US3877243A

US3877243A - Refrigeration systems including evaporator with 2 speed fan motor

Info

Publication number: US3877243A
Application number: US401265A
Authority: US
Inventors: Daniel E Kramer
Original assignee: Daniel E Kramer
Current assignee: Ardco Inc
Priority date: 1973-09-27
Filing date: 1973-09-27
Publication date: 1975-04-15
Anticipated expiration: 1992-04-15

Abstract

A refrigeration system having a compressor driven by a motor having a control for turning it on and off, and an evaporator which includes a motor driven fan where the fan motor can operate at high speed or at low speed, and where the fan motor is connected to operate at high speed when the compressor motor is on and to operate at low speed when the compressor motor is off.

Description

' United States Patent Kramer 1 Apr. 15, 1975 [54] REFRIGERATION SYSTEMS INCLUDING 3,034,314 5/1962 Cantcs 62/180 P FAN 3,070,972 1/1963 Atchison 62/180 EX$ WITH 2 S EED 3,398,889 8/1968 Bohannan 62/180 3,505,828 4/1970 Vander Molen 62/180 [76] Inventor: Daniel E. Kramer, 2009 Woodland 3,514,967 0 Vander 0 6 9 2/180 Dr, Yardley, p 190 7 3,517,523 6/1970 Brown 62/180 [22] Flled: Sept. 1973 Primary ExaminerWi11iam J. Wye

[21] App]. No.: 401,265

[57] ABSTRACT [52] US. Cl. 62/180; 62/181; 62/186; A refrigeration System having a compressor driven by 62/183 a motor having a control for turning it on and off, and [51] Int. Cl. F25d 17/00 an evaporator which includes a motor driven fan [58] Field of Search 62/180, 186, 181, 183 where the fan motor can Operate at high Speed or at low speed, and where the fan motor is connected to [56] References Clted operate at high speed when the compressor motor is UNITED STATES PATENTS on and to operate at low speed when the compressor 2,195,924 4/1940 Hoesel 62/89 motor is Off. 2,236,058 3/1941 Henneym, 62/180 2,970,455 2 1961 Slattery 62/180 1 Clalm, 5 Drawmg Figures 5A m z 21321 283 2:20 2cz1 I 1 2C3 14 e1 321ao| 12s 1 N1 1 REFRIGERATION SYSTEMS INCLUDING EVAPORATOR WITH 2 SPEED FAN MOTOR BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to refrigeration systems with evaporators which cool air forced over them by motor driven fans, and especially to power savings that result during periods that the compressor is not in operation when the speed and therefore the power input to the evaporator fan motor is sharply reduced by means set forth herein.

2. Description of the Prior Art Refrigeration systems employing evaporators having motors which drive fans for the purpose of drawing or blowing air over the evaporator for the purpose ofcooling that air well known. It is currently normal practice, when refrigeration evaporators are applied to cooler or freezer boxes, to leave fan motors on the evaporators running at full speed whether the compressor is in operation or not. On medium temperature systems, that is, those systems operating to cool rooms to between 45 and 32, the practice of leaving the evaporator fans running has some basis because the frost that is depos ited on the surfaces of the refrigerating coil during thqse periods that the compressor is operating is defrosted by the passage of air warmer than 32 during those periods when the compressor is not operating.

BRIEF SUMMARY OF THE INVENTION The invention is an improvement in the design of refrigeration systems employing air cooling evaporators which use motors to drive the air over the evaporator surfaces. It is known that motors utilize less energy when running at low speed than at high speed. With the recent shortage of electrical energy caused by wide spread. and increasing shortage of the fossil fuels used V to generate electricity. increasing thought has been given to improvements in refrigeration machinery that would provide the same cooling but at a lower power cost.

This invention relates to the reduction in overall power consumption for the systems required to refrigerate a cooler or freezer where the evaporators are equipped with motors for driving their fans which are capable of operating at full speed while consuming full power and at lower speed while consuming less power. This invention is directed toward a refrigeration system with an evaporator using motors capable of operating at higher and lower speeds. and the control arrangement whereby the motors driving the evaporator fans operate at higher speed during those periods that the compressor is on where full air flow is necessary in order to achieve full cooling effect, and lower speed when the compressor is off with consequent reduction in the power that the fan motors consume those periods when the compressor is off. In this specification compressor on means that the motor driving the compressor is energized; and compressor off means that the motor driving the compressor is de-energized. In those systems where the passage of air over the evaporator is required. during compressor off cycles, for the purpose of defrosting the deposited frost, a time delay switch or timer must be provided to allow the evaporator fans to continue their full speed operation for the period immediately following the beginning of the compressor off-cycle that defrost would normally required. Then if the compressor off-cycle is extended beyond the period required for the normal defrost of the evaporator, the timer will cause the evaporator fan motor to be reconnected for low speed operation for the remainder of the compressor off-cycle which in fact may be of great duration, with consequent power savings.

It is important to notice here, the power savings which result from reduction of power input to the fan motors is only part of the power savings which occur to the user of the invention. The power input to the fan motors is part of the total heat input to the refrigerated space. The total compressor operating time must be sufficient to remove all the heat that has leaked into or been put into the cooler or freezer. The longer the operating time of the evaporator fan motors at full power, the longer some of the compressors must run in order to remove that heat. In a system maintaining a box at l0F every reduction of one watt in heat input to the box results in a power saving at the compressor of approximately 1 watt so that twice the number of watts saved at the evaporator are saved totally. It generally has been considered unwise to turn off the evaporator fan motors completely in freezers because the grease in the motor bearings has a tendency to harden. On restarting, the hardened grease lubricates poorly until it softens, which shortens bearing life, and because a stag nant air condition in the box may arise which generates uneven temperature conditions and, therefore, poor keeping qualities of the merchandise stored within the cooler or freezer. However, the high air flow which is required by evaporators for efficient heat transfer performance is not generally required by the refrigerator itself for the distribution of the coil air produced by these evaporators. In general, a much lesser air flow and air velocity is required for distribution of the cold air than is required for efficient operation of the evaporator. Therefore, the operation of the evaporator fans at speeds less than full, for instance at one'half speed, during those periods when the compressor is not operating, is entirely consistant with good refrigeration practice.

The speed change of the evaporator fan motors may be related to the on or off condition of the compressor; or the speed of the motors may instead be related to the condition of the initiating control (contactor; starter or switch; timer; temperature control; pressure control; or other). However, the relationship need not require instantaneous correspondence of conditions. Substantial delay in change of motor speed after change in control or compressor condition would still lie within the intent of the claims.

Techniques used for changing the speed of the fan motors could be: (a) the use of a motor which was inherently designed for single voltage operation but was usable at either of two speeds, depending on the connections made to its leads; (b) a motor which would operate at higher speed if a high voltage was applied to its terminals, and a lower speed if a low voltage was applied to its terminals; (b-l) the variation where the lower voltage was achieved by connecting in series with the power line to the motor an impedance, that is, a resistance or a reactance suchas a capacitance or inductance. which served to lower the voltage delivered to the motor below that of the supplyline; or (b-Z) where two different voltage supply lines were available, connecting the motor leads alternately to the higher voltage line and to the lower voltage line, in accord with the principles enumerated in this specification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a compression type refrigeration system cooling an insulated space using an electric motor driven compressor, a condenser, and an evaporator within the insulated space. The evaporator cools air blownover it by fans driven by motors capable of operating at high or low speed. The high or low speed conditions of the evaporator fan motors are determined by the position of a relay which serves to connect the evaporator fan motors to either a high voltage source or a low voltage source, depending on whether the compressor is operating or stationary.

FIG. 2 shows an modified electrical circuit for supplying high and low voltage power to evaporator fan motors. depending on the condition of a relay. When the relay is energized and its contacts are closed, high voltage power is delivered to the fan motor. When the relay coil is tie-energized, then the relay contacts are open. The current supplied to the motor is forced to traverse a choke which causes the voltage supply to the motor to be reduced, and thereupon to operate at a lower speed than when its supply of electricity came un-interruptedly from the electric supply means.

FIG. 3 shows the circuit diagram of a permanent split capacitor motor which is one of the types that are in general suitable for high voltage high speed; low voltage low speed operation of the type that is described in this specification, and in general is usable in the circuits and arrangements of FIGS. 1 & 2.

FIG. 4 shows a combined internal motor wiring diagram and a relay and power supply arrangement which includes a typical wiring diagram for a two speed motor, including an extended or tapped main winding and a relay which selects the low speed tap or lead of the motor when the relay is de-engerized and the high speed tap of the motor when the relay is energized.

FIG. 5 shows a simplified control arrangement utilizing a thermostat with a double throw contact which controls the ON/OFF operation of the compressor and simultaneously controls the evaporator motor voltage so that when the compressor is *ON" the evaporator motor is connected to high" voltage and runs at high speed, and when the compressor is OFF the evaporator motor is connected to low voltage and runs at low speed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows compressor 42 driven by motor 36 by way of shaft 38 and coupling 40. The compressor receives refrigerant vapor from suction line 65, and after compressing it to a pressure sufficiently high to condense in the condenser, discharges it to condenser coil 46 by discharge line 44. There it is condensed to a liquid by the cooling effect ofthe air which is drawn over the condenser coil 46 by fans 52 driven by motors 50. The liquid, resulting from the condensation of the refrigerant, flows through conduit 48 to receiver 54, wherein it collects as a pool 56. As needed this liquid refrigerant is delivered to -the' 'expansion valve 62 by way of dip tube 57 liquid line "58 and liquid line solenoid 60. The open or closed conditionof liquid solenoid 60 is determined by the condition of energization or de-energization 'ofits coil 60A.

The operation of the system to refrigerate or stop refrigerating is related to the open or closed condition of liquid solenoid valve 60 which condition is determined by thermostat 106 which monitors the temperature of the cooled space and turns on the system when the space gets warmer than desired. Sensing bulb 106A is in the cooled space. Bellows 106B expands as the bulb becomes warmer. The expansion of the bellows causes conducting bar 106C to make electrical contact between

terminals

106D and 106E. When

contacts

106D and 106E are made, solenoid coil 60A is energized, causing solenoid valve 60 to open. Conversely, the cooling of bulb 106A below its setting point causes bar 106C to move away from

contacts

106D and 106E, opening the circuit which supplies electricity to solenoid coil 60A causing solenoid coil 60A to become deenergized. This immediately results in solenoid 60 closing, preventing any further refrigerant liquid flow to the evaporator 66 from the receiver 54.

During the period that solenoid valve 60 is open refrigerant liquid from receiver 54 flows to evaporator 66 with its temperature and pressure reduced to the point where its refrigerating effect can be applied to the heat transfer element of the evaporator 66, because of the restricting effect of the expansion valve 62. In the heat transfer element of evaporator 66, the liquid refrigerant which has been supplied to it is evaporated to a vapor with its latent heat of evaporation supplied by the air blown across the heat transfer element by the fan 68A and 688, which are driven by the motors 70A and 708 respectively. The heat supplied from the air blown by the fans serves to cool the air for the overall effect of cooling the insulated space whose boundaries are established by insulated wall 122. When the refrigerant liquid supplied to the evaporator 66 has been completely evaporated, the resulting vapor is returned to the compressor 42 via suction line 65. In its return path, the cool vapor has its temperature monitored by bulb 62B of the expansion valve 62. If the vapor be comes too cool, which condition might result from expansion valve 62 being open more than necessary, resulting in a flow of liquid refrigerant through expansion valve 62 to the evaporator 66, which is more than the evaporator can evaporate. the over-cooled bulb 628 causes the valve elements to throttle the flow of refrigerant liquid to the evaporator 66.

Compressor 36 is supplied with power from three phase, four wire. alternating current network 2, comprising

lines

2A, 2B, 2C and N and in between any pair of 2A, 2B and 2C is a uniform alternating current single phase voltage whose phase differs from any other pair by The voltage from any one of

lines

2A, 2B or 2C to the neutral line N is equal to the value of the voltage between the

lines

2A, 2B or 2C or any of a pair of them divided by 1.732 3). For example, if power source 2 was a 208 volt three phase four wire network. the voltage between 2A or 2B and the voltage between 28 and 2C, and the voltage between 2C and 2A would be 208 volts, but the voltage between 2C and N and the voltage between 28 and N and the voltage 2A and N would be 208 volts divided by 1.732 (eg. V?) or 120 volts.

Motor 38 can be supplied with power only if the contactor whose contacts 26A. 26B and 26C control the flow of electricity from the power supply lines to the motor are closed. The condition of the contacts is determined by the energized or de-energized condition of the contactor coil 24.

The control circuit supplies power to the contactor coil (24) through

leads

4 and 6 which connect to

power lines

28 and 2C at points 2Cl and 2Bl. The control circuit for contactor magnetic coil 24 comprises supply line 6, fuse 8, wire 22 and control circuit contacts 20, l8, l6, l4, l2, l0 and supply line 4. The control contacts 10 through comprise switches including manual on-off switch 10, high pressure switch 12, low pressure switch 14, oil safety switch 16, motor winding temperature thermostat 18. motor current overload protector 20.

Specifically, the portion of the system related to the operation of the invention is as follows:

When the insulated room 122 is cold, thermostat contacts 106D and [06E are open. As a result, the solenoid coil 60A is tie-energized and the solenoid 60 is closed. In this condition, the compressor 42 operates to pump vapor out of suction line 65 and the evaporator 66 until the pressure therein drops to the setting of the low pressure switch 15 whose contacts 14 are in the control circuit of the compressor contactor. Then, the contacts 14 of the pressure switch open, deenergizing coil 24 of the compressor contactor causing its

contacts

26A, 26B and 26C to open, stopping the compressor. At the same time power is removed from contactor coil 24. power is also removed from relay coil 88. When this coil is de-energized, spring 86 urges clapper 84 upward so that contact 92 mates with and creates an electrical connection with stationary contact 94 establishing an electrical circuit for the flow of electricity between neutral wire N at terminal point N1 and power wire 2C at connection point 2C3. These connections provide a voltage for the operation of

fan motors

70A and 70B of 120V, roughly half of the normal 208V which is supplied to them for their full speed operation. At this reduced voltage, which is applied only when the compressor is stopped. the fans operate at essentially half speed and utilize essentially half the normal power.

As the temperature of the enclosed insulated space 122 gradually rises. the thermostat bulb 106A reacts by increasing the pressure in bellows 106B, forcing platen 106C against

contacts

106D and 106E, closing the circuit which allows electricity to be supplied to liquid solenoid coil 60A. When the contact is complete and power is supplied to solenoid coil 60A, liquid solenoid 60 opens, supplying refrigerant liquid from the receiver 54 through the expansion valve 62 to the evaporator 66, as described before. As the liquid reaches the evaporator, some of it flashes to vapor, raising the pressure in the evaporator and in the connecting suction pipe 65 which communicates with pressure switch 15. The pressure switch 15 senses the rise in pressure in the low side and when the rise is sufficient to reach its setting, contacts 14 close, supplying power to the compressor contactor coil 24 which causes the

contacts

26A, 26B and 26C to close. Simultaneously with the energization of contactor coil 24, relay coil 88 is energized, which causes platen 84 to be attracted to magnet core 90 with a force greater than can be resisted by return spring 86. The result of this motion is that the electrical circuit which had been formed between

contacts

92 and 94 is now broken and a new electrical contact between contacts 92 and96 is now made. This new electrical contact establishes a circuit between power wire 2B and connection point 2B3 and power wire 2C and connection point 2C3. Since the potential between these two wires is 220V, the voltage applied to motors A and 708 now is 220\/. It should be clear from the above description, therefore, that whenever compressor motor 36 is energized, causing the compressor to operate,

evaporator fans

70A and 70B will be energized with high voltage electricity, and when the compressor motor 36 is de-energized, causing it to stop,

evaporator fan motors

70A and 70B will be energized with low voltage electricity, causing them to run at approximately half speed with the significant power savings al ready described.

FIG. 2 shows one of the two evaporator fan motors, 70A, shown in FIG. 1, and a similar relay with a coil 88 with two wire leads 98 and 100, which are intended to be connected at points 102 & 104 on the leads to the compressor contactor 24, (FIG. 1). It is clear, therefore, that coil 88 will be energized when compressor contactor coil 24 is energized and will be d'e-energized when compressor contactor coil 24 is de-energized. During energized condition, power will be supplied directly to evaporator fan motor 70A from

power wires

28 and 2C allowing their full voltage to be imposed directly on the windings of the fan motor 70A. When the compressor stops and relay coil 88 is de-energized, the return spring 86 pulls the armature 84 away from the magnetic core 90, at the same time breaking the electrical circuit between

contacts

92 and 96. Now electricity from

power wires

28 and 2C must traverse both the motor and a voltage dropping reactor 83 which has leads 83A and 83B. This reactor can be selected for any voltage drop which would meet the needs of the user. The larger the voltage drop, the slower the fan motor 70A would operate, and the greater the power saving. The normal range of voltage reduction which the ordinary design engineer would select the reactor or choke 83 to produce, would be in the range of 25 to 60 percent of the full power supply voltage. In this case, reactor 83 has been selected to produce a voltage drop of approximately 50 percent so that the voltage on the motor 78 is 104V, a 50 percent reduction of the 208\/, which is the potential across the

power supply wires

28 and 2C. It is clear, then, from the description of the operation of this fan motor control circuit that, during those periods when the compressor operates, full voltage is applied to the evaporator fan motor for achieving full speed operation for maximum cooling effect. During those periods when the compressor is not operating, a reduced voltage, which is selectable in advance by the design engineer, is applied to the fan motor 70A with consequent reduction in power consumption and fan motor speed. If desired, a tapped reactor could be employed as shown in FIG. 2, where taps 83C and 83D are shown. The connection of wire 83A from its present position at the end of the reactor to position 83D would result in a reduced voltage drop and application, in turn, of the wire 83A to tap 83C would result in a still further reduction in the voltage drop which would be imposed on evaporator motor 70 during periods of compressor non-operation.

FIG. 3 shows the internal wiring diagram for a motor whose type is described as permanent split capacitor. This is a single phase alternating current motor which has no starting relay or starting switch but has a main winding 200, a phase winding 202, of a much higher resistance than the main winding, and a capacitor 204 in series with the phase winding. These components are designed and selected to produce the starting torque and operating speed and power for each application. These motors, in general have the characteristic that when reduced voltages are applied, reduced speeds and reduced power consumption occur. This is one of the motor types which can be employed evaporator fan motor 70A. Another type which can be so employed is the so-called shaded pole motor.

FIG. 4 shows the application of the concept of the in vention to a motor designated as a two-speed type. This motor has a main winding 200 and an extended main winding 206. In parallel across the main winding is the phase winding 202 in a series with its capacitor 204. The relay with its coil 88, with its

leads

98 and 100, is connected in exactly the same fasion as the relay coil with the same number in FIG. 1. When the contactor coil 24 is energized. coil 88 is energized, attracting clapper 84 against the force of return spring 86, so that contact 92 and contact 96 form an electrical circuit. In this mode. the motor operates at full speed in order to achieve full air flow and refrigerating effect at the evaporator. When the compressor contactor is deenergized, coil 88 is de-energized, and the return spring 86 draws clapper 84 upwards, breaking the circuit between

contacts

92 and 96 and making the circuit between 92 and 94. Application of the full line voltage to the extended winding 206 through lead 212 causes the motor to operate at a reduced speed, depending on the design of extended circuit 206. In this case, the extended winding is selected to provide a motor speed and a motor power consumption of approximately onehalf of that produced and consumed at the high speed condition.

In FIG. the thermostat comprising bulb 240, bellows 250, contact arm 252, cool contact 254, and warm contact 256 is so connected that when the bulb is exposed to a temperature lower than its setting, the contact arm 252 makes electrical contact with contact 254 completing the electrical circuit from power upply wire 28, wire 262, motor lead 76, motor 70A, motor lead 78, wire 260, wire 264, contact arm 252, cool contact 254, and wire 266 to neutral conductor N. The connection from wire 2B to N provides a low voltage power supply to motor 70A which is designed for full speed operation at 208 volts but operates at lower speed at lower voltage. The motor 36 of the compressor, which is designed for full speed operation at 120 volts, has both leads connected to power supply wire N, one by wire 272, the second by

wires

258, 264, contact carrier 252, cool contact 254, and wire 266, and therefore does not run, having zero voltage across its leads. When the cooled space warms, the expandable fluid in bulb 240 causes the bellows 250 to move contact arm 252 in a direction which causes it to break contact with contact 254 and make contact with contact 256. In this state, power supply wire 2C supplies power through wire 268, contact 256 and contact arm 254 and wire 264 to wire 260 and to lead 78 of fan motor A. The other lead 76 of the fan motor is connected to power supply wire 28 which in cooperation with supply wire 2C provides full voltage of 208 across the fan motor for its full speed operation. The compressor motor now has lead 272 as before connected to N. lts other lead 258 now is connected to power supply wire 2C by way of wire 264, contact arm 252, contact 256 and wire 268. This provides 120 volts across the compressor motor, which causes it to operate normally. Thus, with one control and switch we have established on-off control of the compressor and corresponding high-low speed control of the evaporator fan.

I claim:

1. An improved refrigeration system having conduit connected compressor, condenser (46), restrictor (62), and evaporator (66); first motor (36) connected to the compressor for driving it, said first motor having energized and deenergized conditions; a fan (68A), positioned to blow air over the evaporator (66); a second motor (70A) connected to said fan for driving it, said second motor adapted to operate at higher voltagehigher speed, lower voltage-lower speed; first conductor means (82) connected to said second motor for supplying electric power to it; wherein the improvement comprises; second conductor means adapted for connection to a higher voltage power supply (2B3); third impedance-free conductor means adapted for connection to a lower voltage power supply (N1); switch means (92, 94, 96) connected to first conductor means (82), second conductor means (97) and third conductor means (95), adapted to provide electrical contact between said first conductor means (82) and alternately second conductor means (97) and third conductor means (95), said switch means (92, 94, 96) being operatively connected to establish essential correspondence between a. the energized condition of the first motor (36) and the electrical contact between the first conductor means (82) and the second conductor means (97) to cause the second motor to operate at higher speed, and b. the deenergized condition of the first motor (36) and electrical contact between the first conductor means (82) and the third conductor means (95) to cause the second motor to operate at lower speed.

l= l l

Claims

1. An improved refrigeration system having conduit connected compressor, condenser (46), restrictor (62), and evaporator (66); first motor (36) connected to the compressor for driving it, said first motor having energized and deenergized conditions; a fan (68A), positioned to blow air over the evaporator (66); a second motor (70A) connected to said fan for driving it, said second motor adapted to operate at higher voltage-higher speed, lower voltage-lower speed; first conductor means (82) connected to said second motor for supplying electric power to it; wherein the improvement comprises; second conductor means (97) adapted for connection to a higher voltage power supply (2B3); third impedance-free conductor means (95) adapted for connection to a lower voltage power supply (N1); switch means (92, 94, 96) connected to first conductor means (82), second conductor means (97) and third conductor means (95), adapted to provide electrical contact between said first conductor means (82) and alternately second conductor means (97) and third conductor means (95), said switch means (92, 94, 96) being operatively connected to establish essential correspondence between a. the energized condition of the first motor (36) and the electrical contact between the first conductor means (82) and the second conductor means (97) to cause the second motor to operate at higher speed, and b. the deenergized condition of the first motor (36) and electrical contact between the first conductor means (82) and the third conductor means (95) to cause the second motor to operate at lower speed.