U.S. patent application number 09/779272 was filed with the patent office on 2001-11-29 for locomotive air conditioner control system and related methods.
Invention is credited to Graham, Donald E., Hodapp, John M..
Application Number | 20010045101 09/779272 |
Document ID | / |
Family ID | 26877768 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010045101 |
Kind Code |
A1 |
Graham, Donald E. ; et
al. |
November 29, 2001 |
Locomotive air conditioner control system and related methods
Abstract
A locomotive cab air conditioning method involves providing a
multi-speed motor operable in at least a first speed state and a
second speed state, the motor connected for driving a refrigerant
compressor from a companion alternator output of the locomotive. An
operating speed of a locomotive engine is monitored, and operation
of the motor in one of the speed states is established based at
least in part upon the monitored locomotive engine speed.
Inventors: |
Graham, Donald E.; (Dayton,
OH) ; Hodapp, John M.; (Dayton, OH) |
Correspondence
Address: |
Thompson Hine & Flory LLP
Attention: Theodore D. Lienesh
2000 Courthouse Plaza N.E.
P.O. Box 8801
Dayton
OH
45401-8801
US
|
Family ID: |
26877768 |
Appl. No.: |
09/779272 |
Filed: |
February 8, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60182084 |
Feb 11, 2000 |
|
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|
Current U.S.
Class: |
62/236 ;
62/196.3 |
Current CPC
Class: |
B60H 1/3208 20130101;
B61D 27/0018 20130101; B61C 17/04 20130101; F25B 2600/0252
20130101 |
Class at
Publication: |
62/236 ;
62/196.3 |
International
Class: |
F25B 041/00; F25B
049/00; F25B 027/00 |
Claims
What is claimed is:
1. A locomotive cab air conditioning method, comprising: providing
a multi-speed motor operable in at least a first pole state and a
second pole state, the motor connected for driving a refrigerant
compressor from power derived from a companion alternator output;
monitoring a frequency or period of the companion alternator
output; and establishing operation of the motor in one of the pole
states based at least in part upon the monitored frequency or
period.
2. The method of claim 1 wherein the first pole state of the
multi-speed motor is a high speed, two-pole operating state and
wherein the second pole state of the multi-speed motor is a low
speed, four-pole operating state.
3. The method of claim 2 wherein the step of establishing the
operating state of the motor involves comparing the monitored
frequency or period of the companion alternator output to at least
one threshold frequency or period and establishing the pole state
based upon the comparison made.
4. The method of claim 3, further comprising the steps of:
providing a bypass path around the refrigerant compressor, the
bypass path including a flow control device positioned therealong;
halting motor operation for a time period prior to switching the
motor from one pole state to another pole state; and operating the
flow control device to permit flow along the bypass path during at
least part of the time period during which motor operation is
halted.
5. The method of claim 4 wherein the time period is between about 5
seconds and about 25 seconds.
6. The method of claim 5 wherein the time period is between about
10 seconds and about 20 seconds.
7. A locomotive cab air conditioning method, comprising: providing
a multi-speed motor operable in at least a first speed state and a
second speed state, the motor connected for driving a refrigerant
compressor from power derived from a companion alternator output;
monitoring an operating speed of a locomotive engine; and
establishing operation of the motor in one of the motor speed
states based at least in part upon the monitored locomotive engine
speed.
8. The method of claim 7 wherein the first speed state of the
multi-speed motor is a high speed, two-pole operating state and
wherein the second speed state of the multi-speed motor is a low
speed, four-pole operating state.
9. The method of claim 7 wherein the first speed state is a higher
speed state than the second speed state, the step of establishing
the speed state of the motor involves comparing the monitored
locomotive engine speed to at least one threshold speed, operating
the motor in the first speed state when the monitored locomotive
engine speed is below the threshold speed, and operating the motor
in the second speed state when the locomotive engine speed is above
the threshold.
10. The method of claim 9 wherein a hysteresis factor is provided
about the threshold speed in order to prevent repetitive switching
between the first speed state and the second speed state of the
motor when the locomotive engine is operating around the threshold
speed for an extended time period.
11. The method of claim 9 wherein the speed monitoring step
involves monitoring one of a frequency or period of the companion
alternator output.
12. The method of claim 7, further comprising the steps of:
providing a bypass path around the refrigerant compressor, the
bypass path including a flow control device positioned therealong;
halting motor operation for a time period prior to switching the
motor from one speed state to another speed state; and operating
the flow control device to permit flow along the bypass path during
at least part of the time period during which motor operation is
halted.
13. The method of claim 12 wherein the time period is between about
5 seconds and about 25 seconds.
14. The method of claim 13 wherein the time period is between about
10 seconds and about 20 seconds.
15. A locomotive cab air conditioning control system for use with a
locomotive cab air conditioning system including a compressor, a
condenser fan motor, an evaporator fan motor, and a companion
alternator associated with the locomotive engine for providing a
power output which varies in frequency as the locomotive engine
speed varies, the control system comprising: a detection circuit
for detecting a frequency or period of the companion alternator
power output; a controller for receiving a frequency or period
indicative output from the detection circuit; a multi-speed motor
for controlling operation of the compressor utilizing power from
the companion alternator power output; an inverter for providing
engine-speed-independent power to the condenser fan motor and to
the evaporator fan motor; a contactor control circuit connected to
a contact arrangement of the multi-speed motor for controlling a
contact/pole state thereof, the contactor control circuit
responsive to control signals received from the controller; and
wherein the controller is operable to monitor a frequency or period
of the companion alternator power output, and to provide an output
signal to the contactor control circuit for controlling operation
of the motor in one of at least two pole states based upon the
monitored frequency or period.
16. A locomotive cab air conditioning control system for use with a
locomotive cab air conditioning system including a compressor and a
companion alternator associated with the locomotive engine for
providing a power output which varies in frequency as the
locomotive engine speed varies, the control system comprising: a
detection circuit for detecting a frequency or period of the
companion alternator power output; a controller for receiving a
frequency or period indicative output from the detection circuit; a
multi-speed motor connected for controlling operation of the
compressor utilizing power from the companion alternator power
output; wherein the controller is connected to control a speed
state of the multi-speed motor, and wherein the controller is
operable to monitor a frequency or period of the companion
alternator power output and to establish a speed state of the
multi-speed motor based at least in part upon the monitored
frequency or period.
17. The control system of claim 16 further comprising an
opto-isolator circuit for connection between the companion
alternator power output and the detection circuit.
18. The control system of claim 16 comprising a contactor control
circuit connected to receive motor state control signals from the
controller and to control a pole state of the multi-speed motor in
response thereto.
19. The control system of claim 16 wherein the locomotive cab air
conditioning system includes a bypass path around the refrigerant
compressor, the bypass path including a flow control device
positioned therealong, wherein the controller is further operable
to (i) halt operation of the multi-speed motor for a time period
prior to switching the motor from one speed state to another speed
state, and (ii) operate the flow control device to permit flow
along the bypass path during at least part of the time period
during which motor operation is halted.
20. A locomotive cab air conditioning, comprising: a companion
alternator associated with the locomotive engine for providing a
power output which varies in frequency as the locomotive engine
speed varies; a multi-speed motor connected for controlling
operation of a compressor, the multi-speed motor connected to
receive the companion alternator power output; means for
establishing a contact/pole state of the multi-speed motor based at
least in part upon locomotive engine speed.
Description
[0001] This application claims the benefit of provisional
application Serial No. 60/182,084 filed Feb. 11, 2000.
TECHNICAL FIELD
[0002] The present invention relates generally to locomotive air
conditioners and, more particularly, to a locomotive air
conditioning control system providing improved operation over a
range of locomotive engine speeds.
BACKGROUND
[0003] Air conditioning (A/C) for the crew of diesel-electric
locomotives has been available in many different design concepts
for more than 15 years. These A/C systems are far different from
those found in commercial and residential applications because no
utility power source is available on freight locomotives to operate
them, i.e. there are no 110 volt or 220 volt single phase outlets;
there also are no 230 or 460 volt three phase outlets.
[0004] The supplier of an air conditioner for a locomotive cab must
operate his product from either or both of two power supplies on
the locomotive: 74 volts DC and/or a three-phase variable-voltage
and variable-frequency supply from the companion alternator, which
changes its output from 26.7 Hz, 44.5 volts AC to 120 Hz, 200 volts
AC, directly as engine speed changes from 200 to 900 RPM.
[0005] Early non-hermetic systems of the 74 volt DC type used three
DC motors to operate the compressor, evaporator fan motor and
condenser fan motor. These motors were extremely expensive and
required regular brush, commutator and DC contactor maintenance.
For these reasons, such systems have been unpopular.
[0006] In the 1990s, a hermetic, all - AC motor system was
introduced which used solid state inverters to convert 74 volts DC
to three-phase AC power to run the three air conditioning motors.
Today this technology dominates the locomotive A/C industry, and
accounts for almost 100% of all new locomotive (OEM) applications.
The appeal of this technology is clear:
[0007] (1) Hermetic--no shaft seal leakage
[0008] (2) No brushes--low maintenance and better reliability
[0009] (3) No contactors--improved reliability
[0010] (4) Solid state, microcomputer control--improved control
features.
[0011] The principal disadvantage of this technology is its cost.
While that cost level can be justified on new locomotives, it is
difficult to justify on a retrofit package for perhaps thousands of
older locomotives which need A/C to meet potential FRA rules and
workforce demands. In addition, the 74 volt DC electrical system of
these older locomotives may be inadequate for the additional A/C
load; upgrading the 74 volt DC system is an additional major
expense.
[0012] Systems of the companion alternator type were popular before
the introduction of 74 volt hermetic systems already described. One
short coming of these products was simply that A/C performance
changed as the locomotive was operated from idle to maximum speed.
In particular, since the companion alternator output frequency
changes from 120 Hz to 26.7 Hz as the engine changes its speed by
the ratio of 900 RPM to 200 RPM, or 4.5:1, the motor would have to
be selected such that at 120 Hz the compressor did not overspeed.
Clearly the compressor capacity would be reduced by about 4.5:1 (78
%) at locomotive idle. Similarly the air delivery of a condenser
fan would be reduced by the same amount. These two factors show
that indeed such single-speed systems must have poor A/C capacity
at idle. Since older locomotives are often used extensively in low
speed service, crew complaints of inadequate A/C capacity have been
common with this technology. Furthermore, the product uses a
shaft-driven (open drive) compressor and leaks, therefore, can
occur at the rotating shaft seal, compromising reliability.
SUMMARY
[0013] In one aspect, a locomotive cab air conditioning method
involves providing a multi-speed motor operable in at least a first
pole state and a second pole state, the motor connected for driving
a refrigerant compressor from power derived from a companion
alternator output of the locomotive. A frequency or period of the
companion alternator output is monitored, and operation of the
motor in one of the pole states is established based at least in
part upon the monitored frequency or period.
[0014] In another aspect, a locomotive cab air conditioning method
involves providing a multi-speed motor operable in at least a first
speed state and a second speed state, the motor connected for
driving a refrigerant compressor from a companion alternator output
of the locomotive. An operating speed of a locomotive engine is
monitored, and operation of the motor in one of the speed states is
established based at least in part upon the monitored locomotive
engine speed.
[0015] In still a further aspect, a locomotive cab air conditioning
control system for use with a locomotive cab air conditioning
system including a compressor and a companion alternator associated
with the locomotive engine for providing a power output which
varies in frequency as the locomotive engine speed varies is
provided. The control system includes a detection circuit for
detecting a frequency or period of the companion alternator power
output and a controller for receiving a frequency or period
indicative output from the detection circuit. A multi-speed motor
is connected for controlling operation of the compressor utilizing
power from the companion alternator power output. The controller is
connected to control a speed state of the multi-speed motor, and
the controller is operable to monitor a frequency or period of the
companion alternator power output and to establish a speed state of
the multi-speed motor based at least in part upon the monitored
frequency or period.
[0016] In still a further aspect, a locomotive cab air conditioning
control system for use with a locomotive cab air conditioning
system including a compressor, a condenser fan motor, an evaporator
fan motor, and a companion alternator associated with the
locomotive engine for providing a power output which varies in
frequency as the locomotive engine speed varies is provided. The
control system includes a detection circuit associated for
detecting a frequency or period of the companion alternator power
output and a controller for receiving a frequency or period
indicative output from the detection circuit. A multi-speed motor
is provided for controlling operation of the compressor utilizing
power from the companion alternator power output, and an inverter
for providing engine-speed-independent power to the condenser fan
motor and to the evaporator fan motor is included. A contactor
control circuit is connected to a contact arrangement of the
multi-speed motor for controlling a contact/pole state thereof, the
contactor control circuit responsive to control signals received
from the controller. The controller is operable to monitor a
frequency or period of the companion alternator power output, and
to provide an output signal to the contactor control circuit for
controlling operation of the motor in one of at least two pole
states based upon the monitored frequency or period.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a graph of compressor capacity vs. compressor
speed;
[0018] FIG. 2 is a graph of compressor capacity vs. locomotive
engine speed for a multi-speed compressor motor and a single speed
compressor motor, both powered by the variable output of a
companion alternator;
[0019] FIG. 3 is a graph of system capacity vs. locomotive engine
speed for a rooftop type system;
[0020] FIG. 4 is a schematic of one embodiment of an exemplary
refrigerant system;
[0021] FIG. 5 is a schematic of one embodiment of a control
arrangement for a locomotive cab A/C system;
[0022] FIG. 6 is a schematic of another embodiment of an exemplary
refrigerant system; and
[0023] FIG. 7 is a schematic of another embodiment of a control
arrangement for a locomotive cab A/C system.
DETAILED DESCRIPTION
[0024] Referring to the compressor capacity curves shown in FIGS.
1-3, the use of a multi-speed motor to operate the compressor of a
locomotive A/C system significantly improves A/C performance at low
engine speeds and can ensure that the compressor does not overspeed
at high engine speeds. The graph 100 of FIG. 1 shows compressor
capacity vs. compressor speed, the graph 110 of FIG. 2 shows
compressor capacity vs. locomotive engine rpm of a compressor
operated by a multi-speed motor and a compressor operated by a
single speed motor, and the graph 120 of FIG. 3 shows system
capacity vs. locomotive engine rpm for a rooftop type locomotive
A/C system.
[0025] In one embodiment, as will be described in further detail
below, the multi-speed motor operates by changing its number of
poles by connecting the consequent pole stator winding in delta
configuration for low speed operation and in wye configuration for
high speed.
[0026] Referring to FIG. 4, a schematic depiction of one embodiment
of a refrigerant system 10 is shown. The relative locations of the
condenser fan 12 and compressor 14 in such a system are shown. The
illustrated system 10 may be a locomotive cab rooftop
configuration, but could also be some other type of configuration
such as sub-base or side mount.
[0027] Referring to FIG. 5 one embodiment of a power and control
system arrangement 20 is depicted. The three-phase companion
alternator 22 generates variable frequency output AC power on lines
L1, L2, L3, with the frequency varying in proportion to the
locomotive engine speed (rpm). The companion alternator 22 is
inductively coupled via transformer arrangement 23 with a frequency
detector circuit 24 which provides a signal indicative of the
frequency or period of the companion alternator signal to a
controller 26. The companion alternator output is also provided
through a 3-phase bridge 28 to inverter 30, the bridge 28 providing
variable voltage DC to the inverter 30. The inverter 30 also
receives a control input in the form of a Hi/Lo speed command from
the controller 26. The inverter provides a 55 volt AC power signal
output to the evaporator fan 34 and the condenser fan 36,
regardless of the variable voltage DC, by varying a PWM signal to
account for the changing DC input. A contactor control circuit 38
is provided for controlling the operating state of the compressor
motor 39 based upon a control signal received from controller 26
via line 27. In particular, the number of operating poles of the
compressor motor 39 is changed by controlling the state of the
compressor motor control contacts 40, as will be explained in
further detail below with reference to FIG. 7. Power to switch the
compressor motor control contacts is also received from the output
of the controller 26 through the contactor control circuit 38 as
shown by line 42 but could be provided from another source. Power
for the electronic components such as controller 26, frequency
detector 24, and contactor control circuit 38 could be derived from
the companion alternator output or could also be derived from
another source such as the 74 volt DC supply commonly available in
locomotive applications.
[0028] The controller 26 also receives input data from a CRAT (cab
return air temperature) thermistor 44 and an OAT (outside air
temperature) thermistor 46. A heater interlock arrangement may also
be provided to the controller 26 to ensure that A/C does not
operate when heaters are energized. A control switch 48 provides an
input to the controller 26 for selecting any one of five operating
modes of the unit: OFF, LOW VENT, HIGH VENT, LOW COOL, and HIGH
COOL. An HPS (high pressure switch) 50 and an LPS (low pressure
switch) 52 provide discrete control signals in response to
refrigerant circuit pressure and are intended to halt A/C operation
respectively in the event of either excessively high or low system
pressure.
[0029] In one embodiment of operation, at engine speeds less than a
threshold speed in the range of about 300 to about 500 RPM (as
determined by controller 26 from detector circuit 24) the motor 39
is connected for high speed (2 pole) operation; and at engine
speeds above the threshold speed (as determined by controller 26
from detector circuit 24), the motor 39 is automatically connected
for low speed (4 pole) operation by the controller 26 according to
the output effected on line 27 to the contactor control circuit 38.
The threshold speed can be selected as desired for a given
implementation, and in some implementations might be outside the
specifically noted range.
[0030] Since the frequency of the companion alternator output
changes directly with locomotive engine speed, the period of the
output voltage changes inversely with engine speed. A timer in
controller 26 may monitor this period and cause appropriate
switching to occur as previously described. Each switch point may
be provided with a few RPM of hysteresis to ensure chatter-free
speed changes. For example, while a change from two-pole operation
to four-pole operation might occur at an established period of the
companion alternator 22 output (representative of the threshold
engine speed), a switch back to two-pole operation may be prevented
unless the period of the companion alternator 22 output signal
falls below the established period by a predetermined or threshold
amount in order to prevent rapid switching between motor states
when the locomotive is operating around the switching speed. It is
recognized that some other indicator of locomotive engine speed
could likewise be monitored to control the switching of the motor
states or speeds.
[0031] The inverter 30 can maintain a constant fan speed,
independent of engine speed, since it produces 55 VAC motor power
regardless of the engine speed.
[0032] The proposed system may use a shaft-driven (open drive)
compressor, similar in concept to those found in earlier
non-hermetic systems. Refrigerant leakage at the rotary shaft seal,
if a concern, can be mitigated by providing seal lubrication and
extra refrigerant. In particular, because air conditioners may set
unused for weeks or months on a locomotive, the shaft seal can dry
out in that time and cause refrigerant to leak. Logic can be built
into the controls to run the compressor for a few seconds every day
to keep the seal lubricated, thereby extending its useful life.
Further, even with such a regular seal lubrication scheme, it is
likely that the shaft seals will leak at some time. Such leakage
need not result in a immediate loss of performance if extra
refrigerant is carried in the system. A receiver 15 (FIG. 4)
connected immediately after the condenser coil accomplishes this
purpose and may improve A/C capacity in high ambient conditions.
These two measures may be used to extend the maintenance interval
of the AC system.
[0033] Referring now to FIG. 6, a schematic depiction of another
embodiment of a refrigerant system 200 is shown. The refrigerant
system 200 is substantially the same as system 10 of FIG. 4, with
the exception that a compressor bypass path 202 is provided having
a normally closed solenoid valve 204, or other flow control device,
positioned therealong. The bypass path 202 can be used to
substantially equalize compressor head pressure prior to changing
motor pole or speed states as will be described in more detail
below. Referring to FIG. 7, another embodiment of a power and
control system arrangement 220 is depicted. Like numerals reflect
similarities between system 220 and system 20 of FIG. 5. System 220
includes an opto-isolator arrangement 222 between the companion
alternator 22 and the frequency detector circuit 24, using diode
224 and light sensitive transistor 226, to provide electrical
isolation of the companion alternator output from the frequency
detector circuit 24. A 2 pole R-C filter 228 is also provided to
remove noise from the companion alternator output. LED 224 turns on
and off with a frequency which corresponds to the frequency of the
companion alternator output, and thus transistor 226 switches
between on and off states in a corresponding manner, enabling
circuit 24 to detect the frequency or period of the companion
alternator output.
[0034] The controller 26 of system 220 also includes an additional
output 230 which is used to control the solenoid valve 204 along
bypass path 202. In particular, the solenoid valve 204 may be
opened each time a transition between pole states of motor 39 is
made in order to reduce head pressure. For example, when it is
desired to switch from a 2 pole high speed state to a 4 pole low
speed state, or visa versa, operation of the compressor motor 39
may be halted for an established time period and the solenoid valve
204 may be opened during at least part of that time period in order
to substantially equalize the pressure. The compressor motor 39 can
then be started again in its new pole state. In one embodiment the
established time period may be between about 5 and about 25 seconds
while in another embodiment the time period may be between about 10
and about 20 seconds, but it is recognized that this time period
could vary from those ranges depending upon the particular
application or system. The solenoid valve 204 may be closed
immediately before restarting the compressor motor, simultaneous
with restarting the compressor motor, or after restarting the
compressor motor.
[0035] With respect to switching of the motor speed states, in the
illustrated embodiments compressor motor 39 comprises a single
winding motor which is controlled by changing its number of poles
by connecting the consequent pole stator winding in delta
configuration for low speed operation and in wye configuration for
high speed operation. In particular, referring to FIG. 7, the HI 1
contact controller controls HI contacts 230, the HI 2 contact
controller controls HI contacts 232, and the LO contact controller
controls contacts 234. Table 236 shows the manner in which the
contacts are controlled in order to achieve desired low speed and
high speed operation. It is recognized that other multi-speed motor
arrangements could be utilized.
[0036] Although the invention has been described above in detail
referencing the preferred embodiments thereof, it is recognized
that various changes and modifications could be made without
departing from the spirit and scope of the invention.
* * * * *