COMPRESSOR MOTOR CONTROL CIRCUIT

[0001] The present invention relates to an electronic control circuit that controls the operation of the compressor motor used in cooling devices.

[0002] In single-phase induction motors, for example in compressor motor (M') control circuit (V) used in cooling devices, auxiliary and main windings (W1 , W2) are situated and, by energizing the auxiliary winding (W1), start of the motor and by energizing the main winding (W2), constant operation of the motor is provided (Figure 1). By the auxiliary winding being fed through a capacitor (C1) connected in series in the control of a relay (R), the start of the motor is improved; however, this capacitor (C1), through which the auxiliary winding (W1) is fed, cannot compensate the reactive power drawn from the AC power source by the compressor motor (M') and in some embodiments, by other electrical loads (Y') such as fan, defrost and illumination element located in cooling devices along with the compressor motor (M'). In other words, the capacitor (C1) connected in series to the auxiliary winding (W1) alone do not correct the power factor of the total load that is defined as the ratio of actual power to apparent power. In the constant operation following the start, a second capacitor (C2) connected in parallel to the AC power source input is used in the control circuit for the total power factor correction of the compressor motor (M') and the other electrical loads in the cooling device. The second capacitor (C2) only corrects the power factor; however, this capacitor (C2) does not benefit the start of the motor (M').

[0003] In the Patent No JP57135692, in a single-phase induction motor, a starting circuit is explained which activates the capacitor after the start and corrects the power factor of the motor during operation.

[0004] The aim of the present invention is the realization of a low-cost control circuit that improves the start of the compressor motor and corrects the power factor in the constant operation.

[0005] The control circuit realized in order to attain the aim of the present invention is explicated in the claims.

[0006] The compressor motor used in cooling devices, for example in refrigerators, is controlled by the electronic control circuit of the present invention.

[0007] The control circuit comprises a capacitor providing the start to be improved and power factor correction by compensating the reactive power drawn by the main and the auxiliary windings of the compressor motor from the AC power source, and a relay at the output of the capacitor providing the current to be directed to the auxiliary winding or to the main winding.

[0008] In the control circuit of the present invention, the capacitor is connected between the power line and the common contact of the relay. The first contact of the relay is connected to the auxiliary winding and the second contact of the relay is connected to the power line, hence to the main winding of the motor connected in series to the power line.

[0009] In its first position, the relay provides the auxiliary winding to be activated by joining the common contact and the first contact, the capacitor to be connected in series to the auxiliary winding and thus, the auxiliary winding to be fed through the capacitor.

[0010] In its second position, the relay provides the capacitor to be connected in parallel to the power input between the power lines by joining the common contact and the second contact, the auxiliary winding to be deactivated and the main winding to be fed through the capacitor.

[0011] In an embodiment of the present invention, the relay is time delay current type and in its first position, provides the first contact to remain closed until the end of a time period predetermined for the start of the compressor motor and during this time period, provides the auxiliary winding to be fed through the capacitor and improves the start of the compressor motor. In its second position, at the end of the determined time period, the time delay current type relay both deactivates the auxiliary winding by opening the first contact and provides the main winding to be fed through the capacitor by closing the second contact.

[0012] In an embodiment of the present invention, along with the operation of the compressor motor, the control circuit also controls the operation of other electrical loads such as fan, defrost heater and illumination element in the cooling device wherein the compressor motor is used. The other electrical loads in the cooling device are connected in series to the power line together with the main winding of the motor and in the first position of the relay, are fed directly from the power line without capacitor together with the main winding, whereas in the second position of the relay, are fed through the capacitor and thus, the power factors are corrected.

[0013] In the control circuit of the present invention, by the function of two capacitors being performed by a single capacitor, both the start of the compressor motor is improved and the power factor of the compressor motor and of the other electrical loads in the cooling device, wherein the compressor is used, is corrected. The relay directing the capacitor output to the auxiliary winding or to the main winding, at the same time, provides the auxiliary winding to be deactivated, in a way, performs the function of two relays alone. Since the auxiliary winding is active during the start and completely deactivated afterwards, it is designed such that it will compensate only the momentum during the start, less winding wire is used and thus, cost advantage is provided.

[0014] The control circuit realized in order to attain the aim of the present invention is illustrated in the attached figures, where:

[0015] Figure 1 - is the schematic view of a compressor motor control circuit

[0016] in the prior art.

[0017] Figure 2 - is the schematic view of the compressor motor control circuit of the present invention.

[0018] The elements illustrated in the figures are numbered as follows:

[0019] Control circuit

[0020] 2 - Power line

[0021] 3 - Auxiliary winding

[0022] 4 - Main winding

[0023] 5 - Capacitor

[0024] 6 - Relay

[0025] 7 - Switching contact

[0026] 8 - Common contact

[0027] 9 - First contact

[0028] 10 - Second contact [0029] 11 - Relay coil

[0030] The control circuit (1) of the present invention is suitable to be used for the electronic control of the compressor motor (M) in cooling devices, for example in refrigerators.

[0031] The control circuit (1) comprises a power line (2) providing the energy that is received from the AC power source by means of the power input (L, N) named as "phase and neutral" to be transmitted, an auxiliary winding (3) located in the compressor motor (M) and providing the rotor to be rotated by forming a magnetic field when voltage is applied to the compressor motor (M) from the AC power source, forming a magnetic field for the torque that is required at the start, a main winding (4) connected in series to the power line (2) and forming the magnetic field that is required for constant operation, a capacitor (5) providing the start of the compressor motor (M) to be improved and power factor correction by compensating the reactive power drawn by the auxiliary and the main windings (3, 4) from the AC power source, and a relay (6) providing the current to be directed.

[0032] The relay (6) comprises a switching contact (7) moving when current flows there through and the applied current is cut off, thus, providing current transmission between the desired points, a relay coil (11) moving the switching contact (7) by forming a magnetic field when current is applied, a common contact (8) whereto the fixed end of the switching contact (7) is connected, a "normally closed" first contact (9) being closed in the first position (I) of the relay (6) and open in its second position (II), and a "normally open" second contact (10) being open in the first position (I) of the relay (6) and closed in its second position (II). In the first position (I) of the relay (6), the switching contact (7) contacts the first contact (9) and in the second position (II) of the relay (6), the switching contact (7) contacts the second contact (10).

[0033] The control circuit (1) of the present invention comprises

[0034] - a capacitor (5) connected between the power line (2) and the common contact (8) of the relay (6)

[0035] and [0036] - a relay (6), the first contact (9) of which is connected to the auxiliary winding (3) and the second contact (10) of which is connected to the power line (2) whereto the main winding (4) is connected in series,

[0037] - which, in its first position (I), provides the auxiliary winding (3) to be activated by joining the common contact (8) and the first contact (9), and the auxiliary winding (3) to be fed through the capacitor (5) by the capacitor (5) being connected in series to the auxiliary winding (3),

[0038] - which, in its second position (II), provides the capacitor (5) to be connected in parallel to the power input (L, N), the main winding (4) to be fed through the capacitor (5) and the auxiliary winding (3) to be deactivated by joining the common contact (8) and the second contact (10).

[0039] In the control circuit (1) of the present invention, the capacitor (5) improves the start of the compressor motor (M) in the first position (I) of the relay (6) and provides power factor correction in the second position (II) of the relay (6).

[0040] In an embodiment of the present invention, the relay (6) is time delay current type and in its first position (I), provides the first contact (9) to remain closed until the end of a time period (T) predetermined for the start of the compressor motor (M) and during this time period (T), provides the auxiliary winding (3) to be fed through the capacitor (5) and improves the start of the compressor motor (M).

[0041] In its second position (II), at the end of the determined time period (T), the time delay current type relay (6) both deactivates the auxiliary winding (3) by opening the first contact (9) by the effect of the current flowing through the relay coil (11) and provides the main winding (4) to be fed through the capacitor (5) that becomes connected in parallel to the power input (L, N), and corrects the total power factor by closing the second contact (10).

[0042] In another embodiment of the present invention, along with the operation of the compressor motor (M), the control circuit (1) also controls the operation of other electrical loads (Y) such as fan, defrost heater and illumination element in the cooling device wherein the compressor motor (M) is used. The other electrical loads (Y) in the cooling device are connected in series to the power line (2) together with the main winding (4) and in the first position (I) of the relay (6), are fed directly from the power line (2) (without capacitor) together with the main winding (4), whereas in the second position (II) of the relay (6), are fed through the capacitor (5) and thus, the power factors are corrected. The compressor motor (M) is a single-phase induction motor and in the control circuit (1), during the start, the auxiliary winding (3) and the main winding (4) are activated together. In order that the start is performed as desired, the capacitor (5) remains connected in series to the auxiliary winding (3) throughout the predetermined time period (T). This kind of connection is provided by the un energized contact positions of the time delay current type relay (6). Before energizing the compressor motor (M), the common contact (8) and the first contact (9) of the relay (6) are in a joint position and the relay coil (11) is connected in series to the main winding (4). When the compressor motor (M) is energized from the power input (L, N), the relay coil (11) is stimulated by the current being transmitted through the power line (2) and flowing through the main winding (4), and at the end of a predetermined time period (T), the connection of the common contact (8) of the relay (6) with the first contact (9) is cut off and the common contact (8) joins the second contact (10). Thus, after sufficient time (T) has passed in order that the compressor motor (M) can start, both the auxiliary winding (3) is deactivated and the capacitor (5) is provided to be connected in parallel to the power input (L, N). By the capacitor (5) being connected in parallel to the power input (L, N), the reactive power being drawn during operation from the AC power source by all other electrical loads (Y) that are connected to the control circuit (1), is drawn through the capacitor (5) and the power factor in constant operation is corrected. In the situation that the energy coming from the power input (L, N) is cut off or a safety element such as thermal protector cuts off the circuit, the energy of the relay (6) is cut off and the contacts (8, 9, 10) return to their prior situation, that is, the common contact (8) and the first contact (9) pass to the joint position. Thus, the compressor motor (M) gets ready to start again. [0044] In the embodiment of the present invention, by the function of two capacitors being performed by a single capacitor (5), both the start of the compressor motor (M) is improved and the power factor of the compressor motor (M) and of the other electrical loads (Y) in the cooling device is corrected. While in known embodiments, a relay or an element such as PTC functioning as relay is used to activate or deactivate the auxiliary winding, in the embodiment of the present invention, the relay (6) directing the capacitor (5) output to the auxiliary winding (3) or to the main winding (4), at the same time, provides the auxiliary winding (3) to be deactivated, in a way, performs the function of two relays alone. In known embodiments, since the auxiliary winding remains active in constant operation after the start, the winding design has to be made suitable for both start and constant operation conditions, whereas in the control circuit (1) of the present invention, since the auxiliary winding (3) is active during the start and completely deactivated afterwards, it is designed such that it will compensate only the momentum during the start, less winding wire is used and thus, cost advantage is provided.

[0045] It is to be understood that the present invention is not limited by the embodiments disclosed above and a person skilled in the art can easily introduce different embodiments. These should be considered within the scope of the protection postulated by the claims of the present invention.