U.S. patent number 3,877,243 [Application Number 05/401,265] was granted by the patent office on 1975-04-15 for refrigeration systems including evaporator with 2 speed fan motor.
Invention is credited to Daniel E. Kramer.
United States Patent |
3,877,243 |
Kramer |
April 15, 1975 |
REFRIGERATION SYSTEMS INCLUDING EVAPORATOR WITH 2 SPEED FAN
MOTOR
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.
Inventors: |
Kramer; Daniel E. (Yardley,
PA) |
Family
ID: |
23587045 |
Appl.
No.: |
05/401,265 |
Filed: |
September 27, 1973 |
Current U.S.
Class: |
62/180; 62/186;
62/183; 62/187 |
Current CPC
Class: |
F25B
49/02 (20130101); Y02B 30/70 (20130101); F25B
2600/112 (20130101) |
Current International
Class: |
F25B
49/02 (20060101); F25d 017/00 () |
Field of
Search: |
;62/180,186,181,183 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wye; William J.
Claims
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 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.
Description
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 of cooling 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.degree. and
32.degree., the practice of leaving the evaporator fans running has
some basis because the frost that is deposited on the surfaces of
the refrigerating coil during those periods that the compressor is
operating is defrosted by the passage of air warmer than 32.degree.
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 widespread,
and increasing shortage of the fossil fuels used 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 -10.degree.F 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 stagnant 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-1) 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 such as a
capacitance or inductance, which served to lower the voltage
delivered to the motor below that of the supply line; or (b-2)
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 blown over 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 de-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 of the 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 condition of liquid solenoid 60 is
determined by the condition of energization or de-energization of
its 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 de-energized.
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 68B, which are driven by the motors 70A
and 70B 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 becomes 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 62B 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 120.degree.. 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
(.sqroot.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 2B and 2C, and the voltage between 2C and 2A would
be 208 volts, but the voltage between 2C and N and the voltage
between 2B and N and the voltage 2A and N would be 208 volts
divided by 1.732 (eg. .sqroot.3) 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 2B 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, 18, 16, 14, 12, 10 and supply line 4. The control
contacts 10 through 20 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
106E are open. As a result, the solenoid coil 60A is de-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, de-energizing 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 and 96 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 70A and 70B now is 220V. 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 already 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 de-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 2B 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 2B 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 208V, which is the
potential across the power supply wires 2B 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 as 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 invention 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 de-energized, 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 one-half of that produced and consumed at the high
speed condition.
In FIG. 5 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 2B,
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 70A. The other lead 76 of the fan motor is
connected to power supply wire 2B 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. Its 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.
* * * * *