United States Patent
`
`[19]
`
`[11] Patent Number:
`
`4,648,551
`
`Thompson et a1.
`[45] Date of Patent: Mar. 10, 1987
`
`
`[54] ADAPTIVE BLOWER MOTOR
`CONTROLLER
`.
`_
`Inventors: Kevm D. Thompson3GaryW- Ballard.
`both of Indianapolis; Robert M.
`Mamot, Plainfield, all of Ind.
`
`[75]
`
`[73]
`
`Assignee: Carrier Corporation, Syracuse, NY.
`
`[21]
`
`App]. No.: 877,613
`
`[22]
`
`Filed:
`
`Jun. 23, 1986
`
`[51]
`[52]
`
`[58]
`
`Int. Cl.4 ................................................ F24F 7/00
`US. Cl. ............................... 236/49; 236/DIG. 9;
`165/40
`Field of Search ..................... 236/49, 11, DIG. 9;
`62/177, 186, 89, 158; 165/16, 40; 364/148, 557,
`551, 565
`
`
`SET MOTOR CONTROL
`& WAIT 2055C
`47' 50% DUTY CVCLé‘
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`3,912,162 10/1975 Bauer et a1. ........................... 236/11
`.....
`4,090,663
`5/1978 Bonne et a1.
`. 165/40 x
`
`1/1983 Breznican ................. 62/158
`4,370,605
`
`4,406,397
`9/1933 Kamata et a1.
`..
`236/DIG. 9
`4,549,601 10/1985 Wellmann et a].
`..
`......... 236/49 x
`
`
`Primary Examiner—Harry B. Tanner
`Attorney, Agent, or Firm—David J. Zobkiw
`
`[57]
`
`ABSTRACT
`
`An adaptive motor control for a furnace with or with-
`out an evaporator coil determines and delivers the de-
`sired 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.
`
`2 Claims, 6 Drawing Figures
`
`CALCULATE
`
`RPMDES
`
`INCR OR DECR
`M070? CONTROL IF
`
`EPA/(4‘7 95 RPMDES
` IS
`N0
`HIGH HEAT
`
`DESI’RED . l5
`236
`
`
` 254
`246
`252
`
` HAS
`SHUT GAS arr
`N0
`6 WET DELAY
`7'M45R 77MED
`
`TIMER
`OUT:
`
` Ill/CR 0/? DECR
`MOTOR CONWL IF
`
`RPM/K7- 9"RPMDES
`
`
`774531405727'
`Ansglso
`
`HEATING
`on coon/vs
`
`HEAT/”G
`
`COOLING
`
`SHUT OFF
`BLOWER
`
`250
`
`
`
`
`
`HONEYWELL - EXHIBIT 1003
`
`HONEYWELL - EXHIBIT 1003
`
`

`

`US. Patent Mar. 10,1987 .
`
`Sheet 1 of 5
`
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`
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`
`

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`

`1 .
`
`4,648,551
`
`2
`
`ADAPTIVE BLOWER MOTOR CONTROLLER
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`BACKGROUND OF THE INVENTION
`
`Tapped winding circulating air blower motors are
`used for air delivery in furnaces and the air delivery is
`factory matched for each speed tap for furnaces in-
`stalled with or without an evaporator coil. Most instal-
`lations, however, require modification of the factory
`settings to provide proper air delivery and this is done
`by changing the speed taps upon installation. Even if
`the motor speed is correct at installation, changes can
`occur within the system which require different motor
`settings to maintain the correct motor speed for the new
`conditions. These changed conditions can result from
`such causes as increased flow resistance due to dirty
`filters, closed ducts, reduced line voltage, and the in-
`crease in motor temperature. These changes cannot be
`controlled but they result in changes in the air delivery.
`SUMMARY OF THE INVENTION
`
`An electrically commutated motor (ECM) works off
`of a pulse input measured in percent of duty cycle and
`generates an RPM output signal characterized, for ex-
`ample, by thirty six pulses per rotation. To control an
`ECM so that it maintains appropriate air delivery for a
`specified air temperature rise or a given cooling load, a
`reference point has to be established. To do this, the
`CFM delivered must be calculated using the output
`from the ECM when set at a known duty cycle input.
`Knowing this reference point, the RPM necessary to
`obtain 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 accounted for on each thermostat cycle.
`It is an object of this invention to provide proper air
`delivery even when system conditions change.
`It is another object of this invention to provide two
`stage heating (high/low) while maintaining the flow of
`combustion air at the optimum level. These objects, and
`others as will become apparent hereinafter, are accom-
`plished by the present invention.
`Basically, an ECM is energized and operated at an
`arbitrary pulse width say 50% for approximately 15 to
`20 seconds to allow the motor RPM to stabilize. This
`RPM is then used to establish the necessary RPM for
`proper air delivery.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`For a fuller understanding of the present invention,
`reference should now be made to the following detailed
`description thereof taken in conjunction with the ac-
`companying drawings wherein:
`FIG. 1 is a partially cutaway side view of a condens-
`ing furnace having an evaporator coil and incorporating
`the principles of the present invention:
`FIG. 2 is a block diagram of a portion of the furnace
`control system;
`FIG. 3 is a standard fan curve for static pressure in
`inches of water column (I.W.C.) vs. CFM at various
`torques in ounce feet and RPMs; and
`FIG. 4 shows how FIGS. 4A and 4B are related.
`FIGS. 4A and 4B show a flow diagram of the motor
`control.
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`In FIG. 1, the numeral 10 generally designates a
`gas-fired condensing furnace employing the adaptive
`motor control of the present invention. Condensing
`furnace 10 includes a steel cabinet 12 housing therein
`burner assembly 14, combination gas control 16, heat
`exchanger assembly 18, inducer housing 20 supporting,
`inducer motor 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 inshot
`burner 28 for at least one primary heat exchanger 30.
`Burner 28 receives a flow of combustible gas from gas
`regulator 16 and injects the fuel gas into primary heat
`exchanger 30. A part of the injection process includes
`drawing air into heat exchanger assembly 18 so that the
`fuel gas and air mixture may be combusted therein. A
`flow of combustion‘air is delivered through combustion
`air inlet 32 to be mixed with the gas delivered to burner
`assembly 14.
`Primary heat exchanger 30 includes an outlet 34
`opening into chamber 36. Connected to chamber 36 and
`in fluid communication therewith are at least four con-
`densing heat exchangers 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 is connected to chamber 44 and
`has mounted thereon an inducer motor 22 together with
`inducer wheel 24 for drawing the combusted fuel air
`mixture from burner assembly 14 through heat ex-
`changer assembly 18. Air blower 26 is driven by elec-
`tronically commutated motor (ECM) 25 and delivers
`air to be heated in a counterflow arrangement upwardly
`through air passage 52 and over heat exchanger assem-
`bly 18. The cool air passing over condensing heat ex-
`changer 38 lowers 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 mixture to condense, thereby recovering a por-
`tion of the sensible and latent heat energy. The conden-
`sate formed within heat exchanger 38 flows through
`chamber 44 into drain tube 46 to condensate trap assem-
`bly 48. As air blower 26 continues to urge a flow of air,
`upwardly through heat exchanger assembly 18, heat
`energy is transferred from the combusted fuel air mix-
`ture flowing through heat exchangers 30 and 38 to heat
`the air circulated by blower 26. Finally, the combusted
`fuel air mixture that flows through heat exchangers 30
`and 38 exits through outlet 42 and is then delivered by
`inducer motor 22 through exhaust gas outlet 50 and
`thence to a vent pipe (not illustrated).
`Cabinet 12 also houses microprocessor control assem-
`bly 54, LED display 56, pressure tap 58 located at pri-
`mary heat exchanger inlet 60, pressure tap 62 located at
`condensing heat exchanger outlet 42 and limit switch 64
`disposed in air passage 52. In a non-condensing furnace,
`pressure tap 62 would be disposed at primary heat ex-
`changer 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 of air condi-
`tioning system 180 which is schematically shown in
`FIG. 2. The cooling coil 82 has an inlet 84, where sub-
`cooled refrigerant enters, and an outlet 86, where super-
`heated refrigerant leaves, as is conventional. In response
`to an input from heating/cooling thermostat 182, air
`
`

`

`4,648,551
`
`3
`blower 26 urges air flow upwardly through cooling coil
`82 where heat exchange takes place. As a result of this
`heat exchange, cool air is delivered to the conditioned
`space and superheated refrigerant is returned to the
`outdoor condensing section (not illustrated) via outlet
`86. In the outdoor condensing section the refrigerant is
`subcooled and returned to inlet 84. This cycle continues
`until the thermostat 182 is satisfied.
`Referring now to FIG. 2, microprocessor control 148
`is located in microprocessor control assembly 54 in
`condensing furnace 10 and is capable of being prepro-
`grammed to generate a plurality of control signals in
`response to received input signals. The simplified block
`diagram illustrates the interconnection between micro-
`processor control 148 and pressure taps 58 and 62
`through differential pressure transducer 156 which gen-
`erates an analog signal indicative of the differential
`pressure. Microprocessor control 148 is also electrically
`connected to limit switch 64,
`to gas regulator 16
`through electrical lines 152, to air blower motor control
`160 of ECM 25 of air blower 26 through electrical lines
`162, to inducer motor control 164 of inducer motor 22
`through electrical lines 166, to air conditioning system
`180 through electrical lines 181 and to thermostat 182
`through electrical lines 183. Air blower motor control
`160 and inducer motor control 164 respectively control
`the rate of fluid flow created.by air blower 26 and indu-
`cer wheel 24. Ignition of the pilot control of gas regula-
`tor 16 and a signal is generated to microprocessor con-
`trol 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 ex-
`changer assembly 18 through pressure taps 58 and 62
`which transmit pressure readings to differential pressure
`transducer 156. Differential pressure transducer 156
`sends a pressure differential signal indicative of the
`pressure drop across heat exchanger assembly 18
`through electrical lines 158 to microprocessor control
`148. After microprocessor control 148 determines that a
`sufficient pressure drop exists across heat exchanger
`assembly 18, that the gas pressure in gas regulator 16 is
`at or above a predetermined pressure, and the pilot
`flame has been proved, microprocessor control 148 is
`programmed to generate a voltage signal through elec-
`trical 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 is combusted by
`inshot burner 28.
`
`then drawn
`The combusted fuel air mixture is
`through heat exchanger assembly 18 and out exhaust
`gas outlet 50 by the rotation of inducer wheel 24 by
`motor 22. After a preselected period of time, for exam-
`ple, one minute, to ensure that heat exchanger assembly
`18 has reached a predetermined temperature, micro-
`processor control 148 is preprogrammed to generate a
`signal through 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 exchanger 30. Any con-
`densate 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 supplying of fuel. This natu-
`
`4
`rally causes the pilot flame and burner flame to be extin-
`guished.
`After gas control 16 is de-energized, microprocessor
`control 148 generates a signal over electrical lines 166 to
`inducer motor control 164 to terminate operation of
`inducer motor 22. After inducer motor 22 has been
`de-energized, microprocessor control 148 is further
`preprogrammed to generate a signal over lines 162 to air
`blower motor control 160 to de—energize ECM 25,
`thereby terminating operation of air blower 26, after a
`preselected period of time, for example, 60—240 secs
`onds. This continual running of air blower 26 for this
`predetermined amount of time permits further heat
`transfer between the air to be heated and the heat being
`generated through heat exchanger assembly 18, which
`also 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, microprocessor control 148 is prepro-
`grammed to ensure an optimum manifold gas pressure
`as a function of the amount of combustion air flowing
`through combustion air inlet 32 under the influence of
`inducer wheel 24. The pressure drop across heat ex-
`changer assembly 18 is measured by pressure taps 58
`and 62 which transmit their individual pressure readings
`to differential pressure transducer 156. Transducer 156
`then generates a pressure differential signal to micro-
`processor control 148 over electrical lines 158 indica-
`tive of the pressure drop across heat exchanger assem-
`bly 18. An empirically determined equation for opti-
`mum manifold gas pressure versus heat exchanger pres-
`sure drop is programmed into microprocessor control
`148 whereby it determines the optimum manifold gas
`pressure for a particular pressure drop across heat ex-
`changer assembly 18, as indicated by the pressure differ-
`ential signal received from differential pressure trans-
`ducer 156. As the pressure drop varies, microprocessor
`control 148 generates a signal to gas regulator 16 over
`electrical lines 152 to regulate the fuel supply. During
`continued operation of furnace 10, microprocessor con-
`trol 148 continues to make adjustments in the gas flow
`rate and pressure as a function of certain variable pa-
`rameters, such as line pressure, dirty filters, closed
`ducts, supply voltage, temperature changes, vent pipe
`length, furnace altitude, and the like. Thus, gas control
`16 and microprocessor control 148 provide essentially
`an infinite number of gas flow rates between a zero flow
`rate and a maximum flow rate in a selected range of, for
`example, two inches to fourteen inches W.C. (water
`column).
`Determination of insufficient or too much combus-
`tion air flowing through combustion air inlet 32 is deter-
`mined by the pressure drop across heat exchanger as-
`sembly 18. This pressure drop is measured by pressure
`taps 58 and 62 and a signal is generated in response
`thereto by differential pressure transducer 156 to micro-
`processor control 148. Generally, for each pressure
`differential value, there is one optimum manifold gas
`pressure and one optimum combustion air flow rate.
`Thus, assuming the manifold gas pressure is substan—
`tially constant, variations in certain parameters can
`require adjustment to the combustion air flow rate as
`provided by inducer wheel 24.
`Upon determining insufficient combustion air flow
`through burner assembly 14, as indicated by a low pres-
`sure drop across heat exchanger assembly 18, micro-
`processor control 148 generates a speed increase signal
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`60
`
`65
`
`

`

`5
`to inducer motor control 164 to increase the combustion
`air flow rate through burner assembly 18 and increase
`the pressure drop across heat exchanger assembly 18. In
`a similar manner, microprocessor control 148 can deter-
`mine insufficient flow of air to be heated through fur-
`nace 10 by activation of temperature limit switch 64
`which will open when the temperature in air passage’52
`exceeds a predetermined temperature limit.
`The cooling function is achieved by air conditioning
`system 180, which is controlled by microprocessor con-
`trol 148 responsive to the thermostat 182. ECM 25 and
`air blower motor control 160 are common to both the
`heating and cooling function for driving air blower 26.
`Except for ECM 25 and air blower motor control 160
`and their operation, the air conditioning system 180
`operates in a conventional fashion.
`From the foregoing description, it is clear that the
`ECM 25 must be accurately controlled by microproces-
`sor control 148 to optimize operation of furnace 10 and
`air conditioning system 180. To achieve the necessary
`control, it is necessary to have a calibrated response. An
`ECM 25, such as is available from General Electric as
`part number 5SME39HGH69IT, varies speed with a
`change in percent duty cycle and air blower motor
`control 160 generates an RPM output signal of 36 pulses
`per revolution. To control ECM 25 so that it maintains
`an appropriate air delivery for a specified air tempera-
`ture rise or for, a given cooling load, a reference RPM
`and CFM must be established.
`The fan curves illustrated in FIG. 3 are used in con-
`junction with the procedure set forth in FIG. 4A and
`4B. As indicated by box 200, the ECM blower motor 25
`is turned on in response to a blower on signal in re-
`sponse to a sensed temperature deviation by thermostat
`182 and, as indicated by box 202, the air blower motor
`control 160 is initially set at a predetermined, arbitrary,
`50% duty cycle by microprocessor control 148 for 20
`seconds. Because ECM motor 25 generates an RPM
`output signal characterized 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 RPM, the CFM can be calculated, as
`indicated by box 206, from equation (1).
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`CFM=2161.24—[(1.212)(RPM)]
`
`(1)
`
`45
`
`With a known RPM and CFM we can now locate a
`point on FIG. 3 which locates the constant system line
`for a 50% duty cycle. When the constant system line is
`located, the desired RPM, RPMDES, which delivers the
`desired CFM, CFMDES, can be determined directly
`from FIG. 3 or can be calculated as indicated in box
`218, from equation (2), the fan law equation:
`
`50
`
`RPMDEs=RPM (CFMDEs/CFM)
`
`(2)
`
`55
`
`As indicated by box 208, responsive to the temperature
`in the area to be conditioned and the thermostatic set-
`ting, the microprocessor control sets the system in ei-
`ther a heating or a cooling mode. Assuming first a heat-
`ing mode, box 210, a decision must then be made by
`microprocessor control 148, as indicated by box 212, as
`to whether the system should be in the low heat or high
`heat mode. The major difference between high and low
`heat is the different CFMDES air delivery that passes
`around the heat exchangers 30 and 38. With the lesser
`amount of air being circulated in the low heat mode, a
`CFMDES of 667 CFM is to be achieved, as indicated by
`block 214, _while in the high heat mode with the greater
`
`65
`
`4,648,551
`
`6
`amount of air being circulated a CFMDES of 1234 CFM
`is to be achieved, as indicated by box 216. It should be
`noted that more heat is removed from the heat exchang-
`ers in the high heat mode due to the increased air flow
`which is necessary because of the increased gas input
`rate.
`
`If the system is in cooling mode, as indicated by box
`220, the mode must be selected by microprocessor con-
`trol 148 from 2 tons, 2; tons or 3 tons of cooling, as
`indicated by box 222. The three cooling modes have
`respective desired CFM outputs, (CFMDEs) of 800,
`1000 and 1200 as indicated by boxes 224, 226, and 228.
`With the desired heating CFM from box 214 or 216 or
`from one of the coolingmodes indicated by boxes 224,
`226, or 228 as an input,
`the desired motor speed
`(RPMDES) is calculated, as indicated by box 218, from
`equation 2 where RPM is the initial RPM from box 204
`and CFM is the initial CFM from box 206. With
`RPMDES calculated,
`the RPM is
`read and called
`RPMACT as indicated by box 230. The motor control
`160 is then incremented or decremented one step if
`RPMAczyéRPMDEsas indicated by box 232. After this,
`it is necessary to determine whether the system is in the
`high heat mode, as indicated by box 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 so,
`the logic returns to box 216. If it is determined in box
`234 that the system is in high heat, or if it is determined
`in box 236 that high heat is not desired, it is then neces-
`sary to determine whether or not the thermostat is satis-
`fied, as indicated by box 238. If the thermostat is not
`satisfied, the logic returns to box 230 where RPMAcris
`read again. This logic continues to repeat itself until the
`thermostat is satisfied. When the thermostat is satisfied
`the microprocessor control checks to see if thesystem is
`in either a heating or cooling mode as indicated by box
`240. Assuming first a heating mode, as indicated by box
`242, the heating gas supply is shut off and the off delay
`timer is started, as indicated by box 244, RPMACT is
`read, as indicated by box 246, then motor controller 160
`is incremented or decremented if RPMAc7¢RPMDEs
`as shown in box 248, this is done so that the residual heat
`will be delivered from the heat exchanger to the area to
`be conditioned. If it is determined in box 252 that the
`timer has not timed out the logic returns to box 246
`where RPMACT is read again. This logic continues to
`repeat itself until the timer times out. The blower motor
`is then shut off as indicated in box 252. If the system is
`in cooling mode as indicated by box 250 the blower
`motor is 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 motor control was set at a 50% duty cycle at
`box 202 and that the motor controller speed input signal
`was incremented or decremented at box 232. In achiev-
`ing this change, there is a change in RPMACT. This
`process is then repeated until RPMACT= RPMDES.
`If any system variations occur, each thermostat cycle
`allows 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. Ulti-
`mately this system change either increases or decreases
`RPMDES so the proper air delivery is provided.
`This process is illustrated using the FIG. 3 diagram
`by taking the steps of boxes 202, 204 and 206 which
`gives the 50% duty cycle point for the determined
`RPM and CFM and this locates a constant system line.
`
`.
`
`

`

`4,648,551
`
`8
`
`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;
`if 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.
`*
`II
`t
`t
`t
`
`7
`By following the constant system line to where, it inter-
`sects the desired CFM line, one can determine the de-
`sired RPM.
`
`This process also requires manual calibration of the
`ECM motor 25 and ECM control 160 to achieve a
`constant CFM air delivery. Calibration is necessary
`because of the inconsistencies with electronic compo-
`nents and motor magnet strength.
`Although a preferred embodiment of the present
`invention has been illustrated and described, changes
`will occur to those skilled in the art. It is therefore
`intended that the scope of the present invention is to be
`limited only by the scope of the appended claims.
`What is claimed is:
`
`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 predeter-
`mined set point;
`if the sensed temperature deviates from the predeter-
`mined set point by more than a predetermined amount,
`operating the ECM at a predetermined duty cycle for a
`sufficient time for stabilization;
`determining the RPM:
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`60
`
`65
`
`