JP2020129959A - Electric motor and compressor - Google Patents

Abstract

To provide a compressor which still has a satisfactory demagnetization resistance even if an amount of Dy(dysprosium) that a rare earth magnet used in an electric motor contains is reduced.SOLUTION: An electric motor according to the present invention is a permanent magnet-embedded type electric motor in which flat plate-shaped permanent magnets are embedded along a peripheral edge of a cylindrical rotor iron core. The electric motor of the invention is a hexapole electric motor which has a rotor arranged by use of a neodymium rare earth magnet containing iron, neodymium, boron and dysprosium of 4 wt.% or less and 3 wt.% or more and which is driven according to weak magnetic field control.SELECTED DRAWING: Figure 23

Description

The present disclosure relates to an electric motor using a permanent magnet and a compressor equipped with the electric motor.

In order to improve the energy saving of the air conditioner, rare earth magnets (Nd-Fe-B (neodymium, iron, boron)) with high energy density are generally used as permanent magnets of electric motors installed in compressors. .. When a rare earth magnet (Nd-Fe-B) is used in a high temperature atmosphere such as a compressor, the coercive force of the magnet deteriorates due to the temperature rise. Therefore, it is necessary to design and drive such that the demagnetizing field generated by the stator is equal to or less than the demagnetizing field of the permanent magnet.

In order to increase the driving constraint due to demagnetization in a high temperature atmosphere, a method of adding a Dy (dysprosium) element to a rare earth magnet (Nd-Fe-B) to improve the coercive force is generally used. (For example, see Patent Document 1).

When the Dy element is added, the coercive force of the permanent magnet is improved, but on the contrary, the residual magnetic flux density is lowered. Further, since Dy is a valuable rare earth resource, its price is high and its usage amount is limited.

Japanese Patent No. 4241900 JP-A-2-130286 International Publication No. 2007/102391 JP, 2010-187521, A JP, 2010-158085, A JP 2000-152569 A JP 2001-268873 A JP, 2007-327497, A JP, 2001-123953, A International Publication No. 2010/100934 JP 2002-291209 A

"Development of High Performance Heat Resistant Nd-Fe-B System Sintered Magnet" Magnetics Jpn. Vol. 8, 2008, p. p. 372-376, The Magnificent Society of Japan

In order to make the structure of the electric motor strong against demagnetization without impairing the generation of torque, there is a method of increasing the thickness of the magnet or increasing the number of poles.

The method of increasing the thickness of the magnet is not preferable because it increases the magnet volume and the amount of rare earth Dy used.

In addition, in a design with an increased number of poles, the drive frequency increases in proportion to the number of poles, so iron loss generated in the core of the motor increases. Iron loss includes hysteresis loss and eddy current loss, both of which are expressed as a function of drive frequency.

Hysteresis loss is the loss when the magnetic domain of the iron core changes the direction of the magnetic field by the alternating magnetic field. It is expressed by the following Steinmetz empirical formula.
Ph=khfBm1.6 (1)
here,
Ph: Hysteresis loss kh: Proportional constant f: Frequency Bm: Maximum magnetic flux density

Eddy current loss is caused by the eddy current generated in the iron core. The ratio of eddy current loss increases as the frequency becomes higher.
Pe=ke(tfBm)2/ρ (2)
here,
Pe: eddy current loss ke: proportional constant t: thickness of iron plate f: frequency Bm: maximum magnetic flux density ρ: resistivity of magnetic material

In order to make it difficult for eddy currents to flow, a material with high magnetic permeability but low conductivity is used, and the size of the eddy currents is proportional to the square of the plate thickness. Measures such as stacking materials will be taken.

Further, in the design with the increased number of poles, the drive frequency increases in proportion to the number of poles. Therefore, when PWM drive is performed, if the switching carrier frequency is constant, the waveform generation of the sine wave current deteriorates, and Cannot drive efficiently. Therefore, when increasing the number of poles, the carrier frequency of the inverter is increased in proportion to the number of poles, but there is a problem that switching loss of the inverter increases and efficiency deteriorates.

The present disclosure provides a compressor that has a demagnetization resistance even when the amount of Dy (dysprosium) contained in a rare earth magnet used in an electric motor is reduced.

The electric motor according to the present disclosure is
A permanent magnet embedded type electric motor in which a flat plate-shaped permanent magnet is embedded along the outer peripheral edge of a cylindrical rotor core.
A neodymium rare earth magnet containing iron, neodymium, boron and dysprosium, which has a rotor using a neodymium rare earth magnet having a dysprosium content of 4% by weight or less and 3% by weight or more, and is driven by field weakening control. It is a 6-pole electric motor.

A compressor according to the present disclosure is a 6-pole electric motor having a compression element for compressing a refrigerant and a rotor for driving the compression element and using a neodymium rare earth magnet containing iron, neodymium, boron and 4 wt% or less of dysprosium. With the above, the residual magnetic flux density of the magnet is improved, and a compact and highly efficient compressor can be configured.

The figure shown for comparison and is a cross-sectional view of a general electric motor 100. FIG. 3 is a diagram for comparison and is a cross-sectional view of a stator 101 of a general electric motor 100. It is a figure shown for comparison and is a transverse cross-sectional view of a stator core 101a of a general electric motor 100. FIG. 3 is a view for comparison and is a cross-sectional view of a rotor 102 of a general electric motor 100. FIG. 3 is a view for comparison and is a cross-sectional view of a rotor core 102 a of a general electric motor 100. FIG. 3 is a diagram showing the relationship between the Dy content of a neodymium rare earth magnet and the coercive force/residual magnetic flux density. FIG. 3 is a diagram showing the relationship between the number of poles of the electric motor 100, the demagnetizing force of a permanent magnet, and the drive frequency of an inverter. 1 is a diagram showing the first embodiment and is a cross-sectional view of an electric motor 200. FIG. FIG. 3 shows the first embodiment and is a cross-sectional view of a stator 201. FIG. 3 is a diagram showing the first embodiment and is a cross-sectional view of a stator core 201a. FIG. 3 shows the first embodiment and is a cross-sectional view of a stator 201 using a PET film as an insulating material. 1 is a diagram showing the first embodiment and is a cross-sectional view of a stator 201 provided with measures against leakage current. FIG. 3 is a diagram showing the first embodiment and is a transverse cross-sectional view of a stator core 201a having a leakage current countermeasure. FIG. 3 shows the first embodiment and is a cross-sectional view of a rotor 202. FIG. 3 shows the first embodiment and is a cross-sectional view of a rotor core 202a. FIG. 3 is a diagram showing the first embodiment and is a transverse cross-sectional view of a rotor 202 obtained by dividing the permanent magnet 202b of each magnetic pole into two. FIG. 3 is a diagram showing the first embodiment and is a diagram showing the relationship between the demagnetization factor and the magnetomotive force when the number of poles is changed while keeping the thickness and Dy content of the permanent magnet constant. FIG. 3 is a diagram showing the first embodiment and is a cross-sectional view of a six-pole electric motor 200. FIG. 3 is a diagram showing the first embodiment and is a cross-sectional view of a 10-pole electric motor 200. FIG. 3 is a diagram showing the first embodiment and is a relational diagram between the Dy content and the number of poles required to secure a 1.5% demagnetization rate. FIG. 3 is a diagram showing the first embodiment and is a relationship diagram between motor efficiency and the number of poles. FIG. 3 shows the first embodiment and is a circuit diagram of a drive circuit 1 of an electric motor 200. FIG. 22 is a diagram showing the first embodiment, and is a comparison diagram of total efficiencies obtained by driving the electric motor in the case where the Dy content shown in the broken line of FIG. 1 is a diagram showing the first embodiment and is a vertical cross-sectional view of a rotary compressor 300 in which an electric motor 200 is mounted.

Embodiment 1.
FIG. 1 is a diagram shown for comparison and is a cross-sectional view of a general electric motor 100. The general electric motor 100 shown in FIG. 1 is, for example, a brushless DC motor. The electric motor 100 includes a stator 101 and a rotor 102 arranged inside the stator 101 with a gap 120.

The combination of the number of slots and the number of poles of the electric motor 100 is 6 slots and 4 poles. The electric motor 100 is driven at a variable speed by PWM control by the inverter of the drive circuit, thereby performing highly efficient operation according to the required product load condition. The switching carrier of the inverter has a waveform generated at 4.5 kHz, for example, and is driven at a variable speed by PWM control of the inverter or the like.

FIG. 2 is a view shown for comparison, and is a cross-sectional view of a stator 101 of a general electric motor 100. The stator 101 includes at least a stator core 101a and windings 101b (insulated from the stator core by an insulating material (not shown)). The winding 101b is a concentrated winding wound around the teeth 101a-1 (FIG. 3), but may be distributed winding. The winding 101b is a three-phase winding, and the connection method is Y connection (star connection, star connection). However, the connection method may be triangular connection.

FIG. 3 is a view shown for comparison, and is a cross-sectional view of a stator core 101a of a general electric motor 100. The stator core 101a is substantially ring-shaped (cylindrical), and has a ring-shaped core back 101a-2 formed on the outer peripheral side. Six teeth 101a-1 are radially formed on the rotor 102 side from the core back 101a-2. The six teeth 101a-1 are arranged at substantially equal intervals in the circumferential direction. The circumferential width of the tooth 101a-1 is substantially constant in the radial direction.

The space between the adjacent teeth 101a-1 is called a slot 101a-3. The number of slots 101a-3 is six, which is the same as the number of teeth 101a-1. Since the circumferential width of the tooth 101a-1 is substantially constant in the radial direction, the circumferential width of the slot 101a-3 gradually increases from the inner side toward the outer side (core back 101a-2 side). Is.

The stator core 101a is formed by laminating a predetermined number of thin electromagnetic steel plates having a thickness of 0.7 mm or less in a predetermined shape.

4 and 5 are views for comparison, FIG. 4 is a cross-sectional view of the rotor 102 of the general electric motor 100, and FIG. 5 is a cross-sectional view of the rotor core 102a of the general electric motor 100. .. The rotor 102 is a permanent magnet embedded type (embedded magnet type), and includes at least a rotor core 102a and a flat plate-shaped permanent magnet 102b inserted into the magnet insertion hole 102a-1 of the rotor core 102a.

The four permanent magnets 102b are inserted into magnet insertion holes 102a-1 formed along the outer peripheral edge of the rotor iron core 102a to form the four-pole rotor 102.

The permanent magnet 102b of the rotor 102 is composed of a neodymium rare earth magnet whose main component is Nd-Fe-B (neodymium/iron/boron) and has a flat plate shape with a thickness of about 2 mm.

The rotor core 102a has a substantially cylindrical shape, and four magnet insertion holes 102a-1 having a substantially rectangular cross section are formed along the outer peripheral edge. In the cross section, the four magnet insertion holes 102a-1 form a substantially quadrangular shape. A shaft hole 102a-2 into which a rotation shaft (not shown) is inserted is provided at a substantially central portion of the rotor core 102a.

Similarly to the stator core 101a, the rotor core 102a is also formed by forming a thin electromagnetic steel sheet having a thickness of 0.7 mm or less in a predetermined shape and stacking a predetermined number of sheets.

When a demagnetizing field is applied to the permanent magnet 102b, if the demagnetizing field is small, the magnetic characteristics are restored after the application (reversible demagnetization), but if the demagnetizing field exceeds a certain value, the magnetic characteristics deteriorate and the irreversible reduction does not occur. A phenomenon called magnetism occurs. A numerical value representing the degree of difficulty of irreversible demagnetization is called coercive force. When irreversible demagnetization occurs, the characteristics of the motor deteriorate. Therefore, select a load design and a holding force magnet that will not cause irreversible demagnetization by the demagnetizing field due to armature reaction.

The coercive force of a neodymium rare earth magnet containing Nd-Fe-B as a main component has a property of decreasing with temperature. When using an electric motor using a neodymium rare earth magnet in a high temperature atmosphere of 100° C. or higher such as a compressor, the coercive force of the magnet deteriorates with temperature (about −0.5 to −0.6%/ΔK). , Dy (dysprosium) elements must be added to improve the coercive force.

FIG. 6 is a relationship diagram between the Dy content of a neodymium rare earth magnet and the coercive force/residual magnetic flux density. As shown in FIG. 6, the coercive force of the neodymium rare earth magnet is improved almost in proportion to the Dy content.

In a general compressor, the upper limit of the ambient temperature of the electric motor is about 150°C. In a general compressor, an electric motor is used within a range of an upper limit (about 150° C.) in which a temperature rises by about 130° C. from a room temperature of 20° C. to a room temperature of 20° C. Therefore, for example, with a temperature coefficient of −0.5%/ΔK, the coercive force of the permanent magnet is reduced by 65%.

To prevent demagnetization under the maximum load of the compressor, a coercive force of about 1100 to 1500A/m is required, and the coercive force (about 1100 to 1500A/m) is guaranteed at an ambient temperature of 150°C. In order to do so, it is necessary to design the room temperature coercive force to be about 1800 to 2300 A/m.

In order to obtain the necessary coercive force (about 1100 to 1500 A/m), the room temperature coercive force of the neodymium rare earth magnet containing Nd-Fe-B as a main component is about 1000 A/m without adding the Dy element. Was added with 6 to 8% by weight of Dy element.

The production amount of Dy element in 2010 is concentrated in China, which causes price instability and procurement risk. Therefore, there is a demand to reduce the addition amount.

Further, as shown in FIG. 6, when the Dy element is added, there is a demerit that the coercive force characteristic is improved but the residual magnetic flux density characteristic is lowered. When the residual magnetic flux density is reduced, the magnet torque of the electric motor is reduced and the energizing current is increased, so that the copper loss is increased. Therefore, there is a great demand for reducing the amount of Dy added in terms of efficiency.

FIG. 7 is a relationship diagram between the number of poles of the electric motor 100, the demagnetizing force applied to the permanent magnets, and the drive frequency of the inverter. The demagnetizing force applied to the permanent magnet is proportional to the winding magnetomotive force, and is inversely proportional to the magnet thickness and the number of poles. In order to construct an electric motor that is resistant to demagnetization without impairing the generation of torque, it is preferable to design the magnet thickness to be thick or the number of poles to be large.

When the thickness of the magnet is increased, the magnet volume itself is increased, and the amount of Dy used is increased, which is not preferable.

In a design with an increased number of poles, the drive frequency increases in proportion to the number of poles. Therefore, there is a problem that the iron loss generated in the core of the electric motor and the switching loss of the inverter increase, and the efficiency deteriorates.

The electric motor of the present embodiment is configured with a number of poles of 6 poles or more, suppresses the Dy content contained in the rare earth magnet to 4% by weight or less, and uses a device using SiC for the switching portion of the inverter main circuit. By driving with a drive circuit, the said subject is solved.

FIG. 8 shows the first embodiment and is a cross-sectional view of the electric motor 200. The electric motor 200 shown in FIG. 8 is, for example, a brushless DC motor. The electric motor 200 includes a stator 201 and a rotor 202 arranged inside the stator 201 with a gap 220.

The combination of the number of slots and the number of poles of the electric motor 200 is 12 slots and 8 poles.

FIG. 9 is a view showing the first embodiment and is a cross-sectional view of the stator 201. The stator 201 includes at least a stator core 201a, a winding 201b, and an insulating material 201c that insulates the stator core 201a and the winding 201b from each other.

The winding 201b is a concentrated winding wound around the tooth 201a-1 (FIG. 10), but may be distributed winding. The winding 201b is a three-phase winding, and the connection method is Y connection (star connection, star connection). However, the connection method may be triangular connection.

FIG. 10 is a view showing the first embodiment and is a cross-sectional view of the stator core 201a. The stator core 201a is substantially ring-shaped (cylindrical), and a ring-shaped core back 201a-2 is formed on the outer peripheral side. Twelve teeth 201a-1 are radially formed from the core back 201a-2 to the rotor 202 side. The 12 teeth 201a-1 are arranged at substantially equal intervals in the circumferential direction. The circumferential width of the teeth 201a-1 is substantially constant in the radial direction.

The space between the adjacent teeth 201a-1 is called a slot 201a-3. The number of slots 201a-3 is twelve, which is the same as the number of teeth 201a-1. Since the circumferential width of the tooth 201a-1 is substantially constant in the radial direction, the circumferential width of the slot 201a-3 gradually increases from the inner side toward the outer side (core back 201a-2 side). Is.

The stator core 201a is formed by forming thin electromagnetic steel sheets having a thickness of 0.7 mm or less in a predetermined shape and stacking a predetermined number of sheets.

In the case of 12 slots, the winding work is doubled as compared with 6 slots. When the total of the slot openings 201a-4 of the stator 201 is the same, the width of the slot openings 201a-4 is smaller than that of 6 slots. When the stator core 201a is made of one piece, the work of inserting the winding 201b becomes very difficult.

In the stator core 201a of the present embodiment, the core is divided for each tooth 201a-1 to perform winding, and the divided core is fixed in an annular shape after the winding. When the multi-pole structure is used, the number of slots also increases. Therefore, the space factor of the winding is higher and the productivity is better when the split core method is used.

An insulating material 201c for insulating the winding 201b and the stator core 201a is interposed in the slot 201a-3. The insulating material 201c is generally formed by molding a resin, and has a thickness of about 1 mm in order to secure molding strength. When the number of slots is increased in the multi-pole configuration, the amount of the insulating material 201c is increased, so that the winding area is reduced and the copper loss is increased, which is not preferable.

FIG. 11 is a diagram showing the first embodiment and is a cross-sectional view of a stator 201 using a PET film as an insulating material. By using the PET film 201c-1 for insulation in the slot 201a-3 as shown in FIG. 11, it is possible to suppress an increase in the insulating material due to an increase in the number of slots, and to provide a highly efficient electric motor even in the case of a multipolar multislot configuration. Can be configured.

12 and 13 are views showing the first embodiment, FIG. 12 is a cross-sectional view of a stator 201 having leakage current countermeasures, and FIG. 13 is a cross-sectional view of a stator core 201a having leakage current countermeasures. is there.

When the number of poles is increased and the inverter carrier frequency is increased, leakage current easily flows due to stray capacitance between the winding and the core (stator core).

Therefore, as shown in FIG. 13, the core back 201a-2 portion of the slot 201a-3 is hollowed out to form a cutout portion 201a-5. The cutout portions 201a-5 are formed on both sides of each tooth 201a-1.

With this configuration, it is possible to reduce the electrostatic capacitance between the winding 201b and the stator core 201a and reduce the leakage current.

14 and 15 are views showing the first embodiment, FIG. 14 is a cross-sectional view of the rotor 202, and FIG. 15 is a cross-sectional view of the rotor core 202a.

The rotor 202 is a permanent magnet embedded type, and includes at least a rotor core 202a and a flat permanent magnet 202b that is inserted into the magnet insertion hole 202a-1 of the rotor core 202a.

The eight permanent magnets 202b are formed into magnet insertion holes 202a-1 formed along the outer peripheral edge of the rotor core 202a, and form the eight-pole rotor 202.

The permanent magnet 202b is mounted with a neodymium rare earth magnet containing Nd-Fe-B (neodymium, iron, boron) as a main component, and has a flat plate shape with a thickness of about 2 mm. In the present embodiment, the Dy content is 3% by weight.

In other words, the permanent magnet 202b is a neodymium rare earth magnet containing Fe (iron), Nd (neodymium), Dy (dysprosium), and B (boron). In addition, it contains trace impurities.

The rotor core 202a has a substantially cylindrical shape, and eight magnet insertion holes 202a-1 having a substantially rectangular cross-sectional shape are formed along the outer peripheral edge. In the cross section, the eight magnet insertion holes 202a-1 form a substantially octagonal shape. A shaft hole 202a-2 into which a rotary shaft (not shown) is inserted is provided at a substantially central portion of the rotor core 202a.

The rotor core 202a is formed by laminating a predetermined number of thin electromagnetic steel plates having a thickness of 0.7 mm or less in a predetermined shape.

FIG. 16 is a view showing the first embodiment, and is a cross-sectional view of the rotor 202 obtained by dividing the permanent magnet 202b of each magnetic pole into two parts. When the electric motor has multiple poles, the driving frequency increases, so that the loss due to the eddy current flowing through the permanent magnet 202b increases. In FIG. 16, the permanent magnet 202b of each magnetic pole is divided into two in the width direction (circumferential direction). As a result, by increasing the specific resistance of the permanent magnet 202b, it becomes difficult for eddy current to flow, and heat generation of the permanent magnet 202b due to loss (eddy current loss) is suppressed.

FIG. 17 shows the first embodiment, and is a relationship diagram between the demagnetization rate and the magnetomotive force when the thickness and Dy content of the permanent magnet are fixed and the number of poles is changed. In FIG. 17, the demagnetization rate is expressed by the reduction rate based on the ratio of the induced voltage before and after energization, with the stator and rotor fixed to energize so that a magnetic flux having a phase opposite to that of the permanent magnet is generated. ing. The horizontal axis is the index of the magnetomotive force, which is the product of the applied current and the number of turns of the phase. In the compressor, the product performance guarantee value is designed so that the demagnetization rate is within 1.5%, for example.

18 and 19 are views showing the first embodiment, FIG. 18 is a cross-sectional view of a 6-pole electric motor 200, and FIG. 19 is a cross-sectional view of a 10-pole electric motor 200.

The 6-pole electric motor 200 shown in FIG. 18 is a 9-slot 6-pole electric motor in which the stator 201 has nine slots 201a-3 and the rotor 202 has six permanent magnets 202b.

The 10-pole electric motor 200 shown in FIG. 19 is a 12-slot 10-pole electric motor in which the stator 201 has 12 slots 201a-3 and the rotor 202 has 6 permanent magnets 202b.

From FIG. 17, it can be seen that as the number of poles increases, the magnetomotive force for demagnetizing by 1.5% increases. When using 4 poles as a reference, the magnetomotive force for demagnetizing 1.5% is about 1.5 times for 6 poles, about 2 times for 8 poles and about 2.5 times for 10 poles. Has improved. When the atmospheric temperature of the electric motor and the generated load torque are constant, the larger the number of poles, the lower the coercive force, that is, the magnet having the smaller Dy content can be used. This is because demagnetizing force is reduced because the demagnetizing field generated by the stator is dispersed by using multiple poles.

FIG. 20 is a diagram showing the first embodiment, and is a relationship diagram between the Dy content and the number of poles required to secure the 1.5% demagnetization rate. From FIG. 20, by increasing the number of poles, it is possible to design with a reduced Dy content in terms of demagnetization proof strength. In the case of 6 poles, a permanent magnet having a Dy content suppressed to 4% by weight or less can be used. Similarly, in the case of 8 poles, the maximum Dy content is 3 wt% or less, and in the case of 10 poles, the permanent magnet whose Dy content is suppressed to the maximum 2 wt% or less can be used.

When the number of poles of the electric motor is increased, the magnetic flux density generated in the core of the electric motor is reduced, but the frequency of the magnetic flux density is increased. Therefore, increasing the number of poles too much increases iron loss.

FIG. 21 shows the first embodiment, and is a relationship diagram between the motor efficiency and the number of poles. When the number of poles of the motor is increased, the number of slots in the stator increases, so the area of the insulating material that insulates the windings of the stator from the slots increases, reducing the cross-sectional area of the windings and reducing copper loss. Will increase. Therefore, in the case of designing with the same permanent magnet (constant Dy content) as in the conventional case, as shown by the solid line in FIG. 21, the motor efficiency in the case of four poles was the best.

However, as described above, in order to improve the demagnetization resistance, the Dy content in the case of 6 poles is up to 4% or less, the Dy content in the case of 8 poles is up to 3% by weight or less, and the Dy content in case of 10 poles is up to 2%. When it is reduced to not more than wt%, the residual magnetic flux density of the permanent magnet is improved. Therefore, the size of the electric motor can be reduced, and iron loss and copper loss can be reduced.

As indicated by the broken line in FIG. 21 showing the motor efficiency when the Dy content is reduced, it can be seen that when the Dy content is reduced, the motor efficiency can be designed without lowering the efficiency even if it is 6 poles or more.

The motor efficiency is preferably 6 poles with a Dy content reduced to 4 wt% or less, 8 poles with a Dy content reduced to a maximum of 3 wt% or less, and 10 poles with a Dy content reduced to a maximum of 2 wt% or less. Is. When the number of poles is 12 or more, the increase in iron loss due to an increase in driving frequency is more important than the improvement in residual magnetic flux density, so the motor efficiency is lower than that of 6 to 10 poles. The motor of the compressor is designed to have a rated rotation speed of 60 rps and a maximum rotation speed of about 120 rps.

The electric motor of the present embodiment is driven at a variable speed by PWM control by the inverter of the drive circuit, thereby performing highly efficient operation in accordance with the required product load condition. The switching carrier of the inverter has a waveform generated at, for example, 9 kHz, and is driven at a variable speed by PWM control of the inverter or the like.

Next, the drive circuit 1 of the electric motor 200 will be described. FIG. 22 shows the first embodiment, and is a circuit diagram of the drive circuit 1 of the electric motor 200. AC power is supplied to the drive circuit 1 from a commercial AC power supply 2 provided outside. The AC voltage supplied from the commercial AC power supply 2 is converted into a DC voltage by the rectifier circuit 3. The DC voltage converted by the rectifier circuit 3 is converted into an AC voltage having a variable frequency by the inverter main circuit 4 and applied to the electric motor 200. The electric motor 200 is driven by AC power of variable frequency supplied from the inverter main circuit 4. The rectifier circuit 3 includes a chopper circuit that boosts the voltage applied from the commercial AC power supply 2, a smoothing capacitor that smoothes the rectified DC voltage, and the like.

The inverter main circuit 4 is a three-phase bridge inverter circuit, and the switching part of the inverter main circuit 4 is composed of six IGBTs 6a to 6f (insulated gate bipolar transistors) serving as inverter main elements and six flywheel diodes (FRD) as silicon carbide. SiC-SBDs 7a to 7f (Schottky barrier diodes) using (SiC) are provided. The FRDs, SiC-SBDs 7a to 7f, are reverse current preventing means for suppressing the counter electromotive force generated when the IGBTs 6a to 6f turn the current from ON to OFF.

Note that, here, the IGBTs 6a to 6f and the SiC-SBDs 7a to 7f are IC modules in which each chip is mounted on the same lead frame and molded by an epoxy resin and packaged. Each of the IGBTs 6a to 6f may be an IGBT using SiC or GaN (gallium nitride) instead of the IGBT (Si-IGBT) using silicon, or a MOSFET (Metal-Oxide) using Si or SiC or GaN instead of the IGBT. Other switching elements such as -Semiconductor Field-Effect Transistor may be used.

Two voltage dividing resistors 8a and 8b connected in series are provided between the rectifier circuit 3 and the inverter main circuit 4, and a high voltage DC voltage is reduced by a voltage dividing circuit by the voltage dividing resistors 8a and 8b. A DC voltage detector 8 for sampling and holding the electric signal is provided.

Current detection elements 30a and 30c that detect a current flowing through the U-phase winding 201b-u and the W-phase winding 201b-w of the electric motor 200 are provided. A direct current transformer (DCCT), an alternating current transformer (ACCT), or the like is used as the current detection elements 30a and 30c, and detects the instantaneous value of the current flowing through the U-phase winding 201b-u and the W-phase winding 201b-w.

The rotor position detection unit 10 calculates the position of the rotor 202 of the electric motor 200 from the output signals of the current detection elements 30a and 30c, and outputs the position information of the rotor 202 to the output voltage calculation unit 9. Here, although the currents of the two phases of the U-phase winding 201b-u and the W-phase winding 201b-w of the electric motor 200 are detected, the currents of the V-phase winding 201b-v and the three-phase are added. The current may be detected, or the current for two phases of another combination may be detected.

The rotor position detection unit 10 may detect the terminal voltage of the electric motor 200 to detect the position of the rotor 202 of the electric motor 200.

The position information of the rotor 202 detected by the rotor position detector 10 is output to the output voltage calculator 9. The output voltage calculation unit 9 is an optimum inverter main unit to be added to the electric motor 200 based on the command of the target rotation speed N given from the outside of the drive circuit 1 or the information on the operating conditions of the device and the position information of the rotor 202. The output voltage of the circuit 4 is calculated. The output voltage calculator 9 outputs the calculated output voltage to the PWM signal generator 31. PWM is an abbreviation for Pulse Width Modulation.

The PWM signal generation unit 31 outputs a PWM signal having an output voltage given from the output voltage calculation unit 9 to the main element drive circuit 4a that drives each of the IGBTs 6a to 6f of the inverter main circuit 4, and the inverter main circuit 4a. The four IGBTs 6a to 6f are switched by the main element drive circuit 4a.

Here, a control method for suppressing the demagnetizing field of the stator 201 will be described. The demagnetizing field of the stator 201 is generated by mistake when a large current flows through the winding 201b (U-phase winding 201b-u, V-phase winding 201b-v, and W-phase winding 201b-w).

In the present embodiment, the instantaneous value of the current flowing in the winding 201b is detected, and when the detected instantaneous current value becomes higher than the predetermined current value, the output voltage calculation unit 9 outputs the output to the PWM signal generation unit 31. Since a large current does not flow through the winding 201b, the demagnetization of the permanent magnet 202b due to the demagnetizing field of the stator 201 can be suppressed, and the motor 200 having high reliability can be provided. Obtainable.

Here, the wide band gap semiconductor will be described. The wide bandgap semiconductor is a general term for semiconductors having a bandgap larger than Si, and SiC used in the SiC-SBDs 7a to 7f is one of the wide bandgap semiconductors, and gallium nitride (GaN), There are diamonds. Furthermore, wide band gap semiconductors, especially SiC, have higher heat resistance temperature, dielectric breakdown strength, and thermal conductivity than Si. Although SiC is used for the FRD of the inverter circuit here, other wide band gap semiconductors may be used instead of SiC.

SiC has excellent physical properties such as a dielectric breakdown voltage 10 times that of Si and a bandgap 3 times that of Si. The breakdown voltage of the power device is supported by the epitaxial layer (drift layer), but it also becomes a resistance when it is turned on. Since the breakdown voltage of SiC is 10 times that of Si, the thickness of the epitaxial layer can be reduced to 1/10 and the on-resistance can be reduced. Further, since the band gap is wide, high temperature operation of 200° C. or higher is possible. Further, Si performs hole injection to reduce the on-resistance, recovery is slow, and SiC that does not require recovery has fast recovery, which can significantly reduce recovery loss and enables high-speed switching with low loss.

FIG. 23 is a diagram showing the first embodiment and is a comparison diagram of the total efficiency when the inverter element drives the electric motor when the Dy content shown in the broken line of FIG. 21 is reduced when the inverter element is Si and SiC. As described above, as the number of poles increases, the driving frequency also increases, so that it is necessary to increase the carrier frequency of the inverter, which increases switching loss of the inverter. Therefore, when the Si element shown by the solid line is used, the total efficiency of the four poles is the highest.

On the other hand, when the SiC element indicated by the broken line is used, the switching loss can be significantly reduced, so that a highly efficient drive system can be configured even when the number of poles is 6 or more.

The electric motor 200 of the present embodiment performs field weakening control in a region where the induced voltage at high speed exceeds the terminal voltage. By controlling the advance of the current that causes the stator magnetic field to be generated in the winding 201b of the stator 201 in the direction opposite to that of the permanent magnet 202b, the induced voltage generated by the permanent magnet 202b is suppressed and the torque is increased.

Since the field weakening control generates a stator magnetic field in a direction facing the permanent magnet 202b, it greatly affects the demagnetization resistance. If the weakening amount of the field weakening control is small, the permanent magnet 202b having a small coercive force (small Dy content) can be used more easily.

In order not to perform the field weakening control, the design may be such that the induced voltage is lowered or the terminal voltage output by the converter is designed by boosting a commercial 200V power supply. Designing with a lower induced voltage reduces the number of turns of the winding or reduces the magnetic force of the permanent magnet, which increases the motor current, increases the conduction loss of the inverter, and increases the copper loss. ..

When the voltage is boosted by the converter, there is a problem of withstand voltage of the element, but by using a SiC element having a high withstand voltage, it is possible to significantly boost the voltage as compared with the conventional case. Therefore, in the circuit using the SiC element in the converter, the Dy content of the permanent magnet is made smaller than that in the conventional control by boosting the voltage to 80 to 100% of the voltage at which the electric motor saturates and driving the weakening magnetic field to a smaller magnitude. Further reduction is possible.

FIG. 24 is a view showing the first embodiment and is a vertical sectional view of a rotary compressor 300 in which the electric motor 200 is mounted. An example of the rotary compressor 300 (compressor) shown in FIG. 24 is a vertical type in which the sealed container 70 has a high pressure. The compression element 400 is housed in the lower part of the closed container 70. An electric motor 200, which is an electric element for driving the compression element 400, is housed above the compression element 400 in the upper part of the closed container 70.

Refrigerating machine oil 90 that lubricates the sliding parts of the compression element 400 is stored at the bottom of the closed container 70.

First, the configuration of the compression element 400 will be described. The cylinder 401, in which the compression chamber is formed, has a cylinder chamber (not shown) having a substantially circular outer surface in a plan view and a substantially circular space in a plan view inside. The cylinder chamber is open at both ends in the axial direction. The cylinder 401 has a predetermined axial height in a side view.

A parallel vane groove (not shown) extending in the radial direction is provided so as to communicate with a cylinder chamber, which is a substantially circular space of the cylinder 401, and penetrate in the axial direction.

Further, on the back surface (outside) of the vane groove, there is provided a back surface chamber (not shown) which is a space having a substantially circular shape in plan view and which communicates with the vane groove.

A suction port (not shown) through which suction gas from the refrigeration cycle passes through the cylinder 401 extends from the outer peripheral surface of the cylinder 401 into the cylinder chamber.

The cylinder 401 is provided with a discharge port (not shown) that is cut out near the edge of the circle (the end surface on the electric motor 200 side) that forms the cylinder chamber that is a substantially circular space.

The material of the cylinder 401 is gray cast iron, sintered, carbon steel or the like.

The rolling piston 402 eccentrically rotates in the cylinder chamber. The rolling piston 402 has a ring shape, and the inner circumference of the rolling piston 402 is slidably fitted to the eccentric shaft portion 50 a of the rotary shaft 50.

The outer circumference of the rolling piston 402 and the inner wall of the cylinder chamber of the cylinder 401 are assembled so that there is always a constant gap.

The material of the rolling piston 402 is alloy steel containing chromium or the like.

The vane 403 is housed in the vane groove of the cylinder 401, and the vane 403 is constantly pressed against the rolling piston 402 by the vane spring 408 provided in the back pressure chamber. Since the rotary compressor 300 has a high pressure inside the hermetic container 70, when the operation is started, a force due to the differential pressure between the high pressure inside the hermetic container 70 and the pressure inside the cylinder chamber acts on the back surface (the back pressure chamber side) of the vane 403. Therefore, the vane spring 408 is mainly used for the purpose of pressing the vane 403 against the rolling piston 402 when the rotary compressor 300 is started up (when there is no difference in pressure between the closed container 70 and the cylinder chamber).

The vane 403 has a flat, substantially rectangular shape (the thickness in the circumferential direction is smaller than the length in the radial direction and the axial direction).

High speed tool steel is mainly used as the material of the vane 403.

The main bearing 404 is slidably fitted to the main shaft portion 50b of the rotary shaft 50 (a portion above the eccentric shaft portion 50a and fitted to the rotor 20), and at the same time, to the cylinder chamber (vane groove) of the cylinder 401. One end surface (on the side of the electric motor 200) is closed.

The main bearing 404 includes a discharge valve (not shown). However, it may be attached to either or both of the main bearing 404 and the sub bearing 405.

The main bearing 404 has a substantially inverted T shape when viewed from the side.

The sub bearing 405 slidably fits to the sub shaft portion 50c of the rotary shaft 50 (a portion below the eccentric shaft portion 50a), and at the same time, the other end surface of the cylinder chamber (including the vane groove) of the cylinder 401 (refrigeration) The machine oil 90 side) is closed.

The sub bearing 405 has a substantially T-shape in side view.

The material of the main bearing 404 and the auxiliary bearing 405 is the same as that of the cylinder 401, and is gray cast iron, sintered, carbon steel or the like.

A discharge muffler 407 is attached to the outer side (the electric motor 200 side) of the main bearing 404. The high-temperature, high-pressure discharge gas discharged from the discharge valve of the main bearing 404 enters the discharge muffler 407 at one end and is then discharged from the discharge muffler 407 into the closed container 70. However, in some cases, the discharge muffler 407 may be provided on the side of the auxiliary bearing 405.

A suction muffler 51 that sucks low-pressure refrigerant gas from the refrigeration cycle and suppresses direct suction of the liquid refrigerant into the cylinder chamber of the cylinder 401 when the liquid refrigerant returns is provided beside the hermetic container 70. The suction muffler 51 is connected to the suction port of the cylinder 401 via a suction pipe 52. The main body of the suction muffler 51 is fixed to the side surface of the closed container 70 by welding or the like.

A terminal 74 (referred to as a glass terminal) that is connected to a power source that is a power supply source is fixed to the sealed container 70 by welding. In the example of FIG. 24, the terminal 74 is provided on the upper surface of the closed container 70. A lead wire 73 from the electric motor 200, which is an electric element, is connected to the terminal 74.

A discharge pipe 75 having both ends opened is fitted on the upper surface of the hermetic container 70. The discharge gas discharged from the compression element 400 is discharged from the inside of the closed container 70 through the discharge pipe 75 to the external refrigeration cycle.

A general operation of the rotary compressor 300 will be described. Electric power is supplied from the terminal 74 and the lead wire 73 to the stator 201 of the electric motor 200, which is an electric element, so that the rotor 202 rotates. Then, the rotary shaft 50 fixed to the rotor 202 rotates, and the rolling piston 402 eccentrically rotates in the cylinder chamber of the cylinder 401 accordingly. A space between the cylinder chamber of the cylinder 401 and the rolling piston 402 is divided into two by a vane 403. With the rotation of the rotary shaft 50, the volumes of these two spaces are changed, and the volume is gradually expanded on one side to suck the refrigerant from the suction muffler 51, and the volume is gradually reduced on the other side. The refrigerant gas is compressed. The compressed discharge gas is once discharged from the discharge muffler 407 into the closed container 70, further passes through the electric motor 200 as an electric element, and is discharged from the discharge pipe 75 on the upper surface of the closed container 70 to the outside of the closed container 70. ..

The discharge gas passing through the electric motor 200, which is an electric element, is, for example, a void 220 (see FIG. 8) including a wind hole portion (through hole) of the rotor 202 of the electric motor 200 (not shown) and a slot opening portion (not shown) of the stator 201. ), and passes through a notch (see FIG. 9) arranged on the outer periphery of the stator 201. The refrigerant is R410A, R407C or the like.

1 drive circuit, 2 commercial AC power supply, 3 rectifier circuit, 3a reactor, 3b rectifying diode, 3c smoothing capacitor, 4 inverter main circuit, 4a main element drive circuit, 6a to 6f IGBT, 7a to 7f SiC-SBD, 8 DC voltage Detecting unit, 8a voltage dividing resistor, 8b voltage dividing resistor, 9 output voltage calculating unit, 10 rotor position detecting unit, 30a current detecting element, 30c current detecting element, 31 PWM signal generating unit, 50 rotating shaft, 50a eccentric shaft unit , 50c secondary shaft part, 51 suction muffler, 70 closed container, 73 lead wire, 74 terminal, 75 discharge pipe, 90 refrigeration oil, 100 electric motor, 101 stator, 101a stator core, 101b winding, 101a-1 teeth, 101a-2 core back, 101a-3 slot, 102 rotor, 102a rotor core, 102a-1 magnet insertion hole, 102a-2 shaft hole, 102b permanent magnet, 120 air gap, 200 electric motor, 201 stator, 201a stator Iron core, 201a-1 teeth, 201a-2 core back, 201a-3 slot, 201a-4 slot opening, 201a-5 notch, 201b winding, 201b-u U-phase winding, 201b-v V-phase winding , 201b-w W-phase winding, 201c insulating material, 201c-1 PET film, 202 rotor, 202a rotor core, 202a-1 magnet insertion hole, 202a-2 shaft hole, 202b permanent magnet, 220 air gap, 300 rotary Compressor, 400 compression element, 401 cylinder, 402 rolling piston, 403 vane, 404 main bearing, 405 auxiliary bearing, 407 discharge muffler, 408 vane spring.

Claims (6)

A permanent magnet embedded type electric motor in which a flat plate-shaped permanent magnet is embedded along the outer peripheral edge of a cylindrical rotor core.
A neodymium rare earth magnet containing iron, neodymium, boron and dysprosium, which has a rotor using a neodymium rare earth magnet having a dysprosium content of 4% by weight or less and 3% by weight or more, and is driven by field weakening control. 6-pole electric motor. A permanent magnet embedded type electric motor in which a flat plate-shaped permanent magnet is embedded along the outer peripheral edge of a cylindrical rotor core.
A neodymium rare earth magnet containing iron, neodymium, boron and dysprosium, which has a rotor using a neodymium rare earth magnet having a dysprosium content of 3% by weight or less and 2% by weight or more, and is driven by field weakening control. 8-pole electric motor. A permanent magnet embedded type electric motor in which a flat plate-shaped permanent magnet is embedded along the outer peripheral edge of a cylindrical rotor core.
A neodymium rare earth magnet containing iron, neodymium, boron and dysprosium, which has a rotor using a neodymium rare earth magnet having a dysprosium content of 2% by weight or less and 1.6% by weight or more, and has a weak field control. An electric motor with 10 poles to drive. The electric motor according to any one of claims 1 to 3, wherein the stator core of the electric motor is composed of split cores. The electric motor according to any one of claims 1 to 3, wherein the winding insulation of the stator of the electric motor is made of a PET film. A compressor provided with the electric motor according to any one of claims 1 to 5.

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