CA1274295A - Adaptive blower motor controller - Google Patents
Adaptive blower motor controllerInfo
- Publication number
- CA1274295A CA1274295A CA000537722A CA537722A CA1274295A CA 1274295 A CA1274295 A CA 1274295A CA 000537722 A CA000537722 A CA 000537722A CA 537722 A CA537722 A CA 537722A CA 1274295 A CA1274295 A CA 1274295A
- Authority
- CA
- Canada
- Prior art keywords
- rpm
- ecm
- air
- determining
- cfm
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/50—Control or safety arrangements characterised by user interfaces or communication
- F24F11/61—Control or safety arrangements characterised by user interfaces or communication using timers
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/62—Control or safety arrangements characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
- F24F11/63—Electronic processing
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/70—Control systems characterised by their outputs; Constructional details thereof
- F24F11/80—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air
- F24F11/81—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the air supply to heat-exchangers or bypass channels
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D23/00—Control of temperature
- G05D23/19—Control of temperature characterised by the use of electric means
- G05D23/1906—Control of temperature characterised by the use of electric means using an analogue comparing device
- G05D23/1913—Control of temperature characterised by the use of electric means using an analogue comparing device delivering a series of pulses
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/30—Control or safety arrangements for purposes related to the operation of the system, e.g. for safety or monitoring
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F2110/00—Control inputs relating to air properties
- F24F2110/10—Temperature
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F2110/00—Control inputs relating to air properties
- F24F2110/40—Pressure, e.g. wind pressure
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F2140/00—Control inputs relating to system states
- F24F2140/50—Load
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S236/00—Automatic temperature and humidity regulation
- Y10S236/09—Fan control
Abstract
ADAPTIVE BLOWER MOTOR CONTROLLER
ABSTRACT OF THE DISCLOSURE
An adaptive motor control for a furnace with or without an evaporator coil determines and delivers the desired CFM for each thermostat cycle. Specifically, a circulating air blower driven by an ECM is initially set at a known duty cycle for each thermostat cycle and the delivered CFM is calculated. The RPM necessary to deliver the desired CFM is then determined and the ECM is set accordingly.
ABSTRACT OF THE DISCLOSURE
An adaptive motor control for a furnace with or without an evaporator coil determines and delivers the desired CFM for each thermostat cycle. Specifically, a circulating air blower driven by an ECM is initially set at a known duty cycle for each thermostat cycle and the delivered CFM is calculated. The RPM necessary to deliver the desired CFM is then determined and the ECM is set accordingly.
Description
~17 ~ ~5 ADAP~IVE BLOWER MOTOR CONTROLLER
Background of the Invent _ Tapped winding circulating air blower motors are used for alr delivery in furnaces and the air delivery i~ factory matched for each speed tap Eor furnaces installed with or without an evaporator coil. Most installations, however, requlre modification of the factory settings to provide proper alr delivery and this is done by changing the speed taps upon installation. Even if the motor speed is correct at instal-lation, changes can occur within the system which require differcnt motor settings to maintain the corrcct motor speed for the new conditions. These changed conditions can result from such causes aR increased flow resistancc due to dirty filters, closed duc~s, reduced line voltage, and the increase in motor temperature. These changes cannot be controlled but they result in changes in the air delivery.
Summary of ~he Invention An electrlcally commutated notor (ECM) work~ off of a pulse input measured in percent of duty cycle and generates an RPM
output signal characterized, for example, by thirty six pulses per rotation. To co~ltrol an ECM so that it maintains appropriate air delivery for a speciEied air temperature rise or a given coollng load, a reference point ha~ to be estab-lished. To do this, the CFM delivered mu8t be calculated u~ing the output from the ECM when set at a kn~wn duty cycle input. Knowing this reference point, the RPM necessary to obtaln a desired CFM air delivery can be calculated. The microprocessor then adjusts the duty cycle input until the desired RPM is obtained. All system variations are then accoun~ed for on each thermostat cycle.
It i8 an object of this invention to provide proper air delivery even when system condi~ions change.
~.~7~95 It is another objçct of this invention to provide two stage heating ~high/low) while maintsining the flow cf combustion aix at the optimum level. These objects, and others as will become apparent hereina~ter, flre accomplished by the present invention.
Basically, an ECM is energized and operated at an arbitrary pulæe wid~h s~y 50% for approximately 15 to 20 seconds to allow the motor RPM to stabilize. This RPM i8 then used to establish the necessary RPM for proper ~ir delivery.
Brief Description of the Drawin~6 For a fuller understanding of the pre~ent invention, refer-ence should now be made to the following detailed descriptlon thereof taken in conjunction with the accompanying drawings wh~rein:
Figure 1 i8 a partially cutaway side view of a condensing ~ furnace having ~n evaporator coil and incorporating the principle~ of the presen~ invention;
Figure 2 i~ a block diagr~m of a por~ion of the furnace control system;
Figures 4A and 4B show a flow diagram of the motor control.
Figure 3 i~ a standard fan curve for ~tatic pressure in inches of water column (I.W.C.) vs. CF~I at ~ariou6 torques ~n ounce feet and RPMs; and Figure 4 shows how Figures 4A and 4B are related.
Description of the Preferred Embodiment In Figure 1. the numeral 10 generally designates a gas-fired oondensing furnace employing the adaptive motor control of the present invention. Condensing furnace 10 includes a steel cabinet 12 housing therein burner assembly 14, c~mbins-tion gas control 16, hPflt exchanger ~ssembly 18, inducer ~ 5 housing 20 suppor,ting inducer mo~or 22 and inducer wheel 24, and circulating air blower 26. Combination gas control 16 includes pilot circuitry for controlling and providing the pilot flame~
Burner assembly 14 includes at least one in~hot burner 28 for at leas~ one primary heat exchanger 30. Burner 28 receives a flow of combustlble gas from gas regulator 16 and injects the fuel gas into primary heat exchanger 30. A part of the injection process includes ~rawing air in~o heat exchanger assembly 18 90 that the fuel gas and air mixture may ble combusted ~herein. A flow of combustion air i9 delivered through combustion air inlet 32 to be mixed with the gas delivered to burner assembly 14.
Primary hea~ exchanger 30 includes an outlet 34 opening into chamber 36. Connected to chamber 36 and in fluid communica-tion therewith are at least four condensing heat exchang~rs 38 having an inlet 40 and an outlet 42. Outlet 42 opens into chamber 44 for venting exhaust flue gases and condensate.
Inducer housing 20 i~ connected to chamber 44 and has mounted thereon an inducer motor 22 together with inducer wheel 24 for drawing the combusted fuel air mix~ure from burner a~sembly 14 through heat exchanger assembly 18. Air blower 26 is driven by electronically commutated motor (ECM) 25 and delivers air to be heated in a counter10w arrangement upwardly ~hrough air passage 52 and over heat exchanger assembly 18. The cool air passing over conden~ing heat exchanger 38 low~rs the heat exchanger wall temperature below the dew point of the combusted fuel air mixture causing a portion of the water vapor in the combusted fuel air m~xture to condense, thereby recoverin~ a portion of the sensible and latent heat energy. The condensate formed within heat exchanger 38 flows through chamber 44 into drain tube 46 to condensate trap assembly 48. As air blower 26 continues to ~4~5 urge a flow of air upwardly through heat e~changer assembly 18, heat energy is transferre~ from the combusted fuel air ~ixture flowing through heat exchangers 3() and 38 ~o heat ~he air circulated by blower 26. Final1y, the combusted fuel air mixture that flows ~hrough heat exchangers 30 and 38 exits through outlet 42 and is then delivered by inducer motor 22 through exhaust gas outle~ 50 and thence t:o a vent pipe (not illu8 trated~. -Cabinet 12 also houses microprocessor control assembly 54,LED display 56, pres~ure tap 58 located at primary heat exchQIlger inlet 60, pressure tap 62 located at condensing heat exchanger outlet 42 and limi~ switch 64 disposed in air passage 52. In a non-condensing furnace9 pressure tap 62 would be disposed at primary heat exchanger outlet 34, since there would be no condensing heat exchanger 38.
A cooling coil 82 is located in housing 80 on top of furnace cabinet 10 and is the evaporator ~f air condi~ioning system 180 which is schematically shown in Figure 2. The cooling coil 82 has an inlet 84, where subcooled refrigerant enters, and an outlet 86, where superheated refrigerant leaves, a~ 18 conventional. In response to an inpu~ from hea~ing/cooling thermostat 182, air blower 26 urges air flow upwardly ~hrough cooling coil 82 where heat exchange takes place. As a result of this heat exchange, cool air i8 delivered to the condi-tioned space and sup~r~eated refrigerant i8 returned to the outdoor condensing section (not illustrated) via outlet 86.
In the outdoor condensing sectlon the refriger~nt is subcooled and returned to inlet 84. This cycle continues until the thermostat 182 is sati~fied.
Referring now to Figure 2, microprocessor control 148 is located in microprocessor control assembly 54 in condensing furnace 10 and is capable of being preprogrammed to gensrate a plurality of control signals in response to received input ~.~74,":9~
slgnals. The simplified block diagram illustrates the interconnection between mlcroprocessor control 148 and pressure taps 58 and 62 through differential pressure trans-ducer 156 which generates an analog signal indicative of the d:Lffererltial pressure. Microprocessor control 148 is also electrïcally connected to limit switch 64, ~o gas regulator 16 through electrical lines 152, to air blower motor control 160 of ECM 25 of air blower 26 ~hrough electrical line8 162, to inducer motor control 164 o~ inducer motor 22 through electrical lines 166, to air conditioning system 180 through electrical lines 181 and to thermostat 182 through electrlcal llnes 183. Alr blower motor control 160 and inducer motor control 164 respectively control the rate of fluid flow created by air blower 26 and inducer wheel 24. Ign~tion of the pilot control of gas regulator 16 and a signal is gener-ated to microprocessor control 148 through electrical lines 152 to indicate that the flame is proved.
During this period of time~ microprocessor control 148 is monitoring the pressure drop across heat exchanger assembly 18 through pressure ~aps 58 and 62 which tran4mit pressure xeading~ to differential pressure transducer 156. Differen-tial pressure transducer 156 sends a pressure differential si~nal indicative of the pressure drop across heat exchanger assembly 18 through electrical lines 158 to microprocessor control 148. After microprocessor control 148 determines tha~ a sufficient pressure drop exists across heat exchanger assembly 18, that the gas pressure in gas regulator 16 is at or above a ~redetermined pressure, and the pilot~flame has been proved, mlcroprocessor control 148 is programmed ~o generate a voltage signal through electrical lines 152 to a solenoid ~not illustrated) in regulator 16 for controlling gas flow.
Gas flow is provided by gas regulator 16 to burner assembly 14 and the fuel air mixture i~ combusted by inshot burner 28, The combusted fuel air mixture is then drawn through heat exchan~er assembly 18 and out exhaust gas outlet 50 by the rotation of inducer wheel 24 by motor 22. After a prese-lected period of time, for example, one minute, to ensure tha~ heat exchanger assembly 18 has reached a predc~ermined ~emperature, microprocessor control l~lB i.s preprogrammed to g~nerate a signal throllgh electrical lines 162 to air blower motor control 160, which starts ECM 25 of air blower 26 to provide a flow of air to be heated over condensing heat exchanger 38 and primary heat Pxchanger 30. Any condensate that forms in condensing heat exchanger 38 is delivered through drain tube 46 to condensate trap assembly 48. After the heating load has been satisfied, the contacts of the thermostat 182 open, and in response thereto microprocessor control 148 de-energizes gas regulator 16 ceasing the supply-ing o fuel. This naturally causes the pilo~ flame and burner flame to be ex~inguished.
After gas control 16 is de-ellergized, microprocessvr control 148 generates a signal over electrical lines 166 to inducer motor con~rol 164 to terminate opera~ion of inducer motor 22.
After inducer motor 22 has been de-energized, microprocessor control 148 i6 further preprogrammed to generate a signal over lines 162 to air blower motor control 160 to de-energize ECM 25, thereby termina~ing operation o~ air blower 26, after a preselec~ed period of time, for example, 60-240 seconds.
This continual running of air blower 26 for this prede~er-mined amount of ~ime permits further heat transfer between the air to be heated and the heat being generated through heat exchanger assembly 18, which al80 naturally serves to cool heat exchanger assembly 18.
Because the pressure drop across heat exchanger assembly 18 can vary due to changing conditions or parameters, micropro-cessor control 148 is preprogrammed to ensure an optimummanifold gas pressure as ~ func~ion o~ the amount of ~ ~ 7~
combustion air fl~wing through combustion air lnlet 32 under the influence of inducer wheel 24. The presGure drop across hea~ exchanger assembly 18 is measured by pressure taps 58 and 62 whlch transmit their indlvidual pressure readings to differential pressure transducer 156. Transducer 156 then generates a pressure differential slgnal ~o microprocessor control 148 over electrical lines 158 indicative of the pressure drop across heat exchanger assembly 18. An empiri-cally determined equation for op~imum man~fold gas pressure versus heat exchanger pressure drop is programmed into microprocessor control 148 whereby it determines the optimum manifold gas pressure for a particular pressure drop across heat exchanger assembly 18, as indicated by the pressure differential signal received from di~ferential pressure transducer 156. As the pressure drop varies, microprocessor control 148 generates a signal to gas regulator 16 over electrical lines 152 to regulate ~he fuel supply. During continued operation of furnace 10, microprocessor control 148 continues to make adjustments in the gas flow rate and pressure as a function of certain variable parameters, such as line pressure, dirty filters, closed ducts, supply volt-age, temperature changes, vent pipe length, furnace altitude, and the like. Thus~ gas con~rol 16 and microprocessor control ll~8 provide essentially an infinite number of gas flow rates between a zero flow ra~e and a maximum flow rate in a selected range of, for example, two inches to four~een inches W.C. (water column).
De~ermination of insufficient or too much combustion air flowing through combuætion air inlet 32 i9 determined by the pressure drop across heat e~changer assembly 18. This pressure drop i9 measured by pressure tap9 58 and 62 and a ~igrlal i8 generated in re~ponse thereto by differential pressure transducer 156 to microprocessor control 148.
Generally, for each pressure differential value, there is one optimum manifold gas pr~ssure and one optimum combustion air ~ 95 flow rate. Thus, assuming ~he ~lanifold gas pre6sure i9 substant~ally constant, variations itl certair- parameters can require adjusttnent to the combus~ion air 10w rate as provld-ed by inducer wll~el 2l~, Upon determit~ing insufficient combustion air flow through burner assembly 14, as lndicated by a low pressure drop across hea~ exchanger assembly l~, microproces~or control 148 genPrates a speed increase ~gnal to inclucer motor control lQ 164 to increase the combustion air flow rate through burner assembly 18 and increase the pressure drop across heat exchanger a~sembly 18. In a similar manner, microprocessor control 148 can determine insufficient flow of air to be heated through furnace 10 by activa~ion of temperature limit switch 64 which will open when tlle temperature in air passage 52 exceeds a predetermined temperature limit.
The cooling function ls achieved by ~ir conditioning system 180,which i~ controlled by microprocessor control 148 respon-sive to the thermostat 182. ECM 25 and air blower motor control 160 are common -to both the heating and coollng function for drivin~ alr blower 26~ Except for ECM 25 and air blower motor control 160 and their operation, the air conditioning sys tem 1~0 operates in a conventional fashion.
~rom the foregoing description, it i8 clear tlla~ the ECM 25 mus~ be accurately controlled by microprocessor control 148 to optimlze operation of furnace lO and air conditioning system 180. To achieve the necessary control, it i~ nece~-sary to have a calibrated response. An ECM 25, such as i8 available from General Electric as part number 5SME39HG~l691T, varies speed wi~h a change in percent duty cycle and air blower motor control 160 generates an RPM output signal of 36 pulses per revolution. To control ~CM 25 80 that it main-tains an appropriate air del~very for a speciiied air temper-~ 9~3 .
ature rise or for a given cooling lo~d, a reference RPM and CFM must be established.
The f~n curves illustrated in Fl~ure 3 are used in conjunc-5 tlon with the procedure set forth in Figures ~IA and 4B. As indicated by box 200, the E,CM blower motor 25 i8 turned on in response to a blower on 6ignal in response to a sen6ed temper~ture dev~ation by thermostat 182 and, as indicated by box 202, the air blower motor control 160 is ini~iAlly ~et at a predeter-mined, arbitrary, 50Z duty cycle by microprocessor control148 for 20 second6. Because ECM motor 25 generates an RPM
output signal charact~rized by thirty six pulses per rota-tion, the RPM at the 50% duty cycle can be read out directly from motor control 160 as indicated by box 204, Knowing the RP~I, the CFM can be calculated, as indicated by box 206, from : equation (1).
CFM = 2161.24 - [(1.212)(RPM)~
W~th a known RP~ and CFM we can now loc~te a point on Figure 3 ~hich locates the constant syste~ line for ~ 50% duty cyc~e. ~he~ the constant sy~tem lîne is located, the desired RPM, RPMDES, which deliver~ the desired CFM, C ~ Es, can be determined dlrectly from Figure 3 or can be calculated as indic~ted in box 218, from equ~tion ~2), the an law equatlon:
RPMDES - RPM ~CFMDES/CFM) ~ ?~
As indica~ed by box 208, responsive ~o the temper~ture in the area to be conditioned and the ther~ostatic setting, the m~croprocessor control sets the system in either a heatlng or a cooling mode. Assuming first a heating mode, box 210, ~
decislon must then be made by microprocessor control 148, as indic~ted by ~ox 212, a6 to whether the Bystem should be in the low heat or high heat mode4 The major difference between high and low heat is the different CFMDES air delivery that pas~es ~round the he~t exchangers 30 and 38. W~th the lesser a~ount of air being circulated in tlle low hea~ mode, a CPMDES
o G67 CFM is to be achieved, as indicated by block 214~
while in ~he high heat ~ode with the greater ~mount of air being oirculated a CEMD~S oi 1234 CFM is to be achie~ed, as indicated by box 216. It should be noted th~t more heat i8 removed from the heat exchanger~ ln the high heat mode due to the increased air flow which i~ necessary because of the increased gas input .ate.
If the system is in cooling mode, as indicated by box 220, the mode must be selected by mlcroprocessor control 148 from
Background of the Invent _ Tapped winding circulating air blower motors are used for alr delivery in furnaces and the air delivery i~ factory matched for each speed tap Eor furnaces installed with or without an evaporator coil. Most installations, however, requlre modification of the factory settings to provide proper alr delivery and this is done by changing the speed taps upon installation. Even if the motor speed is correct at instal-lation, changes can occur within the system which require differcnt motor settings to maintain the corrcct motor speed for the new conditions. These changed conditions can result from such causes aR increased flow resistancc due to dirty filters, closed duc~s, reduced line voltage, and the increase in motor temperature. These changes cannot be controlled but they result in changes in the air delivery.
Summary of ~he Invention An electrlcally commutated notor (ECM) work~ off of a pulse input measured in percent of duty cycle and generates an RPM
output signal characterized, for example, by thirty six pulses per rotation. To co~ltrol an ECM so that it maintains appropriate air delivery for a speciEied air temperature rise or a given coollng load, a reference point ha~ to be estab-lished. To do this, the CFM delivered mu8t be calculated u~ing the output from the ECM when set at a kn~wn duty cycle input. Knowing this reference point, the RPM necessary to obtaln a desired CFM air delivery can be calculated. The microprocessor then adjusts the duty cycle input until the desired RPM is obtained. All system variations are then accoun~ed for on each thermostat cycle.
It i8 an object of this invention to provide proper air delivery even when system condi~ions change.
~.~7~95 It is another objçct of this invention to provide two stage heating ~high/low) while maintsining the flow cf combustion aix at the optimum level. These objects, and others as will become apparent hereina~ter, flre accomplished by the present invention.
Basically, an ECM is energized and operated at an arbitrary pulæe wid~h s~y 50% for approximately 15 to 20 seconds to allow the motor RPM to stabilize. This RPM i8 then used to establish the necessary RPM for proper ~ir delivery.
Brief Description of the Drawin~6 For a fuller understanding of the pre~ent invention, refer-ence should now be made to the following detailed descriptlon thereof taken in conjunction with the accompanying drawings wh~rein:
Figure 1 i8 a partially cutaway side view of a condensing ~ furnace having ~n evaporator coil and incorporating the principle~ of the presen~ invention;
Figure 2 i~ a block diagr~m of a por~ion of the furnace control system;
Figures 4A and 4B show a flow diagram of the motor control.
Figure 3 i~ a standard fan curve for ~tatic pressure in inches of water column (I.W.C.) vs. CF~I at ~ariou6 torques ~n ounce feet and RPMs; and Figure 4 shows how Figures 4A and 4B are related.
Description of the Preferred Embodiment In Figure 1. the numeral 10 generally designates a gas-fired oondensing furnace employing the adaptive motor control of the present invention. Condensing furnace 10 includes a steel cabinet 12 housing therein burner assembly 14, c~mbins-tion gas control 16, hPflt exchanger ~ssembly 18, inducer ~ 5 housing 20 suppor,ting inducer mo~or 22 and inducer wheel 24, and circulating air blower 26. Combination gas control 16 includes pilot circuitry for controlling and providing the pilot flame~
Burner assembly 14 includes at least one in~hot burner 28 for at leas~ one primary heat exchanger 30. Burner 28 receives a flow of combustlble gas from gas regulator 16 and injects the fuel gas into primary heat exchanger 30. A part of the injection process includes ~rawing air in~o heat exchanger assembly 18 90 that the fuel gas and air mixture may ble combusted ~herein. A flow of combustion air i9 delivered through combustion air inlet 32 to be mixed with the gas delivered to burner assembly 14.
Primary hea~ exchanger 30 includes an outlet 34 opening into chamber 36. Connected to chamber 36 and in fluid communica-tion therewith are at least four condensing heat exchang~rs 38 having an inlet 40 and an outlet 42. Outlet 42 opens into chamber 44 for venting exhaust flue gases and condensate.
Inducer housing 20 i~ connected to chamber 44 and has mounted thereon an inducer motor 22 together with inducer wheel 24 for drawing the combusted fuel air mix~ure from burner a~sembly 14 through heat exchanger assembly 18. Air blower 26 is driven by electronically commutated motor (ECM) 25 and delivers air to be heated in a counter10w arrangement upwardly ~hrough air passage 52 and over heat exchanger assembly 18. The cool air passing over conden~ing heat exchanger 38 low~rs the heat exchanger wall temperature below the dew point of the combusted fuel air mixture causing a portion of the water vapor in the combusted fuel air m~xture to condense, thereby recoverin~ a portion of the sensible and latent heat energy. The condensate formed within heat exchanger 38 flows through chamber 44 into drain tube 46 to condensate trap assembly 48. As air blower 26 continues to ~4~5 urge a flow of air upwardly through heat e~changer assembly 18, heat energy is transferre~ from the combusted fuel air ~ixture flowing through heat exchangers 3() and 38 ~o heat ~he air circulated by blower 26. Final1y, the combusted fuel air mixture that flows ~hrough heat exchangers 30 and 38 exits through outlet 42 and is then delivered by inducer motor 22 through exhaust gas outle~ 50 and thence t:o a vent pipe (not illu8 trated~. -Cabinet 12 also houses microprocessor control assembly 54,LED display 56, pres~ure tap 58 located at primary heat exchQIlger inlet 60, pressure tap 62 located at condensing heat exchanger outlet 42 and limi~ switch 64 disposed in air passage 52. In a non-condensing furnace9 pressure tap 62 would be disposed at primary heat exchanger outlet 34, since there would be no condensing heat exchanger 38.
A cooling coil 82 is located in housing 80 on top of furnace cabinet 10 and is the evaporator ~f air condi~ioning system 180 which is schematically shown in Figure 2. The cooling coil 82 has an inlet 84, where subcooled refrigerant enters, and an outlet 86, where superheated refrigerant leaves, a~ 18 conventional. In response to an inpu~ from hea~ing/cooling thermostat 182, air blower 26 urges air flow upwardly ~hrough cooling coil 82 where heat exchange takes place. As a result of this heat exchange, cool air i8 delivered to the condi-tioned space and sup~r~eated refrigerant i8 returned to the outdoor condensing section (not illustrated) via outlet 86.
In the outdoor condensing sectlon the refriger~nt is subcooled and returned to inlet 84. This cycle continues until the thermostat 182 is sati~fied.
Referring now to Figure 2, microprocessor control 148 is located in microprocessor control assembly 54 in condensing furnace 10 and is capable of being preprogrammed to gensrate a plurality of control signals in response to received input ~.~74,":9~
slgnals. The simplified block diagram illustrates the interconnection between mlcroprocessor control 148 and pressure taps 58 and 62 through differential pressure trans-ducer 156 which generates an analog signal indicative of the d:Lffererltial pressure. Microprocessor control 148 is also electrïcally connected to limit switch 64, ~o gas regulator 16 through electrical lines 152, to air blower motor control 160 of ECM 25 of air blower 26 ~hrough electrical line8 162, to inducer motor control 164 o~ inducer motor 22 through electrical lines 166, to air conditioning system 180 through electrical lines 181 and to thermostat 182 through electrlcal llnes 183. Alr blower motor control 160 and inducer motor control 164 respectively control the rate of fluid flow created by air blower 26 and inducer wheel 24. Ign~tion of the pilot control of gas regulator 16 and a signal is gener-ated to microprocessor control 148 through electrical lines 152 to indicate that the flame is proved.
During this period of time~ microprocessor control 148 is monitoring the pressure drop across heat exchanger assembly 18 through pressure ~aps 58 and 62 which tran4mit pressure xeading~ to differential pressure transducer 156. Differen-tial pressure transducer 156 sends a pressure differential si~nal indicative of the pressure drop across heat exchanger assembly 18 through electrical lines 158 to microprocessor control 148. After microprocessor control 148 determines tha~ a sufficient pressure drop exists across heat exchanger assembly 18, that the gas pressure in gas regulator 16 is at or above a ~redetermined pressure, and the pilot~flame has been proved, mlcroprocessor control 148 is programmed ~o generate a voltage signal through electrical lines 152 to a solenoid ~not illustrated) in regulator 16 for controlling gas flow.
Gas flow is provided by gas regulator 16 to burner assembly 14 and the fuel air mixture i~ combusted by inshot burner 28, The combusted fuel air mixture is then drawn through heat exchan~er assembly 18 and out exhaust gas outlet 50 by the rotation of inducer wheel 24 by motor 22. After a prese-lected period of time, for example, one minute, to ensure tha~ heat exchanger assembly 18 has reached a predc~ermined ~emperature, microprocessor control l~lB i.s preprogrammed to g~nerate a signal throllgh electrical lines 162 to air blower motor control 160, which starts ECM 25 of air blower 26 to provide a flow of air to be heated over condensing heat exchanger 38 and primary heat Pxchanger 30. Any condensate that forms in condensing heat exchanger 38 is delivered through drain tube 46 to condensate trap assembly 48. After the heating load has been satisfied, the contacts of the thermostat 182 open, and in response thereto microprocessor control 148 de-energizes gas regulator 16 ceasing the supply-ing o fuel. This naturally causes the pilo~ flame and burner flame to be ex~inguished.
After gas control 16 is de-ellergized, microprocessvr control 148 generates a signal over electrical lines 166 to inducer motor con~rol 164 to terminate opera~ion of inducer motor 22.
After inducer motor 22 has been de-energized, microprocessor control 148 i6 further preprogrammed to generate a signal over lines 162 to air blower motor control 160 to de-energize ECM 25, thereby termina~ing operation o~ air blower 26, after a preselec~ed period of time, for example, 60-240 seconds.
This continual running of air blower 26 for this prede~er-mined amount of ~ime permits further heat transfer between the air to be heated and the heat being generated through heat exchanger assembly 18, which al80 naturally serves to cool heat exchanger assembly 18.
Because the pressure drop across heat exchanger assembly 18 can vary due to changing conditions or parameters, micropro-cessor control 148 is preprogrammed to ensure an optimummanifold gas pressure as ~ func~ion o~ the amount of ~ ~ 7~
combustion air fl~wing through combustion air lnlet 32 under the influence of inducer wheel 24. The presGure drop across hea~ exchanger assembly 18 is measured by pressure taps 58 and 62 whlch transmit their indlvidual pressure readings to differential pressure transducer 156. Transducer 156 then generates a pressure differential slgnal ~o microprocessor control 148 over electrical lines 158 indicative of the pressure drop across heat exchanger assembly 18. An empiri-cally determined equation for op~imum man~fold gas pressure versus heat exchanger pressure drop is programmed into microprocessor control 148 whereby it determines the optimum manifold gas pressure for a particular pressure drop across heat exchanger assembly 18, as indicated by the pressure differential signal received from di~ferential pressure transducer 156. As the pressure drop varies, microprocessor control 148 generates a signal to gas regulator 16 over electrical lines 152 to regulate ~he fuel supply. During continued operation of furnace 10, microprocessor control 148 continues to make adjustments in the gas flow rate and pressure as a function of certain variable parameters, such as line pressure, dirty filters, closed ducts, supply volt-age, temperature changes, vent pipe length, furnace altitude, and the like. Thus~ gas con~rol 16 and microprocessor control ll~8 provide essentially an infinite number of gas flow rates between a zero flow ra~e and a maximum flow rate in a selected range of, for example, two inches to four~een inches W.C. (water column).
De~ermination of insufficient or too much combustion air flowing through combuætion air inlet 32 i9 determined by the pressure drop across heat e~changer assembly 18. This pressure drop i9 measured by pressure tap9 58 and 62 and a ~igrlal i8 generated in re~ponse thereto by differential pressure transducer 156 to microprocessor control 148.
Generally, for each pressure differential value, there is one optimum manifold gas pr~ssure and one optimum combustion air ~ 95 flow rate. Thus, assuming ~he ~lanifold gas pre6sure i9 substant~ally constant, variations itl certair- parameters can require adjusttnent to the combus~ion air 10w rate as provld-ed by inducer wll~el 2l~, Upon determit~ing insufficient combustion air flow through burner assembly 14, as lndicated by a low pressure drop across hea~ exchanger assembly l~, microproces~or control 148 genPrates a speed increase ~gnal to inclucer motor control lQ 164 to increase the combustion air flow rate through burner assembly 18 and increase the pressure drop across heat exchanger a~sembly 18. In a similar manner, microprocessor control 148 can determine insufficient flow of air to be heated through furnace 10 by activa~ion of temperature limit switch 64 which will open when tlle temperature in air passage 52 exceeds a predetermined temperature limit.
The cooling function ls achieved by ~ir conditioning system 180,which i~ controlled by microprocessor control 148 respon-sive to the thermostat 182. ECM 25 and air blower motor control 160 are common -to both the heating and coollng function for drivin~ alr blower 26~ Except for ECM 25 and air blower motor control 160 and their operation, the air conditioning sys tem 1~0 operates in a conventional fashion.
~rom the foregoing description, it i8 clear tlla~ the ECM 25 mus~ be accurately controlled by microprocessor control 148 to optimlze operation of furnace lO and air conditioning system 180. To achieve the necessary control, it i~ nece~-sary to have a calibrated response. An ECM 25, such as i8 available from General Electric as part number 5SME39HG~l691T, varies speed wi~h a change in percent duty cycle and air blower motor control 160 generates an RPM output signal of 36 pulses per revolution. To control ~CM 25 80 that it main-tains an appropriate air del~very for a speciiied air temper-~ 9~3 .
ature rise or for a given cooling lo~d, a reference RPM and CFM must be established.
The f~n curves illustrated in Fl~ure 3 are used in conjunc-5 tlon with the procedure set forth in Figures ~IA and 4B. As indicated by box 200, the E,CM blower motor 25 i8 turned on in response to a blower on 6ignal in response to a sen6ed temper~ture dev~ation by thermostat 182 and, as indicated by box 202, the air blower motor control 160 is ini~iAlly ~et at a predeter-mined, arbitrary, 50Z duty cycle by microprocessor control148 for 20 second6. Because ECM motor 25 generates an RPM
output signal charact~rized by thirty six pulses per rota-tion, the RPM at the 50% duty cycle can be read out directly from motor control 160 as indicated by box 204, Knowing the RP~I, the CFM can be calculated, as indicated by box 206, from : equation (1).
CFM = 2161.24 - [(1.212)(RPM)~
W~th a known RP~ and CFM we can now loc~te a point on Figure 3 ~hich locates the constant syste~ line for ~ 50% duty cyc~e. ~he~ the constant sy~tem lîne is located, the desired RPM, RPMDES, which deliver~ the desired CFM, C ~ Es, can be determined dlrectly from Figure 3 or can be calculated as indic~ted in box 218, from equ~tion ~2), the an law equatlon:
RPMDES - RPM ~CFMDES/CFM) ~ ?~
As indica~ed by box 208, responsive ~o the temper~ture in the area to be conditioned and the ther~ostatic setting, the m~croprocessor control sets the system in either a heatlng or a cooling mode. Assuming first a heating mode, box 210, ~
decislon must then be made by microprocessor control 148, as indic~ted by ~ox 212, a6 to whether the Bystem should be in the low heat or high heat mode4 The major difference between high and low heat is the different CFMDES air delivery that pas~es ~round the he~t exchangers 30 and 38. W~th the lesser a~ount of air being circulated in tlle low hea~ mode, a CPMDES
o G67 CFM is to be achieved, as indicated by block 214~
while in ~he high heat ~ode with the greater ~mount of air being oirculated a CEMD~S oi 1234 CFM is to be achie~ed, as indicated by box 216. It should be noted th~t more heat i8 removed from the heat exchanger~ ln the high heat mode due to the increased air flow which i~ necessary because of the increased gas input .ate.
If the system is in cooling mode, as indicated by box 220, the mode must be selected by mlcroprocessor control 148 from
2 tons, 2~ tons or 3 tons of cooling, as indica~ed by box 222. The three cooling modes have respective desired CF~l outputs, (CFMD~S) of 800, 1000 and 1200 as indlcated by boxes 224, 226, and 228. With the desired heating CFM from box 21 or 216 or from one of the coollng modes indicated by boxes 224" 226, or 228 as an input, the desired motor 6peed (RP ~ ES) is caiculated, as indicated by box 21B, from equation 2, where RPM is tlle lnltisl RPM from box 204 and CFM
is the initial CF~5 from box 206. With RP~ ES calculated, the RPM is read and called RPMACT as indicated by box 230. The : motor control 160 is then incremented or decremented one ~tep if RPPIAcT ~ RP ~ ES as indicated by box 232. After this, it is necessary to determine whether the system i8 ln the high heat mode, as indicated by bo~ 234. If the system is not in the high heat mode, it is necessary to determine if high heat is desired, as indicated by box 236, and, if 80j the logic returns to box 216. If it is determined in box 234 that the 6ystem is in high heat, or if it is determinad in box 236 that high heat i8 not desired, i~ iB then necessary to determlne whether or not the thermoatat i8 satisfied, as indicated by box 238. If the thermostat i~ not satisfied, the logic returns to box 230 where RPMACT iY read again.
Thia logic continues to repeat itsel~ until the thermo~tat i9 ~\
~ ~4~ ~5 satisfled. When the thermostat i6 satisfied the microproces-sor control checks tu see iE the system i~ in either a heuting or cooling mode as indlcated by box 240. ~ssuming first a heating mode, as indicated by box 242, the hea~irlg ga~supply iB sllut off and tlle of~ delay timer is started, as indica~ed by box 244, RP~ACT i9 read, as indicated by box 246, ~hen motor controller 160 is incremerlted or decreme~lted lf RPM ~ RP ~ ES as shown in box 24~, this is done so that the residual heat will be delivered from the heat exchanger to the area to be conditioned. If it i8 determined in box 252 that the timer has not timed out the logic r~turns to box 246 where RP~tACT is read again, This logic con~inues to repeat itself until ~he timer times out. The blower motor i~
then shut of as indic~ted in box 252. If the syst~m i9 ln cooling mode as indlcated by box 250 the blower motor i8 then shut off as shown in box 254. No delay off time is necessary in the cooling mode.
It should be noted that in the foregoing description that the 2~ motor controllwas set at a 50% duty cycle at box 202 and that the motor controller speed input signal was incr~mented or decremented at box 232. In achieving thi~ change, there is a change in RPMA~T, This process is then repeated until ~PM,j~CT = RPMDE S
I arly system variations occur, each thermostat cycle ~llows the program to compensate for the change in load which is indicated by a change in RPM at box 204~ which results in a change in CFM at box 206. ~ltimately this ~ystem change either in~reases or decrease8 RP ~ES so the proper air delivery is provided.
This process is illustrated using the Figure 3 diagr~m by taking the s~eps of boxes 202, 204 and 206 which gives the 35 50Z duty cycle point for the dete~milled RPM and CFM and this locates a constant system line. By following the constant system line to whe,re it intersects the desired CF~I line, one can determine the desired RPM.
This process also requires manual calibration of the ECM
S motor 25 and ECM control 160 to achieve a con~tant CFM air delivery. Calibration i9 necessary b~caluse of the inconsis-tencies wi~h electronic components and ~otor magnet strength.
Although a preferred embodiment of the presen~ invention has been illu~trated and described, changes will occur to those skilled in the art. It i8 ~herefore intlended that the scope of the present inven~ion ls to be limited only by the scope Df the appended claim~.
is the initial CF~5 from box 206. With RP~ ES calculated, the RPM is read and called RPMACT as indicated by box 230. The : motor control 160 is then incremented or decremented one ~tep if RPPIAcT ~ RP ~ ES as indicated by box 232. After this, it is necessary to determine whether the system i8 ln the high heat mode, as indicated by bo~ 234. If the system is not in the high heat mode, it is necessary to determine if high heat is desired, as indicated by box 236, and, if 80j the logic returns to box 216. If it is determined in box 234 that the 6ystem is in high heat, or if it is determinad in box 236 that high heat i8 not desired, i~ iB then necessary to determlne whether or not the thermoatat i8 satisfied, as indicated by box 238. If the thermostat i~ not satisfied, the logic returns to box 230 where RPMACT iY read again.
Thia logic continues to repeat itsel~ until the thermo~tat i9 ~\
~ ~4~ ~5 satisfled. When the thermostat i6 satisfied the microproces-sor control checks tu see iE the system i~ in either a heuting or cooling mode as indlcated by box 240. ~ssuming first a heating mode, as indicated by box 242, the hea~irlg ga~supply iB sllut off and tlle of~ delay timer is started, as indica~ed by box 244, RP~ACT i9 read, as indicated by box 246, ~hen motor controller 160 is incremerlted or decreme~lted lf RPM ~ RP ~ ES as shown in box 24~, this is done so that the residual heat will be delivered from the heat exchanger to the area to be conditioned. If it i8 determined in box 252 that the timer has not timed out the logic r~turns to box 246 where RP~tACT is read again, This logic con~inues to repeat itself until ~he timer times out. The blower motor i~
then shut of as indic~ted in box 252. If the syst~m i9 ln cooling mode as indlcated by box 250 the blower motor i8 then shut off as shown in box 254. No delay off time is necessary in the cooling mode.
It should be noted that in the foregoing description that the 2~ motor controllwas set at a 50% duty cycle at box 202 and that the motor controller speed input signal was incr~mented or decremented at box 232. In achieving thi~ change, there is a change in RPMA~T, This process is then repeated until ~PM,j~CT = RPMDE S
I arly system variations occur, each thermostat cycle ~llows the program to compensate for the change in load which is indicated by a change in RPM at box 204~ which results in a change in CFM at box 206. ~ltimately this ~ystem change either in~reases or decrease8 RP ~ES so the proper air delivery is provided.
This process is illustrated using the Figure 3 diagr~m by taking the s~eps of boxes 202, 204 and 206 which gives the 35 50Z duty cycle point for the dete~milled RPM and CFM and this locates a constant system line. By following the constant system line to whe,re it intersects the desired CF~I line, one can determine the desired RPM.
This process also requires manual calibration of the ECM
S motor 25 and ECM control 160 to achieve a con~tant CFM air delivery. Calibration i9 necessary b~caluse of the inconsis-tencies wi~h electronic components and ~otor magnet strength.
Although a preferred embodiment of the presen~ invention has been illu~trated and described, changes will occur to those skilled in the art. It i8 ~herefore intlended that the scope of the present inven~ion ls to be limited only by the scope Df the appended claim~.
Claims (2)
1. An adaptive motor control for regulating an ECM driven circulating air blower for each thermostat cycle comprising the steps of:
sensing the temperature in an area to be conditioned;
comparing the sensed temperature to a predetermined set point;
if the sensed temperature deviates from the prede-termined set point by more than a predetermined amount, operating the ECM at a predetermined duty cycle for a suffi-cient time for stabilization;
determining the RPM;
determining the CFM;
determining whether heating or cooling is required;
if heating is required, determining whether high or low heat is required;
if cooling is required, determining the amount of cooling required;
selecting the desired CFM for the required heating or cooling;
determining the desired RPM for the selected desired CFM;
determining the actual RPM;
adjusting the speed of the ECM if the actual and desired RPM are not the same;
determining whether the thermostat is satisfied;
if the thermostat is not satisfied, returning to the step of determining the actual RPM;
is the thermostat is satisfied, determining whether the system is in the heating or cooling mode, if in the cooling mode, shutting off the blower;
and;
if in the heating mode, shutting off the gas and then shutting off the blower after a predetermined time.
sensing the temperature in an area to be conditioned;
comparing the sensed temperature to a predetermined set point;
if the sensed temperature deviates from the prede-termined set point by more than a predetermined amount, operating the ECM at a predetermined duty cycle for a suffi-cient time for stabilization;
determining the RPM;
determining the CFM;
determining whether heating or cooling is required;
if heating is required, determining whether high or low heat is required;
if cooling is required, determining the amount of cooling required;
selecting the desired CFM for the required heating or cooling;
determining the desired RPM for the selected desired CFM;
determining the actual RPM;
adjusting the speed of the ECM if the actual and desired RPM are not the same;
determining whether the thermostat is satisfied;
if the thermostat is not satisfied, returning to the step of determining the actual RPM;
is the thermostat is satisfied, determining whether the system is in the heating or cooling mode, if in the cooling mode, shutting off the blower;
and;
if in the heating mode, shutting off the gas and then shutting off the blower after a predetermined time.
2. The adaptive motor control of claim 1 further including the step of continuing to adjust the speed of the ECM if the actual and desired RPM are not the same until the blower is shut off.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US877,613 | 1986-06-23 | ||
| US06/877,613 US4648551A (en) | 1986-06-23 | 1986-06-23 | Adaptive blower motor controller |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1274295A true CA1274295A (en) | 1990-09-18 |
Family
ID=25370331
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000537722A Expired - Lifetime CA1274295A (en) | 1986-06-23 | 1987-05-22 | Adaptive blower motor controller |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US4648551A (en) |
| JP (1) | JPS633672A (en) |
| CA (1) | CA1274295A (en) |
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| US4978896A (en) * | 1989-07-26 | 1990-12-18 | General Electric Company | Method and apparatus for controlling a blower motor in an air handling system |
| US4982721A (en) * | 1990-02-09 | 1991-01-08 | Inter-City Products Corp. (Usa) | Restricted intake compensation method for a two stage furnace |
| US5019757A (en) * | 1990-03-19 | 1991-05-28 | General Electric Company | Method and apparatus for controlling a blower motor in an air handling system to provide constant pressure |
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| US5423192A (en) * | 1993-08-18 | 1995-06-13 | General Electric Company | Electronically commutated motor for driving a compressor |
| US5202951A (en) * | 1991-06-05 | 1993-04-13 | Gas Research Institute | Mass flow rate control system and method |
| US5237338A (en) * | 1991-08-05 | 1993-08-17 | Eastman Kodak Company | Is-enthalpic control of a thermal printing head |
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| EP0571122B1 (en) * | 1992-05-20 | 1998-08-12 | Texas Instruments Incorporated | Method and apparatus for enhancing relay life |
| US5473229A (en) * | 1992-05-27 | 1995-12-05 | General Electric Company | Interface between programmable electronically commutated motor and personal computer and method of operation |
| US5492273A (en) * | 1992-05-27 | 1996-02-20 | General Electric Company | Heating ventilating and/or air conditioning system having a variable speed indoor blower motor |
| US5592058A (en) * | 1992-05-27 | 1997-01-07 | General Electric Company | Control system and methods for a multiparameter electronically commutated motor |
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| US5680021A (en) * | 1993-02-22 | 1997-10-21 | General Electric Company | Systems and methods for controlling a draft inducer for a furnace |
| US5616995A (en) * | 1993-02-22 | 1997-04-01 | General Electric Company | Systems and methods for controlling a draft inducer for a furnace |
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| US6504338B1 (en) * | 2001-07-12 | 2003-01-07 | Varidigm Corporation | Constant CFM control algorithm for an air moving system utilizing a centrifugal blower driven by an induction motor |
| KR20020031367A (en) * | 2002-03-26 | 2002-05-01 | 윤대성 | The air condition system using enthalpy in a outsider temperature |
| US7177534B2 (en) | 2003-09-17 | 2007-02-13 | Air System Components, L.P. | System and method for controlling heating and ventilating systems |
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| US3912162A (en) * | 1973-12-07 | 1975-10-14 | Robertshaw Controls Co | Furnace blower speed control |
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| JPS6047497B2 (en) * | 1981-05-25 | 1985-10-22 | 東プレ株式会社 | Air volume control device for central air conditioning equipment |
| US4549601A (en) * | 1982-06-21 | 1985-10-29 | Carrier Corporation | Variable volume multizone system |
| JPS5983555A (en) * | 1982-11-04 | 1984-05-15 | Sumitomo Metal Ind Ltd | Controlling method for air flow rate of motor cooling fan |
-
1986
- 1986-06-23 US US06/877,613 patent/US4648551A/en not_active Expired - Lifetime
-
1987
- 1987-05-22 CA CA000537722A patent/CA1274295A/en not_active Expired - Lifetime
- 1987-05-29 JP JP62134801A patent/JPS633672A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS633672A (en) | 1988-01-08 |
| US4648551A (en) | 1987-03-10 |
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