`

`5,410,230
`
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`4,672,816 6/1987 Takahashi ............................. 62/180
`4,682,473 7/1987 Rogers, III ............................. 62/89
`4,688,547 8/1987 Ballard et al ................... 126/116 A
`4,710,691 12/1987 Bergstrom et al .................. 318/696
`4,712,050 12/1987 Nagasawa et al ................... 318/254
`4,722,018 1/1988 Pohl ...................................... 361/29
`4,736,143 4/1988 Nakamura et al .................. 318/432
`4,743,815 5/1988 Gee et al ............................. 318/254
`4,763,425 8/1988 Grennan ................................. 34/48
`4,773,587 9/1988 Lipman ................................. 236/11
`4,806,833 2/1989 Young ................................. 318/335
`4,829,221 5/1989 Grunberg et al ................... 318/587
`
`4,845,418 7/1989 Conner ................................ 318/778
`4,860,231 8/1989 Ballard et al ....................... 364/571
`4,860,552 8/1989 Beckey .................................. 62/158
`4,868,467 9/1989 Davis .................................. 318/254
`4,872,123 10/1989 Morita ................................. 364/571
`4,879,502 11/1989 Endo et al ........................... 318/808
`4,902,952 2/1990 Lavery ................................ 318/645
`4,939,437 7/1990 Farag et al. ......................... 318/473
`4,941,325 7/1990 Nuding .................................. 62/158
`4,950,918 8/1990 O'Breartuin et al ................ 307/242
`4,992,715 2/1991 Nakamura et al .............. 318/432 X
`5,107,685 4/1992 Kobayashi .......................... 318/807
`5,119,071 6/1992 Takezawa ........................... 318/811
`5,129,234 7/1992 Alford ................................ 62/176.6
`5,197,375 3/1993 Rosenbrock et al. 7 .•....•••.••.• 364/557
`
`2
`
`

`

`

`

`

`

`202 ~1
`CONVENTIONAL
`THERMOSTAT
`
`"'-!-STAT
`SIGNAL
`
`POWER
`SUPPLY
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`4
`~31
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`,-310
`J
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`302
`308
`~----~A~/D~----~~
`fl 1 E C M
`Ml CROPROCESSO R
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`t SPEED
`3q41
`30~
`,....----'-----..
`BEMF
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`,
`jROM ! PNVM , _ _,..TO ANTICIPATOR
`
`I
`
`r------------1
`I COMPRESSOR
`I
`I
`I
`::j BLOWER
`~. ~::
`1
`I FAN
`I
`~ 2
`I
`I
`I DRAFT INDUCER
`I
`L ___________ J
`
`316
`
`300
`
`FIG_3
`
`~ • 00. •
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`~
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`... cn
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`~ Ul
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`~
`m.
`a,
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`Ul
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`(I)
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`~ ..... = ~ =
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`5
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`

`5,410,230
`
`1
`
`VARIABLE SPEED HV AC WITHOUT
`CONTROLLER AND RESPONSIVE TO A
`CONVENTIONAL THERMOSTAT
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`This application is a continuation-in-part of copend(cid:173)
`ing application Ser. No. 07/889,708, filed May 27, 1992, 10
`the entire disclosure of which is incorporated herein by
`reference.
`
`BACKGROUND OF THE INVENTION
`This invention relates to temperature and/or humid- 15
`ity conditioning systems generally, and more particu(cid:173)
`larly to heating, air conditioning and ventilating systems
`and, with even more particularity, to systems having
`variable speed operation which is responsive to a two
`state temperature signal as provided, for example, by a 20
`thermostat.
`Variable capacity central heating, ventilating and air
`conditioning (HV A C) systems are typically controlled
`by electronic thermostats containing microprocessors
`which continuously monitor indoor air temperature by 25
`a thermistor or other means. The thermostat tempera(cid:173)
`ture set point is compared to the sensed or monitored
`temperature value and the microprocessor in the ther(cid:173)
`mostat evaluates this differential to generate a control 30
`signal. It should be apparent that it would be desirable
`to provide a system which eliminates the need for a
`microprocessor within a thermostat or as part of a sys(cid:173)
`tem controller. It would also be desirable that such an
`improved system (or parts thereof) be generally useable 35
`for controlling the humidity or temperature of air gen(cid:173)
`erally.
`Some HV AC systems have utilized sequencing of the
`outdoor fan motor, compressor, and indoor blower to
`maximize efficiency on start up and shut down (See, for 40
`example, U.S. Pat. No. 4,941,325). Alternatively, some
`systems delay operation of various components in an
`effort to improve air delivery temperature (See, for
`example, U.S. Pat. No. 4,860,552). However, these sys(cid:173)
`tems do not respond to environment changes and can- 45
`not be programmed to permit variable sequencing or
`delays depending on the temperature signal generated
`by a conventional thermostat.
`Further, present system applications require that the
`starting torque and/or speed-torque characteristics of 50
`the motors be predictable and repeatable. In addition, it
`is desirable that motors be operable at the highest rea(cid:173)
`sonably achievable efficiency consistent with mass pro(cid:173)
`duction techniques. Known present variable speed mo- 55
`tors cannot easily achieve this advantage because it has
`traditionally been impractical or too costly to minimize
`the variable effect on motor characteristics caused by
`manufacturing tolerances of the internal components of
`the motor. Present concepts and arrangements for ad- 60
`justing a motor for different applications require circuit
`changes such as multiple variable resistors in the elec(cid:173)
`tronic control for the motor or permanent software
`changes in an electronic control microprocessor. Both
`of the aforementioned arrangements are disadvanta- 65
`geous because they require a unique model to be built
`for calibrating a system which cannot be easily changed
`and can be quite expensive.
`
`2
`SUMMARY OF THE INVENTION
`It is an object of this invention to provide a central
`heating, air conditioning and ventilating system which
`5 does not require a system controller.
`It is still another object of this invention to provide a
`central heating, air conditioning and ventilating system
`which is responsive to a cyclic parameter of a tempera(cid:173)
`ture signal generated by a conventional thermostat
`which (toes require a microprocessor.
`It is still another object of this invention to provide a
`central heating, air conditioning and ventilating system
`wherein each motor of the system is independently
`controlled by a microprocessor integral with the mo(cid:173)
`tor/motor control.
`Another object of the invention is to provide a system
`which permits optimum airflow for maximum comfort
`and/ or efficiency for varied system environments.
`It is yet another object of this invention to provide a
`system which permits calibrating a motor control to
`actual characteristics or operating parameters of a
`motor while driving a known load.
`Yet another object is to provide a system which per(cid:173)
`mits calibrating the motor to a known load.
`A still further object is to provide a system which
`permits calibrating a motor control to motor character(cid:173)
`istics under a no load condition.
`Yet other objects of the present invention are to pro(cid:173)
`vide new and improved control techniques which may
`be applied to local air conditioning or heating units,
`refrigeration units, and humidity controlling units,
`whereby the above-stated objects may be carried out in
`applications other than central HV AC applications.
`In one form, a system embodying the invention com(cid:173)
`prises a system for conditioning air in a space by heating
`or cooling the air to change its temperature. Means,
`responsive to the temperature of the air in the space,
`generates a temperature signal having a cyclic parame(cid:173)
`ter which corresponds to the temperature of the air in
`the space as it rises and falls. A temperature changing
`means, including a refrigerant compressing means and a
`heat exchanging means, changes the temperature of the
`air. A variable speed motor drives the changing means
`in response to a motor control signal. Control means
`responds to the temperature signal and includes means
`for monitoring the cyclic parameter of the temperature
`signal. The control means generates the motor control
`signal as a function of the monitored cyclic parameter
`whereby said motor control signal is provided to the
`motor to control the torque or speed of the motor.
`Another embodiment of the invention comprises a
`device for driving a component of a heating and/or air
`conditioning system in response to a signal provided by
`a thermostat. A variable speed motor having a rotatable
`assembly in driving relation to the component, drives
`the component in response to a motor control signal. A
`programmable nonvolatile memory shores parameters
`representative of the system. Selected means selects at
`least one stored parameter. A microprocessor, respon(cid:173)
`sive to the selected parameter, generates motor control
`signals provided to the motor to control its speed,
`torque and/or air flow.
`In another embodiment of the invention, the control(cid:173)
`ler may be responsive to the temperature signal to sense
`the difference between a set point temperature and a
`temperature represented by the received temperature
`signal. The controller generates the motor control sig(cid:173)
`nal as a function of the difference whereby the motor
`
`8
`
`

`

`5,410,230
`
`3
`control signal is provided to the motor to control the
`torque or speed of the motor, or the air flow of the
`system.
`Other objects and features will be in part apparent
`and in part pointed out hereinafter.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a block diagram of a typical central heating
`and air conditioning (CHAC) variable speed control
`system according to the prior art including a system 10
`controller.
`FIG. 2 is a block diagram of a central heating and air
`conditioning (CHAC) variable speed control system
`embodying a preferred form of the present invention
`that does not require a system controller interposed 15
`between a thermostat and the remainder of the system.
`FIG. 3 is a block diagram of an electronically com(cid:173)
`mutated motor (ECM) drive system particularly
`adapted for carrying out the invention, the system in(cid:173)
`cluding a control system responsive to a two state tern- 20
`perature (T -STAT) signal.
`FIG. 4 is flow chart of one preferred embodiment of
`software which may be used to control the operation of
`a system embodying the invention in one form thereof.
`FIG. 5 is a graph illustrating refrigerant compressor 25
`RPMs, ambient temperature, set point temperature of a
`thermostat, temperature of the air space being moni(cid:173)
`tored by the thermostat, and time average of the com(cid:173)
`pressor RPMs of a system embodying the invention.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`Referring to FIG. 1, a typical heat pump variable
`speed control system now known in the art is illustrated
`in block diagram form. An electronic thermostat 102 35
`including a keyboard, such as a keypad, and a display,
`such as an LCD or LED display, is positioned within
`the air space. Thermostat 102 monitors the temperature
`of the air space so that the air space can be heated or
`cooled to maintain the air temperature within a range. 40
`Generally, thermostat 102 includes a function select
`which permits heating, cooling, or fan only operation of
`the system. Thermostat 102 also includes a temperature
`setting device or program permitting the user to select
`a preset temperature indicating the desired temperature 45
`of the air space. Thermostat 102 also includes some type
`of device for measuring the temperature of the air sur(cid:173)
`rounding thermostat 102. In response to this measured
`temperature, thermostat 102 provides a proportional
`temperature signal to a system controller 104 indicating 50
`the temperature of the air space. Thermostat 102 may
`also provide feedback information on its display to the
`user, such as confirming the programming or selection
`of the condition of the thermostat.
`System controller 104 monitors the difference be- 55
`tween the actual temperature of the air and the preset
`temperature which is desired, both of which are indi(cid:173)
`cated by electronic thermostat 102. This temperature
`difference is converted into a signal defming the speed
`and airflow rate of the system. This signal is provided 60
`via bus 106 to the indoor and outdoor units as com(cid:173)
`mands for controlling the speed and airflow rates. Gen(cid:173)
`erally, system controller 104 also includes a micro(cid:173)
`processor or other means for detecting system defaults
`and an algorithm which determine the actual tempera- 65
`ture control. If the system has an auxiliary heater 130,
`system controller 104 includes an auxiliary heater con(cid:173)
`trol which provides information to control the auxiliary
`
`4
`heater via control bus 106. System controller 104 com(cid:173)
`municates to the outdoor unit 108 via bus 106 providing
`information such as the functional selection as specified
`by thermostat 102, speed commands as determined by
`5 the temperature differential, defrost controls for de(cid:173)
`frosting cycling and fault conditions. System controller
`104 also communicates to the indoor unit 110 or 112 via
`bus 106 to specify an airflow command. Also, system
`controller 104 communicates with the thermostat 102 to
`provide feedback information to the user.
`Outdoor unit 108 includes a compressor 114 such as
`an electronically commutated motor (ECM) for driving
`a compressor. The compressor drive 114 may include a
`microprocessor or other circuit for controlling the com(cid:173)
`pressor speed and means for communicating with the
`system controller 104. The outdoor unit 108 also in-
`cludes a fan 118 including a speed control. Finally,
`outdoor unit 108 includes a control relays unit 120
`which controls the reversing valve 122 of the refrigera(cid:173)
`tion system, a defrost heater 124 activated to defrost the
`refrigeration system, and a sump heater 126 used for
`heating the sump compressor.
`Tile electrical indoor unit 110 includes a blower
`ECM 128 and heater relays 130 for operating an auxil(cid:173)
`iary heater(s). Alternatively, a gas furnace indoor unit
`112 includes an igniter 132 for igniting gas, a gas valve
`134 for selectively providing gas, a blower ECM 136
`and an optional draft inducer ECM 138, all operating in
`response to the system controller 104 which provides
`30 signals via bus 106.
`Referring now to FIG. 2, one preferred embodiment
`of a system according to the invention is shown in block
`diagram form. As compared to FIG. 1, the system of the
`invention illustrated in FIG. 2 eliminates the need for
`system controller 104. In particular, a conventional
`thermostat 202 is directly connected to a bus 204 which
`supplies information to both an outdoor unit 206 (e.g.,
`compressor and condenser units when working as an
`interior air cooling system; and compressor and evapo(cid:173)
`rator units when working as a heat pump system) or
`alternative indoor units 208 and 210. The conventional
`thermostat 202, such as a mechanical switch generating
`a two state (on/off) signal, includes a function select
`feature which permits the user to select heating, cooling
`or fan only operation. (In a room air conditioner or
`refrigeration environment, a heating option is not nor-
`mally provided, although a defrost or fan only setting
`may be provided, as will be understood). In addition,
`thermostat 202 has a temperature setting feature which
`permits the user to indicate a preselected temperature
`which is the desired temperature of the air surrounding
`the thermostat. Thermostat 202 also includes a device
`for measuring the temperature of the air surrounding
`the thermostat and generating a temperature signal such
`as an on/off signal provided via bus 204 to the indoor
`air moving and the compressor and condenser or evapo-
`rator outdoor units (in FIG. 3). The temperature signal
`has a cyclic parameter corresponding to the tempera(cid:173)
`ture of the air surrounding the thermostat. For example,
`the temperature signal for heating may be a two stake
`(on/oft) signal indicating that the air temperature is
`below/above the preselected temperature. Similarly,
`the temperature signal for cooling may be an on/off
`signal indicating that the air temperature is above/be(cid:173)
`low the preselected temperature. Preferably, the ther(cid:173)
`mostat 202 includes a feedback to the user indicating the
`approximate preset or desired temperature (e.g., a me(cid:173)
`chanical dial or digital readout).
`
`9
`
`

`

`5
`The on/off signals generated by thermostat 202 are
`provided via bus 204 to the compressor and condenser
`(or evaporator) unit 206. The unit 206 includes a com(cid:173)
`pressor with microprocessor control 211 such as an
`ECM which drives a compressor 212. The integral 5
`control of the compressor 211 monitors the thermostat
`duty cycle or other cyclic parameter of the on/off sig(cid:173)
`nal provided by thermostat 202. This monitored param(cid:173)
`eter is converted into a speed command which is used to
`control compressor 211 and may also be provided via 10
`line 213 to a condenser or evaporator fan ECM 214 to
`control the speed of a fan 215.
`Illustrated outdoor unit 206 also includes a control
`relay unit 216 responsive to the temperature signal for
`controlling a reversing valve 218 and a sump heater 220. 15
`It is to be expressly understood, however, that features
`such as these are not necessary for the practice of our
`invention.
`The on/off temperature signals generated by thermo(cid:173)
`stat 202 are also provided via bus 204 to an indoor con- 20
`denser/evaporator heat exchanging unit such as the
`indoor heat exchanger unit 208. This unit includes a
`blower ECM motor 222, a blower 223 and a heater
`relay 224. Both blower ECM 222 and heater relay 224
`have integral controls for converting the thermostat 25
`temperature signal cycling into an airflow signal com(cid:173)
`mand and generating an airflow control signal. Alterna(cid:173)
`tively, the indoor unit may be a gas furnace unit 210
`having an igniter 226 and a gas valve 228 responsive to
`the on/off thermostat signal. Additionally, the gas unit 30
`210 may include, as illustrated, a heat exchanger blower
`ECM motor 230 having an integral control responsive
`to the temperature signal cycling for driving a blower
`231. Gas unit 210 may also include an optional draft
`inducer ECM motor 232 (also responsive to such cy- 35
`cling) for driving a draft inducer 233.
`FIG. 3 is a block diagram of an ECM drive system
`300 that may be used for driving a compressor motor,
`fan motor, blower motor, or draft inducer fan motor as
`employed in the system illustrated in FIG. 2. Referring 40
`to FIG. 3, system 300 includes a microprocessor 302 for
`receiving the on/off temperature signal. A read only
`memory (ROM) 304, having software such as illustrated
`in FIG. 4, may be used to control the operation of the
`microprocessor 302. Microprocessor 302 provides a 45
`speed or torque control signal via line 308 to an elec(cid:173)
`tronically commutated motor 310 to control the speed
`or torque of the motor. Motor 310 has a rotatable assem(cid:173)
`bly mechanically connected via shaft 312 to the particu-
`lar compressor, blower, fan or draft inducer fan motor 50
`which it is driving. System 300 includes a power supply
`314 which provides low voltage power to operate the
`microprocessor 302 and also provides relatively higher
`voltage power to power the electronically commutated
`motor 310. Motor 310 may include means for sensing 55
`the position of its rotatable assembly such as a circuit
`314 for back electromotive force (BEMF) sensing
`which provides a speed signal to which microprocessor
`302 is responsive. Alternatively, other means such as,
`for example, hall devices may be used to indicate rotor 60
`position. Microprocessor 302 may include an analog-to(cid:173)
`digital converter for converting the temperature (T(cid:173)
`STAT) signal provided by conventional thermostat 202
`and/or the speed signal into a digital signal which is
`timed to determine the duty cycle of each state.
`FIG. 2 illustrates a system embodying a preferred
`form of the invention for conditioning air in a space by
`heating or cooling the air to change its temperature.
`
`65
`
`5,410,230
`
`6
`Conventional thermostat 202 constitutes means for gen(cid:173)
`erating a temperature signal having a cyclic parameter
`corresponding to the temperature of the air space as it
`rises and falls. This temperature signal is provided via
`bus 204. The indoor units 208 and 210 constitute means
`for changing the temperature and/or moisture content
`of the air. As shown in FIG. 3, ECM 310 constitutes a
`variable speed motor responsive to a motor control
`signal provided by microprocessor 302 via line 308 for
`driving the various portions of the system in response to
`the motor control signal. The microprocessor 302 con(cid:173)
`stitutes control means responsive to the temperature
`signal on bus 204 provided by thermostat 202. The
`microprocessor receives the temperature signal and
`monitors the cyclic parameter of the temperature signal
`to generate the motor control signal provided via line
`308 as a function of the monitored cyclic parameter.
`The control signal provided via line 308 is provided to
`ECM 310 as a motor control signal to control the torque
`or speed of the motor. In one preferred embodiment,
`the cyclic parameter comprises the on/off cycling rate
`of the two state temperature signal.
`As shown in FIG. 3, the microprocessor 302 may
`include a programmable, non-volatile (PNV) memory
`3041 storing parameters representative of the system
`such as time constants which are a function of the ther(cid:173)
`mal mass of the structure being heated and/or cooled.
`Alternatively, memory 3041 may store parameters rep(cid:173)
`resentative of the system characteristics which are used
`by micrporocessor 302 to determine operation of motor
`310. PNV memory 3041 may be an electrically erasea(cid:173)
`ble programmable read only memory (EEPROM). The
`microprocessor 302 may have a keypad or dip switches
`(not shown) responsive to operator input for selecting at
`least one of the stored parameters. The microprocessor
`308 generates control signals via line 308. Preferably,
`during operation in the cooling and/or heating mode,
`the microprocessor increases speed/airflow rate when
`the duty cycle of the temperature signal is above a pre(cid:173)
`set maximum. The microprocessor 302 decreases speed(cid:173)
`/airflow rate when the duty cycle of the temperature
`signal is below a preset minimum. In other words, if the
`thermostat calls for cooling for extended periods of
`time, the speed of the compressor and heat exchanger
`motors may be increased in order to increase the cool(cid:173)
`ing capacity of the system, so that more rapid cooldown
`may be achieved. On the other hand, if the thermostat
`rapidly cycles between "on" and "ofr', the compressor
`and heat exchanger motors may be slowed in order to
`achieve better humidity control and/or more efficient
`operation.
`In addition, it is contemplated that the cyclic parame(cid:173)
`ter may comprise the difference between a set point
`temperature of the thermostat and a temperature repre(cid:173)
`sented by the received temperature signal.
`In general, the thermostat may have contacts which
`close and open to provide the on/off or two state tem(cid:173)
`perature signal and also may have an anticipator which
`anticipates the opening of the thermostat contacts. In
`order to further enhance the efficiency, control and
`operation of the system according to the invention,
`microprocessor 302 may provide an output signal
`which adjusts the power level provided to the anticipa(cid:173)
`tor of the thermostat 202 as a function of the period of
`time during which the contacts of the thermostat 202
`are closed. In general, the power level of the anticipator
`may be adjusted as a function of the duty cycle of the
`temperature signal. The power level provided to the
`
`10
`
`

`

`7
`anticipator would decrease in response to an increase in
`the duty cycle of the temperature signal. This decrease
`may occur according to a linear algorithm. For exam(cid:173)
`ple, the algorithm may be as follows:
`
`QUI= UBASI- USLPI * RTEFF
`
`wherein QUI defines the anticipator value for the cur(cid:173)
`rent cycle selected as a function of the duty cycle;
`UBASI defines the baseline steady state anticipator
`temperature rise; USPLI defines the slope of the linear
`relation between the anticipator value and the duty
`cycle; and RTEFF is the duty cycle modified to ac(cid:173)
`count for a change in the motor rpm from start of last
`cycle to start of current cycle.
`Alternatively, the algorthim may be:
`
`QUI= UBASI- USLPI *RTIME
`
`wherein QUI defines the anticipator value for the cur(cid:173)
`rent cycle selected as a function of the duty cycle; 20
`UBASI defines the baseline steady state anticipator
`temperature rise; USPLI defines the slope of the linear
`relation between the anticipator value and the duty
`cycle; and R TIME is the duty cycle.
`If the system embodying the invention includes a heat 25
`pump or air conditioning compressor driven by the
`ECM 3IO, it is contemplated that the device being
`driven would have a predefined operating speed range.
`In this case, in one particular preferred embodiment of
`the invention, microprocessor 302 would initially oper- 30
`ate the compressor at the mid-point of its operating
`range. The operating speed would increase over time at
`a fixed rate during the period that the thermostat indi(cid:173)
`cated that the temperature of the air required additional
`conditioning. Furthermore, the microprocessor would 35
`decrease the operating speed of the compressor over
`time at a rate which is greater than the fixed rate of
`increase.
`Additionally, the EEPROM 304I may have one or
`more of the following parameters stored therein: speed 40
`or air flow rate for various operating modes such as a
`heating mode and a cooling mode; speed or air flow
`rates for different system capacities such as tons of cool(cid:173)
`ing and kilowatts of heating; parameters defming tum-
`on and tum-off time delays; parameters defining motor 45
`speed or torque changes over time; parameters defining
`the relationship between motor torque and air flow;
`parameters defming the relationship between motor
`speed and air flow; and parameters defining direction of
`rotations; and wherein the control signals generated by 50
`the microprocessor 302 are a function of at least one of
`the stored parameters. Alternatively, the EEPROM
`304I may include a parameter stored therein which is
`representative of a difference between the actual power
`input into the system and the expected nominal power 55
`so that the control signals generated by the micro(cid:173)
`processor 302 are a function of the difference.
`Referring to FIG. 3, variable speed motor 3IO has a
`rotatable assembly, or rotor, in driving relation to a
`component such as a compressor, blower, fan or draft 60
`inducer. System 300 is responsive to the control signals
`and has programmable nonvolatile (PNV) memory
`304I which stores parameters representative of system
`300. The motor control signal provided by micro(cid:173)
`processor 302 is responsive to at least one of the stored 65
`parameters plus the parameters selected in response to
`the parameter select signal and to the system control
`signal. System 300 provides the motor control signal to
`
`5,410,230
`
`15
`
`8
`ECM 3IO to control its speed or torque. ROM 304
`stores instructions which control the operation of mi(cid:173)
`croprocessor 302. The microprocessor 302 constitutes
`means responsive to the control signals provided by
`5 thermostat 202. The microprocessor 302 receives the
`temperature signal and monitors it to generate the
`motor control signal provided via line 308 as a function
`of the temperature signal and the stored parameters.
`Various time constants may be stored in PNV mem-
`10 ory 304I which correspond to various parameters of
`various environments. Microprocessor 302 may be pro(cid:173)
`grammed at the factory or during field installation to
`select time constants corresponding to the environ(cid:173)
`ments within which the indoor unit including system
`300 is being installed. The stored parameters may corre-
`spond to a constant CFM calibration, i.e., representa(cid:173)
`tive of a calibrated operation of the ECM 3IO driving a
`predetermined, known load so that microprocessor 302
`would be accurately responsive to the stored parame(cid:173)
`ters. Means for selecting parameters for calibration
`according to the invention is disclosed in co-pending
`application Ser. No. 07/889,708 filed May 27, 1992,
`which is incorporated herein by reference.
`As part of the process. of manufacture, system 300 is
`operated with a known calibration load with a predeter(cid:173)
`mined current versus speed characteristic. This load, for
`example, could be all ECM driving a blower wheel
`with a known restriction to the flow of air. It could also
`be an artificial load which electronically simulates the
`loading characteristics and waveforms present at the
`terminals of motor 3IO. The system 300 is calibrated by
`running it on this calibration load and commanding it to
`deliver, in sequence, one or more current levels to the
`load. For example, it may first be commanded to pro(cid:173)
`vide the full or maximum current level and then a rela-
`tively low current level. In each case, the actual current
`delivered by the system 300 is measured either directly
`or indirectly by measuring the speed achieved on the
`calibration load. Due to circuit tolerances within the
`particular system 300, the actual current values may be
`somewhat different from the correct or nominal values.
`This actual information generates a current offset factor
`and a multiplier factor compensating for the inaccura(cid:173)
`cies within the system 300. The compensation factors
`are stored permanently in the PNV memory 304I. In
`this manner, the system 300 is calibrated to compensate
`for the tolerance variations of its internal components.
`Alternatively, the parameters may be representative
`of a calibrated operation of ECM 3IO driving no load so
`that the microprocessor 302 is accurately responsive to
`such stored parameters. In the case of ECM 3IO, an
`alternate simplified method of calibration may be used.
`The system 300 is run at no load and the no load speed
`is measured. No load speed is a very good indicator of
`rotor magnetization level which is the predominant
`cause of torque variations. Storing this information
`along with the previously obtained control calibration
`information in an EEPROM used as PNV memory 304I
`allows subsequent compensation for most of such toler-
`ance variations. No load motor tests are much less time
`consuming than load tests and do not require a dyna(cid:173)
`mometer. As such, they are routinely performed any(cid:173)
`where. The built-in microprocessor 302 in the control
`can by itself measure the no load speed and store the
`data in the PNV memory 304I, requiring minimal exter(cid:173)
`nal equipment.
`
`11
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`

`5,410,230
`
`30
`
`9
`Alternatively, the parameters stored in PNV memory
`3041 may be representative of an operation of a particu-
`lar motor 310 in combination with a particular system
`300 to provide a representative operation of particular
`motor 310. For example, the stored parameters may 5
`represent the difference between the actual torque gen(cid:173)
`erated by a particular motor 310 and the nominal values
`thereby representing the combined inaccuracies of the
`particular motor 310 in combination with the micro(cid:173)
`processor 302. In a number of applications, the system 10
`300 and the motor 310 are physically attached together
`and distributed as a single unit. In such cases, the system
`300 would be programmed with not only its own inac(cid:173)
`curacies but also those of the motor 310 to which it is
`attached.
`Generally, the system 300 without motor 310 is first
`calibrated by one of the methods described above. The
`calibrated system is then connected to the motor 310.
`The system and motor combination are then calibrated,
`for example, by running them on a loading/measuring 20
`device such as a dynamometer. Certain torque level(s)
`are commanded of the system 300 and motor 310 and
`the resulting actual torques are measured. The differ(cid:173)
`ence between the actual torques and the correct or
`nominal values represents the combined inaccuracy of 25
`the system and the motor. This information is stored in
`the PNV memory 3041 to enable the microprocessor
`302 to produce near-nominal torque in the actual opera(cid:173)
`tion by compensating for the tolerance inaccuracies of
`both motor 310 and system 300.
`Thi