Background Art Generally, a compressor is a device that compresses refrigerant using a rotating force of an internal motor, and is used in a refrigerator, air conditioner, etc.

Especially, as shown in FIG. 1, a motor for a compressor applied in a refrigerator is composed of a stator and a rotor, and can perform only a normal operation (for example, rotation of 3600rpm) though there is a difference according to the characteristic of the product.

Meanwhile, the representative operation mode of the refrigerator is classified into a quick operation mode and a standard operation mode. Actually, the time when the refrigerator operates in the quick operation mode is less than 10% of the real use time of the refrigerator, and during other time, the refrigerator operates in the standard operation mode.

Conventionally, in the standard operation mode, the temperature width to be adjusted is not so large. However, in the quick operation mode, the temperature width to be adjusted is large, and thus a quick cooling is performed by driving the motor at a fixed speed, i. e., at a high

speed. This high-speed operation exerts a bad effect on the refrigerator such as generation of noise, increase of power consumption, strain on the product, etc.

Nevertheless, the compressor motor of the refrigerator, irrespective of the operation mode, operates at a high speed to match the quick cooling mode.

As shown in FIG. 2, the conventional compressor motor is driven at a single speed. That is, in case of the quick operation mode, the duty rate of the motor is set as 1', and the compressor motor is continuously driven irrespective of the temperature condition of the refrigerator.

In case of the standard operation mode, the compressor motor is driven to repeat an on/off operation according to a proper duty rate so that the refrigerator maintains its set temperature according to the temperature condition of the refrigerator. At this time, the load of the motor in the quick operation mode is greater than that in the standard operation mode.

As described above, since the conventional motor for the compressor is driven at the high speed irrespective of the operation mode, it has a large power consumption, and generates much noise during operation. Also, the product may be damaged due to the frequent on/off operation of the motor, and this causes the life span of the product to be shortened.

Disclosure of the Invention

Therefore, an object of the present invention is to solve the problems involved in the prior art and to provide a pole-change type motor that can vary the speed of the motor to provide a variable-speed operation system.

In order to accomplish the above-mentioned object, the present invention provides a pole-change type motor comprising a rotor, a stator for generating a torque of the rotor so as to perform a high-speed or low-speed operation through a pole change, and a relay section for controlling the pole change of the stator.

Brief Description of the Drawings The above object, other features and advantages of the present invention will become more apparent by describing the preferred embodiment thereof with reference to the accompanying drawings, in which: FIG. 1 is a view illustrating a conventional motor for a compressor.

FIG. 2 is a graph illustrating an operation state of a conventional motor for a compressor.

FIG. 3 is a view illustrating a pole-change type motor for a compressor according to the present invention.

FIG. 4 is a view illustrating the structure and winding arrangement of a pole-change type motor according to the present invention.

FIG. 5 is a circuit diagram of a control section of a pole-change type motor according to the present invention.

FIG. 6 is a view illustrating a wiring state of a two-pole operation of the motor according to the present invention.

FIG. 7 is a view illustrating a magnet field distribution of a two-pole operation of the motor according to the present invention.

FIG. 8 is a graph illustrating an abnormal magnetic field distribution of a main winding and compensation for an abnormal magnetic field distribution effected by compensation windings according to the present invention.

FIG. 9 is a view illustrating a wiring state of a four-pole operation of the motor according to the present invention.

FIG. 10 is a view illustrating a magnet field distribution of a four-pole operation of the motor according to the present invention.

Best Mode for Carrying Out the Invention Now, the pole-change type motor according to a preferred embodiment of the present invention will be described in detail with reference to the annexed drawings.

FIG. 3 is a view illustrating a pole-change type motor for a compressor according to the present invention, FIG. 4 is a view illustrating the structure and winding arrangement of a pole-change type motor according to the present invention, and FIG. 5 is a circuit diagram of a control section of a pole-change type motor according to the present invention.

Also, FIG. 6 is a view illustrating a wiring state of a two-pole operation of the motor according to the present invention, FIG. 7 is a view illustrating a magnet field distribution of a two-pole operation of the motor according to the present invention, and FIG. 8 is a graph illustrating an abnormal magnetic field distribution of a main winding and compensation for an abnormal magnetic field distribution effected by compensation windings according to the present invention.

Also, FIG. 9 is a view illustrating a wiring state of a four-pole operation of the motor according to the present invention, and FIG. 10 is a view illustrating a magnet field distribution of a four-pole operation of the motor according to the present invention.

As shown in FIG. 3, the pole-change type motor according to the present invention includes a rotor (reference numeral omitted), a stator (reference numeral omitted) for generating a torque of the rotor so as to perform a high-speed or low-speed operation through a pole change (i. e., from the two-pole type to the four-pole type and vice versa), and a relay section (not illustrated) for controlling the pole change of the stator.

The stator, as shown in FIG. 4, includes first to fourth main windings M1~M4 for generating the torque of the rotor by two poles or four poles, first to fourth auxiliary windings S1~S4 for generating a start torque and a rotative torque by supplying a magnetic flux orthogonal to a magnetic flux generated by the first to fourth main windings M1~M4, and first and second compensation windings

Cl and C2 for compensating for a magnetic flux distortion generated between the same poles of the first to fourth main windings M1~M4 during a two-pole operation.

Also, in order to variably adjust the speed of the motor at a low or high speed, the relay section changes polarities of the first to fourth main windings M1~M4 and the first to fourth auxiliary windings S1~S4 to the two poles or four poles, and switches the connection state of the first and second compensation windings Cl and C2.

At this time, the relay section includes a first relay section RY1 for switching to control the on/off operation of the motor, a second relay section RY2 for switching to change the polarity by changing wiring of the first to fourth main windings M1~M4, a third relay section RY3 for switching to change the polarity by changing wiring of the first to fourth auxiliary windings S1~S4, and first and second compensation windings Cl and C2, and a fourth relay section RY4 for switching to change wiring of capacitors during the four-pole operation according to the switching of the third relay section RY3.

According to the present invention, the relay section operates in association with a temperature sensor, and if the quick operation is required according to a result of temperature sensing, the relay section controls all the relay sections to switch over to the two-pole termination so that the motor operates with the two poles.

On the contrary, if the load is reduced due to the two-pole operation and thus the quick operation is not required, the relay section controls the relay sections to

switch over to the four-pole termination so that the motor operates with the four poles.

The operation of the pole-change type motor according to the present invention as constructed above will now be explained.

First, the operation of the motor in the quick operation mode is as follows.

Referring to FIG. 5, the first relay section RY1 is turned on, and the second and the third relay sections RY2 and RY3 switch over to the two-pole termination, respectively. At this time, if the third relay section RY3 switches over to the two-pole termination, the power is supplied to the first and second compensation windings Cl and C2, which are connected between the adjacent windings of the same polarity among the first to fourth main windings M1~M4.

During the two-pole operation, the wiring state of the first to fourth main windings M1~M4 and the first and second compensation windings Cl and C2 is illustrated in FIG. 6.

In this state, the rotor starts to rotate by the start torque of the first to fourth main windings M1~M4 generated by the power supply, and the motor is driven by the first to fourth main windings M1~M4 and the first and second compensation windings Cl and C2 at a high speed with the two poles.

At this time, the windings adjacent to each other among the first to fourth main windings MI-M4 have the same polarity. For example, the first and second main

windings M1 and M2 have the N pole, and the third and fourth main windings M3 and M4 have the S pole. FIG. 7 shows the magnetic field distribution during the two-pole operation.

Because of the above-described magnetic field distribution, there occurs an abnormal phenomenon of a space magnetic flux distribution that the S pole is compulsorily created between the first and second main windings M1 and M2. In this case, since the first compensation windings Cl adjacent to the first and second windings M1 and M2 has the N pole, the S pole component of the first and second main windings M1 and M2 is offset to compensate for the abnormal phenomenon of the space magnetic flux distribution.

In the same manner, an abnormal phenomenon of a space magnetic flux distribution generated between the third and fourth main windings M3 and M4 is compensated for by the polarity of the second compensation winding C2.

With reference to the graph of FIG. 8, the abnormal phenomenon of the space magnetic flux distribution generated between the first and second main windings M1 and M2 or between the third and fourth main windings M3 and M4 during the two-pole operation, i. e., a distortion phenomenon that the magnetic flux is rapidly reduced between sixth and seventh slots or between 18th and 19th slots.

Accordingly, in order to compensate for the abnormal sine-wave magnetic flux due to the distortion phenomenon, the magnetic flux of the first to fourth main windings

M1~M4 and the magnetic flux of the first and second compensation windings Cl and C2 are combined to produce a combined sine-wave magnetic flux, and this causes the efficiency and noise characteristics to be improved.

Here, the first and second compensation windings Cl and C2 are connected in parallel to the first to fourth main windings M1~M4 in case that the output torque is large, while they are connected in series to the first to fourth main windings M1~M4 in case that the output torque is small.

During the quick operation, i. e., the two-pole operation, if it is detected that the quick operation is not required through the temperature sensing by the temperature sensor, the quick operation should switch over to the standard operation.

Here, the operation of the motor in the standard operation mode is as follows.

Referring to FIG. 5, the first relay section RY1 is turned on, and the second and the third relay sections RY2 and RY3 switch over to the four-pole termination, respectively.

At this time, if the third relay section RY3 switches over to the four-pole termination, the power is supplied to the first to fourth auxiliary windings S1~S4, and the connection between the first and second compensation windings Cl and C2 and the first to fourth main windings M1~M4 is released.

During the four-pole operation, the wiring state of the first to fourth main windings M1~M4 and the first to fourth auxiliary windings S1~S4 is illustrated in FIG. 6.

In this state, the rotor starts to rotate by the start torque of the first to fourth main windings M1~M4 generated by the power supply, and the motor is driven by the first to fourth main windings M1~M4 and the first to fourth auxiliary windings Sl-S4 at a low speed with the four poles.

At this time, as shown in FIG. 10, the mechanical position of the first to fourth auxiliary windings S1~S4 is displaced by 90° and the phase thereof is shifted by 90° with respect to the first to fourth main windings M1~M4 to form the four poles.

Also, during the four-pole operation of the motor, the windings adjacent to each other among the first to fourth main windings M1~M4 have the polarity opposite to each other. For example, as shown in FIG. 10, the first and third main windings MI and M3 have the N pole, and the second and fourth main windings M2 and M4 have the S pole, so that the abnormal phenomenon of the space magnetic flux distribution does not occur between the main windings.

Accordingly, during the standard operation where the motor operates by four poles, the connection of the first and second compensation windings Cl and C2 is released.

Also, according to the present invention, the connection and release of a starting capacitor Cs connected to the first auxiliary windings S1 is controlled through the fourth relay section RY4.

Specifically, in order to increase the start torque of the rotor for a predetermined time through the fourth relay section RY4, the starting capacitor Cs is connected in parallel to the operation capacitor Cr, and if the predetermined time elapses, the fourth relay section RY4 is turned off.

At this time, while the specified wiring form of the first to fourth main windings Ml-M4 and the first and second compensation windings Cl and C2, and of the first to fourth main windings M1~M4 and the first to fourth auxiliary windings S1~S4 have been described and illustrated with reference to the preferred embodiment of the present invention, it will be apparent that various changes in form and details may be made therein as needed in circuit design.

Industrial Applicability As apparent from the above description, the pole- change type motor according to the present invention has the effects that if the quick operation is needed, the motor switches over to the two-pole type and operates at the high speed to achieve the quick cooling, while if the standard operation becomes possible with the lapse of the predetermined time, the motor switches over to the four- pole type and operates at the low speed to achieve an effective cooling.