, but after which
(see 3.3.21).
the compressor will automatically stop if the lube
oil failure switch on the compressor has not closed
3.5.1.2.4 Motors shall be equipped with over-
(see 3.3.1.5. 4). Terminal connections shall be
speed trips unless the conditions specified in
provided for all other auxiliary devices (see
3.5.1.2.5 are met. Motors shall be mechanically
3.3. 15.7 and 3.3.22. 3). The terminal *connections
capable of operating at a speed of 10 percent above
for electric heaters (see 3.3.15. 7) shall be pro-
the setting of the overspeed trip. If no overspeed
vided in ail cases, whether or not heaters are re-
trip is provided then the motors shall be mechan-
quired by the contract or order.
ically capable of operating at a speed of 10 percent
above the hot no-load speed at 142 percent rated
3.5.2.2 Except for d. c. submarine service
voltage with a field circuit resistance equal to 110
each controller shall be provided with remote "ON",
percent of the rated resistance value of the field
"OFF", push buttons, a local two-position
rheostat.
"MANUAL-AUTOMATIC" switch and a remote pres-
sure switch. The push buttons shall be of the
3.5.1.2.5 Consideration will be given to omis-
momentary contact type. With the "MANUAL-
sion of field rheostats and overspeed trips if all the
AUTOMATIC" switch in the "AUTOMATIC" posi-
following conditions are met:
tion, pressing the "Oh'" push button shall prepare
the circuit for operation under automatic control of
(a) At rated voltage and full field hot, the
the pressure switch. When the air pressure in the
full-load speed will be the rated speed
discharge line is below the value set on the pres-
required by the compressor for rated
sure switch, the pressure switch shall close and
output.
start the compressor. The compressor shall con-
(b) Requirements of 3,5. 1.2.2 are met.
tinue to run until the pressure rises to the value re-
(c) At 80 percent of rated voltage, full field
quired to open the pressure switch causing the
hot and load encountered at rated com-
controller to stop the compressor. When the pres-
pressor discharge pressure, the speed
sure again drips to the low setting of the pressure
will not be less than 75 percent of rated
switch the compressor shall start automatically.
full load, full voltage speed. This
This automatic operation shall continue in effect
speed should be shown on the motor
until the "OFF" push button is pressed. With the
drawings.
selector switch in the "MANUAL" position, the
compressor shall start when the "ON" push button
3. 5.2 Controllers and master switches. - All
is pressed, provided the pressure switch is closed,
controllers and master switches shall be in accord-
and shall continue to run until the "OFF" push but-
ance with MI L-C-2212 for a. c. equipment, or MIL-
ton is pressed, or until the pressure switch opens.
C-2174 for d. c. equipment, and the following:
The compressor shall not then restart until the
Dripproof.
"ON" push button is again pressed.
Enclosure
Magnetic.
Operation
3. 5.2.2.1 Motor overload or compressor over
50" C.
Ambient temperature .
temperature protection shall not be by-passed by
Insulation . . . . . . . . .
Class B (Class A for
the "ON" push button., Emergency run feature
coils only).
(see 3.5.2. 1.)
shall not be provided.
Performance . . . . . . .
A. c. motor starting.
Control function. . . . .
3.5.2.2.2 The pressure switch shall be in ac-
D. c. motor starting
cordance with MIL-C-2174 or MIL-C-2212 as
(see 3.5. 1.2).
applicable. The pressure switch shall be of an ad-
Type . . . . . . . . . . . .
A. c. across-the-line,
justable type, suitable for the maximum pressure
D. c. resistor, in-
ductive time lag
specified for the compressor and with a minimum
differential of not more than 6.7 percent of the
acceleration.
compressor rating.
Protection. . . . . . . . .
Overload, low voltage
protection (LVP).
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