Note: Descriptions are shown in the official language in which they were submitted.
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MULTI-CAPACITY COMPRESSOR WITH
VARIABLE SPEED DRIVE AND METHOD OF USE
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Non-Provisional Patent
Application No. 16/272,085 filed on 11 February 2019, which is a continuation-
in-part
application of U.S. Patent Application No. 15/334,101, filed 25 October 2016,
the entire
contents and disclosure of which are hereby incorporated by reference in their
entirety.
BACKGROUND
[0002] The field of the disclosure relates generally to multi-capacity
compressors, and more specifically to a multi-capacity compressor with a
variable speed
drive.
[0003] Known multi-capacity compressors provide two or more levels
of compression, e.g., a two-capacity compressor provides a high and low
compression
level. Many known heating ventilation and cooling (HVAC) systems, such as, for
example, an air conditioner or a heat pump, utilize multi-capacity compressors
to provide
two levels of cooling capacity. One level, i.e., the high-capacity setting,
provides cooling
for hot, high-demand days. Another level, i.e., the low-capacity setting,
provides cooling,
for example, for milder days or other low-cooling demand periods of time. A
typical
installation utilizes the low-capacity setting 80% of the time, resulting in
improved
efficiency in operating the HVAC system. In such systems, the two-capacity
compressor
operates for longer periods of time, produces less noise, and produces more
even
temperatures. Accordingly, multi-capacity HVAC systems provide greater comfort
and
operate with greater efficiency.
[0004] A typical two-capacity HVAC system operates at 100% capacity
on the high-capacity setting and at about 66% capacity on the low-capacity
setting. Such
systems demonstrate an improved, i.e., higher, seasonal energy efficiency
ratio (SEER)
when operating at lower capacity. Efficiency improvements are gained in part
by more
efficient operation of the compressor, and also through operation of the
indoor and
outdoor fans at lower speeds. Typically, the system is more efficient at lower
compressor
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capacity. Efficiency improvements are typically limited in this regard, in
that the two-
capacity compressor cannot operate at a low enough capacity to match the
cooling load
or achieve the efficiencies of fully variable speed systems.
BRIEF DESCRIPTION
[0005] In one aspect, a heating ventilation and air conditioning (HVAC)
system is provided. The HVAC system includes a multi-capacity compressor
configured
to operate selectively at a high-capacity setting, a medium-capacity setting,
and a low-
capacity setting to provide a compressor output. The HVAC system also includes
a
variable-voltage variable-frequency drive coupled to the multi-capacity
compressor and
configured to operate the multi-capacity compressor at a variable speed, and a
processor
coupled to the multi-capacity compressor and the variable-voltage variable-
frequency
drive. The processor is configured to select one of the high-capacity setting,
the medium-
capacity setting, or the low capacity setting at which the multi-capacity
compressor
should operate based on a load determined for the multi-capacity compressor.
The
processor is also configured to employ the variable-voltage variable-frequency
drive to
operate the multi-capacity compressor at the variable speed to match the
compressor
output to the load, and bypass the variable-voltage variable-frequency drive
when
operating the multi-capacity compressor at the high-capacity setting for a
compressor
heating output based on a heating load.
[0006] In another aspect, a control system for a multi-capacity
compressor is provided. The control system includes an alternating current
(AC) line
voltage source configured to operate the multi-capacity compressor, a variable-
voltage
variable-frequency drive coupled to the AC line voltage source and configured
to operate
the multi-capacity compressor at a variable speed, and a processor coupled to
the AC line
voltage source and the variable-voltage variable-frequency drive. The
processor is
configured to selectively couple the AC line voltage source and the variable-
voltage
variable-frequency drive to the multi-capacity compressor to operate the multi-
capacity
compressor. The processor is also configured to transmit a capacity control
signal to the
multi-capacity compressor, the control signal instructive to operate the multi-
capacity
compressor in one of a high-capacity setting, a medium-capacity setting, or a
low-
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capacity setting, while the multi-capacity compressor is being powered by the
selectively
coupled one of the AC line voltage source or the variable-voltage variable-
frequency
drive.
[0007] In yet another aspect, a control system for a multi-capacity
compressor configured to operate in at least two capacity settings is
provided. The
control system includes an alternating current (AC) line voltage source
configured to
operate the multi-capacity compressor, a variable-voltage variable-frequency
drive
coupled to the AC line voltage source and configured to operate the multi-
capacity
compressor at a variable speed, and a processor coupled to the AC line voltage
source
and the variable-voltage variable-frequency drive. The processor is configured
to
selectively couple the AC line voltage source and the variable-voltage
variable-frequency
drive to the multi-capacity compressor to operate the multi-capacity
compressor. The
processor is also configured to transmit a capacity control signal to the
multi-capacity
compressor, the control signal configured to select one of the at least two
capacity
settings at which the multi-capacity compressor is to operate while the multi-
capacity
compressor is being powered by the selectively coupled one of the AC line
voltage
source or the variable-voltage variable-frequency drive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a block diagram of an exemplary HVAC system;
[0009] FIG. 2 is a schematic diagram of one embodiment of a control
system for use in the HVAC system shown in FIG. 1;
[0010] FIG. 3 is a flow diagram of an exemplary method of operating a
multi-capacity compressor, such as the multi-capacity compressor shown in FIG.
1; and
[0011] FIG. 4 is a flow diagram of another exemplary method of
operating a multi-capacity compressor, such as the multi-capacity compressor
shown in
FIG. 1.
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DETAILED DESCRIPTION
[0012] As used herein, an element or step recited in the singular and
preceded with the word "a" or "an" should be understood as not excluding
plural
elements or steps, unless such exclusion is explicitly recited. Furthermore,
references to
"example implementation" or "one implementation" of the present disclosure are
not
intended to be interpreted as excluding the existence of additional
implementations that
also incorporate the recited features.
[0013] Single-capacity and multi-capacity, such as, for example, and
without limitation, two-capacity HVAC systems generally cannot vary the speed
of the
compressor. Although two-capacity compressors can operate at a lower capacity,
e.g.,
66%, the lower capacity is typically not as low as is achieved in variable
speed
compressors. Consequently, such systems cannot match the cooling load during
mild
conditions, resulting in shortened operating periods, frequent cycling, and
greater
temperature variations. Variable speed HVAC systems are typically more complex
due
to the necessary electronics to match the drive speed to the cooling load, but
do provide
more efficient and more comfortable cooling over a wider range of cooling
loads.
Cooling loads, in certain embodiments, may be measured or estimated.
[0014] Embodiments of the present disclosure, it is realized herein,
provide a combination of a multi-stage compressor (referred to herein as a
"multi-
capacity" compressor) and a variable speed drive that provide an even greater
range of
efficient operation and further improve SEER, in some cases, for example, in
excess of 5
SEER. More specifically, embodiments of the HVAC systems described herein may
utilize a multi-capacity compressor in combination with a variable-voltage
variable-
frequency drive. It is further realized herein that such an HVAC system may be
operated
in various configurations, including at high-capacity with the variable-
voltage variable-
frequency drive, at low-capacity with the variable-voltage variable-frequency
drive, at
high-capacity with alternating current (AC) line voltage, and at low-capacity
with AC
line voltage. More specifically, as realized herein, in certain embodiments,
operation of
the multi-capacity compressor at high-capacity with AC line voltage provides a
high-
capacity setting, operation at low-capacity with AC line voltage provides a
medium-
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capacity setting, and operation at low-capacity with the variable-voltage
variable-
frequency drive provides a range of low-capacity settings varying in speed. It
is further
realized herein that, by foregoing operation at high-capacity with the
variable-voltage
variable-frequency drive, a lower-rated variable-voltage variable-frequency
drive may be
utilized. It is further realized herein that bypassing the variable-voltage
variable-
frequency drive for the high-capacity setting and the medium-capacity setting
further
improves efficiency by eliminating operating losses of the variable-voltage
variable-
frequency drive.
[0015] In some embodiments, the HVAC system may be operated in
various other configurations, including at a medium-capacity with the variable-
voltage
variable-frequency drive and at medium-capacity with AC line voltage, wherein
the
medium-capacity represents a capacity level between the high-capacity and low-
capacity.
It is further realized that one or more capacity levels of the compressor may
be
associated with a heating operation of the HVAC system. In one particular
embodiment,
the high-capacity levels is associated with a heating operation of the HVAC
system ¨
that is, when the compressor operates under the high-capacity setting, the
HVAC system
is operating as a heat pump to heat an interior space.
[0016] As used herein, a "capacity" of the multi-capacity compressor
refers to a cooling (or heating) capacity, and is variable (e.g., between high-
capacity,
medium-capacity, and low-capacity) by varying an internal volume of the multi-
capacity
compressor. For example, an actuator may be operated to vary the volume from a
full
internal volume, at which the multi-capacity compressor is operated at high-
capacity, to a
reduced internal volume, at which the multi-capacity compressor is operated at
low-
capacity or medium-capacity. Additional actuators and/or variably operable
actuators
may provide additional variability of the internal volume to provide
additional capacity
levels at which the multi-capacity compressor may operate. Where "cooling
capacity"
and/or "cooling load" are referred to herein, it should be understood that
such
descriptions may be equally applicable to the "heating capacity" and/or
"heating load" of
the HVAC system.
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[0017] FIG. 1 is a block diagram of an exemplary HVAC system 100.
HVAC system 100 includes a compressor 102 that compresses a refrigerant 104 to
produce a pressure within HVAC system 100 and a resulting flow of refrigerant
104.
Compressor 102 is a two-capacity compressor having two distinct levels of
capacity at
which compressor 102 may operate. In alternative embodiments, compressor 102
may
have 3 or more levels of capacity. The levels of capacity are referred to as a
high-
capacity setting and a low-capacity setting, which further refer to the
cooling capacity
available at the respective levels of capacity. Generally, compressor 102
consumes more
energy, i.e., electrical power, and is less efficient when operating at the
high-capacity
setting versus the low-capacity setting. A typical installation of HVAC system
100
operates compressor 102 at the low-capacity setting about 80% of its operating
time.
[0018] As described above, in other embodiments, compressor 102 is a
three-capacity compressor having three distinct levels of capacity at which
compressor
102 may operate. The levels of capacity are referred to as a high-capacity
setting, a
medium-capacity setting, and a low-capacity setting, which further refer to
the cooling or
heating capacity available at the respective levels of capacity (e.g., based
on the internal
volume of compressor 102 at the respective levels of capacity).
[0019] HVAC system 100 includes an outdoor heat exchanger 106, an
indoor heat exchanger 108, and an expansion valve 110. Compressor 102
generates the
flow of refrigerant 104 through each of outdoor heat exchanger 106, indoor
heat
exchanger 108, and expansion valve 110 to cool an interior space 112. Heat
from interior
space 112 is carried by refrigerant 104 and transferred to an exterior space
114. Interior
space 112 and exterior space 114 combine to define a cooling load for HVAC
system
100 as a function of a temperature set point for interior space 112 and an
ambient
temperature of exterior space 114. When operating as a heat pump, HVAC system
100
operates in reverse, carrying heat from exterior space 114 into interior space
112.
Accordingly, where reference is made herein to cooling interior space 112, it
should be
understood that HVAC system 100 is also configured to heat interior space 112,
and such
descriptions should be considered non-limiting.
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[0020] During operation, as cool low-pressure refrigerant 104 moves
through indoor heat exchanger 108, a blower 116 generates an interior airflow
118
through indoor heat exchanger 108. Interior airflow 118 carries warm air from
interior
space 112 through indoor heat exchanger 108, thereby cooling interior airflow
118 and
heating refrigerant 104. Low-pressure refrigerant 104 flows from indoor heat
exchanger
108 into compressor 102 and is compressed, raising the temperature and
pressure of
refrigerant 104 before it flows into outdoor heat exchanger 106. HVAC system
100
includes a fan 120 that generates an exterior airflow 122 through outdoor heat
exchanger
106. As hot high-pressure refrigerant 104 moves through outdoor heat exchanger
106,
exterior airflow 122 carriers ambient air from exterior space 114 through
outdoor heat
exchanger 106, thereby cooling refrigerant 104 and heating exterior airflow
122. High-
pressure refrigerant 104 flows from outdoor heat exchanger 106 into expansion
valve
110, where refrigerant 104 is decompressed and cooled before flowing back into
indoor
heat exchanger 108.
[0021] HVAC system 100 also includes a variable speed drive 124
coupled to blower 116 and configured to turn blower 116 at a variable speed.
The speed
at which blower 116 turns determines the volume of air in interior airflow 118
that
moves through indoor heat exchanger 108. Moreover, the efficiency with which
energy
is transferred from the warm interior airflow 118 to the cool low-pressure
refrigerant 104
flowing through indoor heat exchanger 108 is a function of the volume of air
and the
speed at which blower 116 turns. Further, the speed of blower 116 that is
necessary to
achieve efficient energy transfer may be reduced as the cooling load
decreases. The
speed of blower 116 may be further decreases when compressor 102 is operated
at low-
capacity.
[0022] HVAC system 100 includes a variable speed drive 126 coupled
to fan 120 and configured to turn fan 120 at a variable speed. The speed at
which fan 120
turns determines the volume of air in exterior airflow 122 that moves through
outdoor
heat exchanger 108. Moreover, the efficiency with which energy is transferred
from the
warm high-pressure refrigerant 104 flowing through outdoor heat exchanger 106
to
exterior airflow 122 is a function of the volume of air and the speed at which
fan 120
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turns. Further, the speed of fan 120 that is necessary to achieve efficient
energy transfer
may be reduced as the cooling load decreases. The speed of fan 120 may be
further
decreased when compressor 102 is operated at low-capacity.
[0023] HVAC system 100 includes a variable-voltage variable-
frequency drive 128 coupled to compressor 102. Variable-voltage variable-
frequency
drive 128 provides power to compressor 102 and regulates an output voltage and
frequency to control the speed at which compressor 102 operates, thereby
affecting the
overall cooling capacity of compressor 102. At lower speeds, compressor 102
operates at
a lower cooling capacity. At higher speeds, compressor 102 operates at a
higher cooling
capacity. Compressor 102 may be combined with variable-voltage variable-
frequency
drive 128 in various manners, including operating at a variable speed at the
high-capacity
setting, and operating at a variable speed at the low-capacity setting.
Further, compressor
102 may be operated at AC line voltage to achieve respective maximum cooling
capacities at the high-capacity setting and the low-capacity setting. More
specifically,
when operating compressor 102 at AC line voltage, variable-voltage variable-
frequency
drive 128 is bypassed, thereby eliminating the operating losses introduced by
variable-
voltage variable-frequency drive 128.
[0024] Compressor 102 may also be operated at a variable speed at a
medium-capacity setting with either variable-voltage variable-frequency drive
128 or AC
line voltage, thereby increasing the range of operation of HVAC system 100.
[0025] FIG. 2 is a block diagram of an exemplary control system 200
for use with HVAC system 100 shown in FIG. 1 and, more specifically,
compressor 102.
Control system 200 includes an AC line voltage source 202 and variable-voltage
variable-frequency drive 128 that are alternatively coupled to compressor 102
through a
switching network 204 to operate compressor 102. For example, AC line voltage
source
202 is coupled to compressor 102 through a run capacitor 214 and directly by
closing
corresponding switches within switching network 204 and decoupling variable-
voltage
variable-frequency drive 128. Similarly, AC line voltage source 202 is
decoupled from
compressor 102 by opening corresponding switches within switching network 204,
coupling variable-voltage variable-frequency drive 128 to compressor 102, and
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bypassing run capacitor 214. In alternative embodiments, AC line voltage
source 202
and variable-voltage variable-frequency drive 128 may be alternatively coupled
and
decoupled from compressor 102 using any suitable switching device or network
of
switching devices, including, for example, and without limitation,
electromechanical
relays, field effect transistor (FET) devices, insulated-gate bipolar
transistors (IGBTs),
and other power electronics. AC line voltage source 202 provides an AC line
voltage
signal, such as, for example 60 Hertz 240 Volt. In alternative embodiments, AC
line
voltage source 202 may provide other frequencies and voltages according to the
grid
requirements for that particular implementation. For example, certain
countries utilize 50
Hertz as a line frequency. Similarly, certain countries utilize 230 Volt as a
line voltage.
AC line voltage source 202 may include a terminal block or bus configured to
provide
line voltage. In certain embodiments, AC line voltage source 202 may include a
main
system relay configured to switch AC line voltage to compressor 102, HVAC
system
100, or both, for example.
[0026] Control system 200 includes a processor 208. Processor 208 is
coupled to switching network 204. Processor 208 controls switching network 204
to
alternatively couple AC line voltage source 202 and variable-voltage variable-
frequency
drive 128 to compressor 102. Processor 208 is further coupled to variable-
voltage
variable-frequency drive 128 to control the speed at which compressor 102 is
operated
when operated by variable-voltage variable-frequency drive 128. Processor 208
transmits
a speed control signal 210 to variable-voltage variable-frequency drive 128 to
affect the
speed at which compressor 102 is operated. Speed control signal 210 received
by
variable-voltage variable-frequency drive 128 is instructive to operate
compressor 102 at
a variable speed. Processor 208 is further coupled to compressor 102.
Processor 208
transmits a capacity control signal 212 to compressor 102. Capacity control
signal 212,
when received by compressor 102, is instructive to operate compressor 102 at
either a
high-capacity setting or a low-capacity setting. In certain embodiments,
processor 208 is
integrated with variable-voltage variable-frequency drive 128.
[0027] In some embodiments, processor 208 transmits capacity control
signal 212 to instruct compressor 102 to operate in one of the high-capacity
setting, a
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medium-capacity setting, and the low-capacity setting. That is, compressor 102
operates
in only one of the capacity settings at any one time. Accordingly, in various
embodiments, processor 208 transmits capacity controls signal 212 over one or
more
analog signal lines, or over a digital signal line.
[0028] In certain embodiments, processor 208 is configured to couple
AC line voltage source 202 to compressor 102 and bypass variable-voltage
variable-
frequency drive 128, thereby eliminating the operating losses introduced by
variable-
voltage variable-frequency drive 128.
[0029] FIG. 3 is a flow diagram of an exemplary method 300 of
operating compressor 102, shown in FIGs. 1 and 2. Method 300 begins at a start
step
310. Processor 208 determines a cooling load for compressor 102 at a
determination step
320. The cooling load is determined as a function of a temperature set point
for interior
space 112 and an ambient temperature for exterior space 114.
[0030] At a capacity selection step 330, processor 208 selects a cooling
capacity setting based on the determined cooling load. The cooling capacity
setting is
selected from among the high-capacity setting and the low-capacity setting for
compressor 102. Generally, processor 208 selects the high-capacity setting
when the
cooling load is large, and selects the low-capacity setting when the cooling
load is
smaller.
[0031] Processor 208 transmits a capacity control signal 212 to
compressor 102 at a capacity control step 340. Capacity control signal 212 is
instructive
to operate compressor 102 at the selected cooling capacity setting, i.e., the
high-capacity
setting or the low-capacity setting.
[0032] At a power source selection step 350, processor 208 selects a
power source to operate compressor 102 based on the determined cooling load.
The
power source is selected by processor 208 from among AC line voltage source
202 and
variable-voltage variable-frequency drive 128. Given the capacity selection at
capacity
selection step 330 and the determined cooling load, processor 208 selects
either AC line
voltage source 202 or variable-voltage variable-frequency drive 128 to match
the cooling
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output of compressor 102 during operation 360 of compressor 102 with the
determined
cooling load. For example, when the cooling load is at its maximum, processor
208
selects 330 the high-capacity setting for compressor 102 and operates 360
compressor
102 with AC line voltage source 202 as the power source to produce the maximum
cooling output. Likewise, when the cooling load is minimal, processor 208
selects 330
the low-capacity setting and operates 360 compressor 102 using variable-
voltage
variable-frequency drive 128 to achieve a low speed and low cooling output,
thereby
improving the efficiency of compressor 102. Further, when the cooling load is
at an
intermediate level, in certain embodiments, processor 208 selects 330 the low-
capacity
setting and further selects 350 AC line voltage source 202 to operate 360
compressor 102
at the maximum cooling capacity for the low-capacity setting. Moreover, in
such
embodiments, variable-voltage variable-frequency drive 128 is bypassed to
eliminate the
operating losses introduced by variable-voltage variable-frequency drive 128
when
operated at a variable speed.
[0033] In certain embodiments, compressor 102 is only operable with
variable-voltage variable-frequency drive 128 when compressor 102 is operated
at the
low-capacity setting. Consequently, when processor 208 selects 330 the high-
capacity
setting, processor 208 further selects 350 AC line voltage source 202 to
operate 360
compressor 102. Method 300 terminates at an end step 370.
[0034] FIG. 4 is a flow diagram of an exemplary method 400 of
operating compressor 102, shown in FIGs. 1 and 2. Method 400 begins at a start
step
410. Processor 208 determines one of a cooling load or a heating load
(generally, a load)
for compressor 102 at a determination step 420. The cooling load or heating
load for
compressor 102 is determined as a function of a temperature set point for
interior space
112 and an ambient temperature for exterior space 114.
[0035] At a capacity selection step 430, processor 208 selects a capacity
setting based on the determined cooling or heating load. The capacity setting
may be a
cooling capacity setting or a heating capacity setting. The capacity setting
is selected
from among the high-capacity setting, the medium-capacity setting, and the low-
capacity
setting for compressor 102 such that a compressor output (e.g., a heating or
cooling
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output from compressor 102) is matched to the determined load. Generally,
processor
208 selects the high-capacity setting when the cooling load is large, and
selects the
medium-capacity or low-capacity setting when the cooling load is smaller. For
example,
processor 208 selects the high-capacity setting when the cooling load is above
a first
threshold, selects the medium-capacity setting when the cooling load is below
the first
threshold and above a second (lower) threshold, and selects the low capacity
setting
when the cooling load is below the second threshold. In some embodiments, when
processor 208 determined a heating load for compressor 102, of any magnitude,
processor 208 selects the high-capacity setting. That is, in such embodiments,
the high-
capacity setting is reserved for heating operations of HVAC system 100.
[0036] Processor 208 transmits a capacity control signal 212 to
compressor 102 at a capacity control step 440. Capacity control signal 212 is
instructive
to operate compressor 102 at the selected capacity setting, i.e., the high-
capacity setting,
the medium-capacity setting, or the low-capacity setting.
[0037] At a power source selection step 450, processor 208 selects a
power source to operate compressor 102 based on the determined cooling or
heating
load. The power source is selected by processor 208 from among AC line voltage
source
202 and variable-voltage variable-frequency drive 128. Given the capacity
selection at
capacity selection step 430 and the determined cooling or heating load,
processor 208
selects either AC line voltage source 202 or variable-voltage variable-
frequency drive
128 to match a necessary output of compressor 102 during operation 360 of
compressor
102 with the determined cooling or heating load. For example, when a cooling
load is at
its maximum, processor 208 selects 430 the high-capacity setting for
compressor 102 and
operates 460 compressor 102 with AC line voltage source 202 as the power
source to
produce the maximum cooling output. Likewise, when the cooling load is
minimal,
processor 208 selects 430 the low-capacity setting and operates 460 compressor
102
using variable-voltage variable-frequency drive 128 to achieve a low speed and
low
cooling output, thereby improving the efficiency of compressor 102. Further,
when the
cooling load is at an intermediate level, in certain embodiments, processor
208 selects
430 the medium-capacity setting or the low-capacity setting and further
selects 450 AC
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line voltage source 202 to operate 460 compressor 102. Moreover, in such
embodiments,
variable-voltage variable-frequency drive 128 is bypassed to eliminate the
operating
losses introduced by variable-voltage variable-frequency drive 128 when
operated at a
variable speed. Method 400 terminates at an end step 470.
[0038] HVAC systems described herein provide a combination of a
multi-capacity compressor and a variable speed drive that provide an even
greater range
of efficient operation and further improve SEER, in some cases, for example,
in excess
of 5 SEER. More specifically, embodiments of the HVAC systems described herein
may
utilize a multi-capacity compressor in combination with a variable-voltage
variable-
frequency drive. It is further realized herein that such an HVAC system may be
operated
in various configurations, including at high-capacity with the variable-
voltage variable
frequency drive, at low-capacity with the variable-voltage variable-frequency
drive, at
high-capacity with alternating current (AC) line voltage, and at low-capacity
with AC
line voltage. More specifically, as realized herein, in certain embodiments,
operation of
the multi-capacity compressor at high-capacity with AC line voltage provides a
high-
capacity setting, operation at low-capacity with AC line voltage provides a
medium-
capacity setting, and operation at low-capacity with the variable-voltage
variable-
frequency drive provides a range of low-capacity settings varying in speed. It
is further
realized herein that, by foregoing operation at high-capacity with the
variable-voltage
variable-frequency drive, a lower-rated variable-voltage variable-frequency
drive may be
utilized. It is further realized herein that bypassing the variable-voltage
variable-
frequency drive for the high-capacity setting and the medium-capacity setting
further
improves efficiency by eliminating forward operating losses of the variable-
voltage
variable-frequency drive.
[0039] It is further realized that such an HVAC system may be operated
at medium-capacity with the variable-voltage variable frequency drive, and at
medium-
capacity with the AC line voltage. In certain embodiments, operation of the
multi-
capacity compressor at high-capacity is reserved for heating outputs based on
heating
loads, whereas operation of the multi-capacity compressor under lower-capacity
settings
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(e.g., low-capacity or medium-capacity) is reserved for cooling outputs
matched to
measured cooling loads.
[0040] The methods and systems described herein may be implemented
using computer programming or engineering techniques including computer
software,
firmware, hardware or any combination or subset thereof, wherein the technical
effect
may include at least one of: (a) combining a multi-capacity compressor with a
variable
speed drive, e.g., a variable-voltage variable-frequency drive; (b) reducing
losses by
bypassing the variable-voltage variable-frequency drive when operating at a
line voltage,
particularly at intermediate operating speeds; (c) operating the multi-
capacity compressor
at a low-capacity and at a variable speed; (d) operating a two-capacity
compressor at less
than 40% of full cooling capacity; (e) improving operating efficiency, e.g.,
SEER, of the
multi-capacity compressor and the HVAC system; (0 reducing the necessary fan
speeds
for heat transfer from heat exchangers during low cooling loads; (g) improving
efficiency
of the HVAC system further by lowering fan speeds to operate in a more
efficient range
of speeds; (h) operating the multi-capacity compressor at a low-capacity for
longer
cycles; (i) improving efficiency and comfort due to more continuous low-
capacity
cooling; (j) improving compressor lubrication through use at higher rotational
speed and
lower capacity; (k) reducing cost and complexity over variable speed
compressors; (1)
operating the multi-capacity compressor at three or more capacity levels,
including a
high-capacity, medium-capacity, and low-capacity; and (m) operating the multi-
capacity
compressor at a high-capacity setting under a heating load.
[0041] Some embodiments involve the use of one or more electronic or
computing devices. Such devices typically include a processor, processing
device, or
controller, such as a general purpose central processing unit (CPU), a
graphics
processing unit (GPU), a microcontroller, a reduced instruction set computer
(RISC)
processor, an application specific integrated circuit (ASIC), a programmable
logic circuit
(PLC), a field programmable gate array (FPGA), a digital signal processing
(DSP)
device, and/or any other circuit or processing device capable of executing the
functions
described herein. The methods described herein may be encoded as executable
instructions embodied in a computer readable medium, including, without
limitation, a
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storage device and/or a memory device. Such instructions, when executed by a
processing device, cause the processing device to perform at least a portion
of the
methods described herein. The above examples are exemplary only, and thus are
not
intended to limit in any way the definition and/or meaning of the terms
processor,
processing device, and controller.
[0042] In the embodiments described herein, memory may include, but
is not limited to, a computer-readable medium, such as a random access memory
(RAM),
and a computer-readable non-volatile medium, such as flash memory.
Alternatively, a
floppy disk, a compact disc ¨ read only memory (CD-ROM), a magneto-optical
disk
(MOD), and/or a digital versatile disc (DVD) may also be used. Also, in the
embodiments described herein, additional input channels may be, but are not
limited to,
computer peripherals associated with an operator interface such as a mouse and
a
keyboard. Alternatively, other computer peripherals may also be used that may
include,
for example, but not be limited to, a scanner. Furthermore, in the exemplary
embodiment, additional output channels may include, but not be limited to, an
operator
interface monitor.
[0043] As used herein, the terms "software" and "firmware" are
interchangeable, and include any computer program stored in memory for
execution by a
processor, including RAM memory, ROM memory, EPROM memory, EEPROM
memory, and non-volatile RAM (NVRAM) memory. The above memory types are
examples only, and are thus not limiting as to the types of memory usable for
storage of
a computer program.
[0044] The systems and methods described herein are not limited to the
specific embodiments described herein, but rather, components of the systems
and/or
steps of the methods may be utilized independently and separately from other
components and/or steps described herein.
[0045] This written description uses examples to provide details on the
disclosure, including the best mode, and also to enable any person skilled in
the art to
practice the disclosure, including making and using any devices or systems and
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16
performing any incorporated methods. The patentable scope of the disclosure is
defined
by the claims, and may include other examples that occur to those skilled in
the art.
Such other examples are intended to be within the scope of the claims if they
have
structural elements that do not differ from the literal language of the
claims, or if they
include equivalent structural elements with insubstantial differences from the
literal
language of the claims.
