Refrigeration – Gas compression – heat regeneration and expansion – e.g.,...
Reexamination Certificate
2002-10-29
2004-04-06
Esquivel, Denise L. (Department: 3744)
Refrigeration
Gas compression, heat regeneration and expansion, e.g.,...
C062S228100
Reexamination Certificate
active
06715301
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reciprocating compressor for a refrigerator using a linear motor, and particularly, to an apparatus and a method for controlling a driving of the reciprocating compressor for a refrigerator using a linear motor in which capacitance is varied according to a variation of a driving load, thereby improving a driving efficiency of a compressor.
2. Description of the Background Art
As well-known, a compressor compresses a refrigerant circulated in a cooling apparatus such as an air conditioner and a refrigerator into a high temperature and high pressure. The compressor includes a reciprocating compressor, a rotary compressor, a brushless direct current (BLDC) compressor, and an ability variable-type reciprocating compressor called as an inverter compressor and having a varied rotary speed.
The reciprocating compressor using a linear motor varies a piston stroke thereof according to a voltage applied to a motor, thereby controlling a cooling capacity by a user's intention.
The reciprocating compressor will be explained with attached drawings.
FIG. 1
shows an apparatus for controlling a driving of a general reciprocating compressor.
Referring to
FIG. 1
, an apparatus for controlling a driving of a reciprocating compressor comprises a reciprocating compressor
100
for controlling a cooling capacity by varying a stroke of an inner piston by a voltage input to an inner motor M according to a stroke reference value set by a user: a voltage detecting unit
102
for detecting a motor voltage applied to the reciprocating compressor
100
by varying the piston stroke of the reciprocating compressor
100
; a current detecting unit
104
for detecting current applied to the reciprocating compressor
100
by varying the piston stroke of the reciprocating compressor
100
; a microcomputer
106
for calculating a stroke value by using detected voltage and current from the voltage detecting unit
102
and the current detecting unit
104
, comparing the calculated stroke value with the stroke reference value, then outputting a switching control signal according to the comparison between the calculated stroke value and the stroke reference value; and an electric circuit unit
108
for controlling a size of the motor voltage applied to the reciprocating compressor
100
according to interrupting an AC power source to a triac Tr
1
controlled by a switching control signal of the microcomputer
106
.
Operations for controlling a driving of the general reciprocating compressor will be explained.
The reciprocating compressor
100
controls a cooling capacity by a varied piston stroke, wherein the piston reciprocates up and down by the motor voltage input from the motor according to the stroke reference value set by a user.
The stroke means a distance that a piston in the reciprocating compressor
100
moves with reciprocation.
A period of turn-on of the triac Tr
1
in the electric circuit unit
108
becomes long by a control signal of the microcomputer
106
, so that a stroke is increased. At this time, the voltage detecting unit
102
and the current detecting unit
104
respectively detect voltage and current applied to the reciprocating compressor
100
, and output the detected voltage and current to the microcomputer
106
.
The microcomputer
106
calculates a stroke by using voltage and current detected from the voltage detecting unit
102
and the current detecting unit
104
, compares the calculated stroke with a stroke reference value set by a user, and outputs a switching control signal to the triac Tr
1
according to the comparison between the calculated stroke and the stroke reference value.
That is, when the calculated stroke is smaller than the stroke reference value, the microcomputer
106
outputs the switching control signal which lengthens the period of turn-on of the triac Tr
1
, thereby increasing a voltage applied to the reciprocating compressor
100
.
In the meantime, when the calculated stroke is greater than the stroke reference value, the microcomputer
106
outputs the switching control signal which shortens the period of turn-on of the triac Tr
1
, thereby decreasing a voltage applied to the reciprocating compressor
100
.
A relation between a voltage (V) applied to a motor (M) of the reciprocating compressor
100
and a stroke will be shown as follows.
V
=
L
ⅆ
i
ⅆ
t
+
R
i
+
α
ω
S
ω
=
2
π
f
[
Equation
1
]
Wherein, &agr; indicates a motor constant for converting electric force into mechanical force, S indicates stroke, R indicates inner resistance of a motor, and L indicates inductance of a motor (M).
As shown in the equation 1, inductance voltage
(
L
ⅆ
i
ⅆ
t
)
is almost similar to counter-electromotive force (&agr;&ohgr;S), and voltage (Ri) of inner resistance (R) of the reciprocating compressor
100
is a small value possible to ignore when compared with the
(
L
ⅆ
i
ⅆ
t
)
and the counter-electromotive force (&agr;&ohgr;S).
Therefore, voltage (V) applied to the motor (M) is determined by a sum of the inductance voltage
(
L
ⅆ
i
ⅆ
t
)
and the counter-electromotive force (&agr;&ohgr;S).
Accordingly, to get a greater stroke in the reciprocating compressor, voltage applied to the motor has to be great.
To improve efficiency of the reciprocating compressor, inductance value of a coil wound on the motor has to be small.
That is, as shown in
FIG. 2
, capacitor (C) is connected to the motor (M) in series and attenuates an inductance (L) of a coil wound on the motor, thereby improving efficiency of the reciprocating compressor.
FIG. 2
is a block diagram of a reciprocating compressor in accordance with the conventional art.
Referring to
FIG. 2
, an operation for attenuating inductance of the coil will be explained. Voltage applied to the motor and both ends of the capacitor is shown as a following equation.
V
=
L
ⅆ
i
ⅆ
t
+
1
C
∫
i
ⅆ
t
+
R
i
+
α
ω
S
[
Equation
2
]
At this time, capacitance (C) is shown as a following equation.
C
=
1
(
2
π
f
)
2
L
[
Equation
3
]
Wherein, the capacitance (C) and the inductance (L) are predetermined as resonant values.
Accordingly, the capacitance (C) and the inductance (L) are attenuated by being resonated each other, so that voltage applied to the motor (M) and both ends of the capacitor is shown as a following equation.
V=Ri+&agr;&ohgr;s
[Equation 4]
As shown in the equation 4, the applied voltage (V) has a similar size as the counter-electromotive force (&agr;&ohgr;S) because the inductance voltage
(
L
ⅆ
i
ⅆ
t
)
and capacitor voltage
(
1
C
∫
i
ⅆ
t
)
are attenuated after being resonated each other. Therefore, the reciprocating compressor can obtain a necessary stroke with just a low voltage (V).
Also, because the capacitor voltage
(
1
C
∫
i
ⅆ
t
)
is applied to the motor (M) together with the applied voltage (V) applied to the motor and both ends of the capacitor, a great stroke can be obtained with a low voltage, thereby improving a corresponding capacity to overload.
In case of that the conventional-art reciprocating compressor is adopted to a refrigerator and driven, necessary voltage for the motor (M) of the reciprocating compressor
100
to obtain a constant stroke becomes different according to a driving load of a refrigerator.
That is, the motor M of the reciprocating compressor
100
requires voltage greater than line voltage (in Korea, AC 220) when the driving load of a refrigerator is greater, and requires voltage smaller than line voltage when the driving load of a refrigerator is smaller.
Accordingly, the microcomputer
106
, in case that the driving load of a refrigerator is great, shortens off-
Drake Malik N.
Esquivel Denise L.
Fleshner & Kim LLP
LG Electronics Inc.
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