JP5393605B2 - Electric motor stator - Google Patents

Description

  The present invention relates to an insulating structure in a slot of a stator of an electric motor driven by an inverter.

  In general, in an electric motor, even if the winding in the slot and the stator core are insulated by an insulating material, there is a floating capacitance between the winding and the stator core, and insulation against high frequency is present. It may become smaller and leakage current may occur. When driving a motor with a commercial power supply (50/60 Hz), there is little problem, but when high-frequency operation of a motor by PWM control such as an inverter is performed, the floating capacitance between the winding and the stator core The resulting leakage current becomes a problem.

  In a mold stator in which the stator is molded with resin, since the mold stator is covered with resin, leakage current is less likely to be a problem. For example, in a hermetic compressor, since the stator is directly fixed to a steel plate sealed container, the values specified in the Electrical Appliance and Material Control Law (the charging unit and the surface of the container and the It is necessary to take measures to keep the leakage current flowing between 1 mA and 1).

  Conventionally, in an electric motor having a stator in which a conductor such as a copper wire is wound through an insulating paper in a slot of a stator core in which a stator core sheet made of electromagnetic steel sheets is laminated, the characteristics of the electric motor can be reduced. For the purpose of providing a stator that can reduce the leakage current of an electric motor without affecting the assemblability and cost, the shape in the slot of the stator core sheet is made into a plurality of concave and convex shapes. A laminated stator core of an electric motor has been proposed (see, for example, Patent Document 1).

JP-A-8-107642

  However, since the thing of the said patent document 1 has provided the unevenness | corrugation in the slot inner periphery, although the floating electrostatic capacitance between a stator iron core and a coil | winding can be reduced certainly, the magnetic path of teeth | gear is carried out by unevenness | corrugation. It becomes narrower. Therefore, there is a problem that the magnetic flux density of the teeth increases and the iron loss increases.

  Further, in the case of concentrated winding, since winding is performed while pressing the winding against the side surface of the teeth, the unevenness deteriorates the alignment of the winding, the winding space factor deteriorates, and copper loss increases. Furthermore, in the case of concentrated winding, when the winding is arranged so as to fit in the unevenness, the distance between the winding and the stator core does not increase, so the effect of reducing stray capacitance is reduced and leakage current is reduced. It can be said that the effect is small.

  Insulator insulation, which is a resin molded product, is generally used for insulation between the winding and the stator core, but in order to improve the characteristics of the motor, film insulation (PET) is used instead of insulator insulation. A film (a thin insulating material such as a PET film is a polymer film having a formal name of “polyethylene terephthalate”) may be used. By using film insulation instead of insulator insulation, the available slot area can be increased, and for example, the coil amount can be increased by about 30%. Accordingly, copper loss is reduced, and motor efficiency can be greatly improved.

  In this case, since the film insulation is thinner than the insulator insulation, the leakage current due to the stray capacitance between the winding and the stator core increases. Further, when the motor is operated at a high frequency by PWM control such as an inverter, the leakage current further increases.

  The present invention has been made to solve the above-described problems, and uses a thin film insulation such as a PET film to enlarge the winding cross-sectional area, thereby constituting a highly efficient motor with reduced copper loss. In some cases, a stator for an electric motor is provided that can reduce leakage current without reducing efficiency and winding performance even when thin film insulation is used.

The stator of the electric motor according to the present invention is a stator of an electric motor driven at a variable speed by PWM control such as an inverter.
The stator of the motor
A stator core composed of a plurality of divided teeth, and a slot is formed between the divided teeth;
Winding wound around the teeth of the split teeth in a concentrated winding method;
Film insulation that insulates between the winding and the slot inner circumference;
And a groove having a predetermined shape formed on the bottom side of the slot.

  In the motor stator of the present invention, a groove is provided at the bottom of the slot, so that the distance between the winding and the stator core at the bottom of the slot can be widened. And leakage current can be reduced.

It is a figure which shows the comparative example 1, and is a cross-sectional view of the electric motor 200. The figure which shows the part for 1 teeth of the stator 210 of FIG. The figure which shows the part for 1 teeth of the stator 210 of FIG. 1 ((a) is a cross-sectional view, (b) is AA sectional drawing of (a)). FIG. 9 is a diagram showing a comparative example 2 and a cross-sectional view of the electric motor 300. The figure which shows the part for 1 teeth of the stator 310 of FIG. The figure which shows the part for one teeth of the stator 310 of FIG. 4 ((a) is a cross-sectional view, (b) is a BB cross-sectional view of (a)). It is a figure which shows the comparative example 2, Comprising: The perspective view which shows the tea score 311a which gave the edge part insulator 313-1. It is a figure which shows the comparative example 2, and is a perspective view which shows the tea score 311a which gave the edge part insulator 313-1 which changed the angle seen with FIG. The characteristics of the stator 210 of Comparative Example 1 (insulation on the side surface of the tea score 211a was constituted by the insulator 213) and the stator 310 of Comparative Example 2 (insulation on the side surface of the tea score 311a were constituted by the film insulation 313) were compared. Figure. FIG. 3 shows the first embodiment and is a cross-sectional view of the electric motor 100. FIG. 5 shows the first embodiment and is a cross-sectional view of the stator 110. The figure which shows the part for 1 teeth of FIG. FIG. 5 shows the first embodiment, and is a transverse cross-sectional view of the stator core 111. FIG. 5 shows the first embodiment, and is a perspective view of a stator core 111. Fig. 5 shows the first embodiment, and is a plan view of a tea score 111a. Fig. 5 shows the first embodiment, and is a plan view of a stator core 111 developed in a band shape. FIG. 5 shows the first embodiment, and is a plan view showing a state in which winding is performed by reversely bending the stator core 111 so that the teeth 116 are on the outside. FIG. 3 shows the first embodiment, and is a circuit diagram of a drive circuit 1 of the electric motor 100. FIG. 5 shows the first embodiment, and shows measurement results of stray capacitance between the stator core and the windings of the conventional and the present embodiment. Fig. 5 shows the first embodiment, and is a plan view of a tea score 111a. FIG. 9 shows the first embodiment and is a plan view of a tea score 111a-1 of a first modification. The figure which shows the magnetic flux line analysis result of the electric motor without a groove | channel in the conventional slot. The figure which shows the magnetic flux line analysis result of the electric motor which provided the groove | channel in the slot of this Embodiment. The figure which compared the characteristic of the electric motor which provided the groove | channel in the slot of the conventional slot and the electric motor which does not have a slot in this Embodiment. FIG. 9 shows the first embodiment and is a plan view of a tea score 111a-2 of a second modification. The figure which shows Embodiment 1 and the figure which shows the state which gave the coil | winding 112 to the tee score 111a-2 of the modification 2. FIG. FIG. 9 shows the first embodiment and is a plan view of a tea score 111a-3 of Modification 3. FIG. 5 shows the first embodiment, and shows a state in which a winding 112 is applied to a tee score 111a-3 of a third modification. FIG. 10 shows the first embodiment and is a perspective view of a stator core 411 of a fourth modification. FIG. 10 is a diagram showing the first embodiment, and is a perspective view of a tea score 411a that is a divided tooth that constitutes the stator core 411 of Modification 4. The figure which shows Embodiment 1, The top view of the 1st tea score board 411a-1 and the 2nd tea score board 411a-2 which comprise the tea score 411a ((a) is the 1st tea score board 411a- 1 and (b) are second tea score plates 411a-2). FIG. 5 shows the first embodiment and shows a current waveform at the time of inverter driving.

Embodiment 1 FIG.
The loss of the motor is mainly composed of copper loss and iron loss, and it is necessary to reduce both in order to increase the efficiency of the motor mounted on the energy-saving equipment such as an air conditioner. The copper loss Wc is expressed as Wc = RI ² where I is the energizing current and R is the winding resistance. In order to reduce the copper loss Wc, it is required to reduce the energization current I or the winding resistance R. Since the current is a value that is arbitrarily determined when the load condition is determined, a configuration that reduces the winding resistance is necessary to reduce the copper loss of the motor.

  The winding resistance R is expressed as R = ρL / S, where ρ is the conductivity of the winding, S is the cross-sectional area of the winding, and L is the length of the winding. For this reason, it is required to use a winding that is as thick as possible, to have a short circumference, and to wind at a high density.

  In order to respond to the above requirements, instead of the conventional distributed winding, a configuration of concentrated winding in which a winding is wound independently on one tooth of a stator via an insulating material has been adopted. Further, a manufacturing technique is used in which each tooth is divided and the winding is aligned and wound by a winding machine.

  Furthermore, when reducing the winding resistance, there is a demand for reducing the thickness of the insulating material between the tooth and the winding conductor. If the winding can be wound around the insulating material space of the stator slot, a thicker winding can be wound and copper loss can be reduced.

  FIGS. 1 to 3 are views showing a comparative example 1. FIG. 1 is a cross-sectional view of the electric motor 200, FIG. 2 is a view showing one tooth portion of the stator 210 of FIG. 1, and FIG. (A) is a cross-sectional view, (b) is an AA cross-sectional view of (a).

  As shown in FIG. 1, the electric motor 200 (brushless DC motor) of Comparative Example 1 includes a stator 210 and a rotor 220.

  The stator 210 includes a stator core 211, a winding 212, and an insulator 213 that insulates the stator core 211 from the winding 212.

  The stator core 211 is formed by annularly forming a plurality of (9 in the example of FIG. 1) tea cores 211a which are divided cores. The tea score 211a is formed by laminating a predetermined number of magnetic steel sheets punched into a predetermined shape, for example, by caulking or the like. The nine tee scores 211a are connected to each other so as to be deformable by, for example, joint wrap (not shown), and the winding 212 is applied in a state (reverse bending) opposite to the normal bending state in FIG. . Before the winding 212 is applied, the insulator 213 is assembled to each tee score 211a. After the winding is completed, the reverse bending state is shaped into the normal bending state, and the stator core 211 is joined by welding or the like to complete the stator 210.

  The insulator 213 is fitted from both end faces of the tea score 211a so as to cover the tea score 211a. As shown in FIG. 3B, the insulators 213a and 213b are fitted from both end surfaces of the tea score 211a in the axial direction. At this time, since a force due to fitting is applied to the insulator 213, the thickness t (see FIG. 2) of the insulator 213 on the side surface portion of the tea score 211a is designed to be about 1 mm in order to ensure strength. Due to the thickness of the insulator 213, the winding cross-sectional area (slot cross-sectional area−insulator cross-sectional area) becomes smaller than the slot cross-sectional area, and the winding diameter has to be reduced. That is, by providing a thick insulator 213 between the winding 212 and the stator core 211 in order to ensure the strength of the insulator 213, the winding resistance is increased and the motor efficiency is deteriorated. The wire diameter of the winding 212 in FIGS. 1 to 3 is, for example, φ0.8 mm.

  In order to solve the above problems, the following configurations were examined. 4 to 6 are diagrams showing a comparative example 2. FIG. 4 is a cross-sectional view of the electric motor 300, FIG. 5 is a diagram showing one tooth portion of the stator 310 in FIG. 4, and FIG. (A) is a cross-sectional view, (b) is a BB cross-sectional view of (a).

  As shown in FIG. 4, the electric motor 300 (brushless DC motor) of Comparative Example 2 includes a stator 310 and a rotor 320.

  The stator 310 of Comparative Example 2 differs from the stator 210 in that a PET (polyethylene terephthalate) film is used as an insulating material in order to increase the winding cross-sectional area.

  As shown in FIG. 4, the stator 310 of Comparative Example 2 also includes a stator core 311, a winding 312, and film insulation 313 that insulates the stator core 311 and the winding 312.

  The stator core 311 has the same configuration as the stator core 211. That is, a plurality of (9 in the example of FIG. 4) tea cores 311a which are divided iron cores are formed in an annular shape. The tea score 311a is formed by laminating a predetermined number of magnetic steel sheets punched into a predetermined shape, for example, by caulking or the like. The nine tee scores 311a are connected to each other so as to be deformable by, for example, a joint wrap (not shown), and the winding 312 is applied in a state opposite to the forward bending state (reverse bending) in FIG. The Before the winding 312 is applied, a film insulation 313 is assembled to each tea score 311a. After the winding is completed, the reverse bending state is changed to the normal bending state, and the stator core 311 is joined by welding or the like to complete the stator 310.

  7 and FIG. 8 are views showing Comparative Example 2. FIG. 7 is a perspective view showing a tea score 311a provided with an end insulator 313-1. FIG. 8 is an end insulator 313- in which the angle seen from FIG. It is a perspective view which shows the tea score 311a which gave 1. The insulating material of the stator 310 according to the first embodiment uses film insulation 313 made of PET film on the side surface portion of the tea score 311a, and the both end surface portions of the tea score 311a are shown in FIGS. An end insulator 313-1 similar to the stator 210 is used. The film insulation 313 made of a PET film and the end insulator 313-1 are fitted (provided with a groove for sandwiching the PET film in the end insulator) and bonded by a method such as adhesion or welding.

  The thickness t1 (see FIG. 5) of the PET film constituting the film insulation 313 is about 0.1 to 0.2 mm, which is about 1/5 to 1/1 compared with the thickness t (about 1 mm) of the insulator 213. It is about 10.

  The end insulator 313-1 is designed with substantially the same shape as the tea score 311a. The end insulator 313-1 is designed so as not to cover a cross-sectional area of a slot (a space formed between adjacent tea cores 311a is called a slot). The end insulator 313-1 is fitted to the end portion of the tea score 311a and joined by a method such as adhesion or welding. In this manufacturing method, the end insulator 313-1 does not affect the slot area. With this configuration, the insulation thickness of the inner periphery of the slot (thickness t1 of the film insulation 313) can be reduced, and the winding cross-sectional area can be increased.

  The winding 312 of the stator 310 of FIG. 4 was able to increase the wire diameter to φ0.95 mm with the same number of turns as the stator 210 of FIG. Since the wire diameter of the winding 212 of the stator 210 is φ0.8 mm, φ0.8 mm → φ0.95 mm, that is, wire diameter +0.15 mm was made possible.

  At this time, the thickness t2 (see FIG. 6B) of the end insulator 313-1 is about 5 mm. The end insulator 313-1 is designed with a predetermined R at the corner. Since the winding 312 must be bent at the end of the core, a certain amount of R is required, and it is not preferable to use a thin film insulation. Further, since the pressure of the winding 312 acts on the end of the core that is narrower than the side surface of the tee score 311a, it is better to give the end insulator 313-1 thicker. Also from this point, the end insulator 313-1 is preferable to the thin film insulation.

FIG. 9 shows the characteristics of the stator 210 of Comparative Example 1 (insulation on the side surface of the tee score 211a is constituted by the insulator 213) and the stator 310 of Comparative Example 2 (insulation on the side surface of the tea score 311a is constituted by the film insulation 313). FIG. In the stator 310 of Comparative Example 2, since the insulation on the side surface of the tea score 311a is configured by the film insulation 313, the insulation thickness on the side surface of the tea score is 1 mm → 0.2 mm (the thickness of the PET film constituting the film insulation 313) t1 (see FIG. 5) is about 0.1 to 0.2 mm, but is 0.2 mm here). Along with that, the winding, motor characteristics, and stray capacitance change as shown below.
(1) Winding cross-sectional area increased by 40%;
(2) Copper loss is reduced by 30%;
(3) 1.5% improvement in motor efficiency;
(4) The floating capacitance between the winding and the stator core increased from 450 to 900 pF.
As described above, in the stator 310 of the comparative example 2, the motor efficiency is improved by 1.5% by configuring the insulation of the side surface of the tea score 311a with the film insulation 313, but the floating between the winding and the stator core is improved. The capacitance increases about twice (450 → 900 pF) compared to Comparative Example 1. This caused the following leakage current problem.

  Leakage current is caused by the presence of stray capacitance between the conductor (winding) in the slot and the stator core. The principle of the leakage current is the same as that of the capacitor. When the leakage current is i, the frequency is f, the capacitance is C, and the voltage is V, the relationship of i = 2πfCV is established.

  Further, the capacitance C between the winding and the stator core is expressed as follows. The dielectric constant between the winding and the stator is ε, the contact area between the winding and the stator is S, and the distance between the winding and the stator is d. Then, a relationship of C = εS / d is established. That is, when a thin insulating material is used, the distance d between the winding and the stator is reduced, the capacitance C is increased, and the leakage current i is liable to flow.

  In addition, inverter driving is frequently used in recent motors because variable speed driving is performed. However, in PWM control such as an inverter, current is generated by high-frequency switching, so that frequency f is high and leakage current tends to flow. The higher the frequency of switching, the higher the waveform generation rate of the motor current. Therefore, there is an advantage that the harmonic component of the current is reduced, and the copper loss and the harmonic iron loss can be reduced. In particular, when switching is performed at a high frequency, the switching loss of the inverter is increased. However, when a device with a small current loss such as SiC (details will be described later) is used, the merit of switching at a high frequency is great. Therefore, there is a strong demand for reducing the leakage current.

  The present invention reduces the copper loss by using a thin insulating material such as a PET film for a stator that is divided and wound (concentrated winding) for a motor that is driven at a variable speed by PWM control such as an inverter. The present invention relates to a motor (electric motor) that can reduce stray capacitance without reducing efficiency and suppress leakage current, and achieves both performance and reliability.

  10 to 12 show the first embodiment. FIG. 10 is a cross-sectional view of the electric motor 100, FIG. 11 is a cross-sectional view of the stator 110, and FIG. 12 is a view showing one tooth portion of FIG. . The electric motor 100 and the stator 110 according to the first embodiment will be described with reference to FIGS. 10 to 12.

  As shown in FIG. 10, the electric motor 100 (brushless DC motor) according to the first embodiment includes a stator 110 and a rotor 120 arranged on the inner periphery of the stator 110. Since the present embodiment is characterized by the stator 110, the stator 110 will be described in detail. The rotor 120 is a six-pole permanent magnet rotor, and is an embedded permanent magnet rotor in which a permanent magnet is inserted into a magnet insertion hole. Other explanations are omitted.

  As shown in FIGS. 11 and 12, the stator 110 includes a stator core 111, a winding 112, and film insulation 113 that insulates the stator core 111 and the winding 112.

  FIGS. 13 and 14 show the first embodiment. FIG. 13 is a cross-sectional view of the stator core 111 and FIG. 14 is a perspective view of the stator core 111. FIG.

  The stator core 111 is formed by annularly forming a plurality of (9 in the example of FIG. 13) tea cores 111a (divided teeth), which are divided cores. The tea score 111a is formed by stacking a predetermined number of, for example, caulking or the like, thin electromagnetic steel sheets punched into a predetermined shape, for example, having a thickness of 0.35 mm. The nine tee scores 111a (divided teeth) are connected to each other so as to be deformable by, for example, joint wraps (not shown), and are wound in a state (reverse bending) opposite to the normal bending state in FIG. Is given. Before the winding 112 is applied, the film insulation 113 is assembled to each tee score 111a (divided teeth). After the winding is completed, the reverse bending state is changed to the normal bending state, and the stator core 111 is joined by welding or the like to complete the stator 110.

  In the stator core 111, a space between adjacent tee scores 111a is referred to as a slot 114. The winding 112 is directly wound around each tee score 111a (divided teeth). As a result, the winding 112 is housed separately in the slot 114 at both ends. Further, the iron core portion between the slots 114 is referred to as a tooth 116. The teeth 116 are a part of the tea score 111a. The stator core 111 has nine slots 114 and nine teeth 116. Further, a ring-shaped (annular) core portion formed on the outer periphery of the stator core 111 is referred to as a core back 115.

  FIG. 15 shows the first embodiment, and is a plan view of the tea score 111a. As shown in FIG. 15, each tooth 116 is configured such that the slot bottom 114a of the slot 114 is substantially perpendicular to the tooth side surface 116a. Then, a groove 114a-1 having a predetermined shape (here, the cross section is rectangular) is provided on the slot bottom side of the slot 114 that is substantially perpendicular to the tooth side surface 116a. In this respect, the present embodiment has the greatest feature. The groove 114a-1 is formed over the entire length of the tea score 111a. The depth (radial direction) of the groove 114a-1 is, for example, 0.6 mm. Further, the region provided with the groove 114a-1 is about 30% of the inner periphery of the slot.

  FIG. 16 shows the first embodiment, and is a plan view of the stator core 111 developed in a band shape. As shown in FIG. 16, in the stator core 111, nine teascores 111a are connected by joint portions 111a-5 (which may be connected by pins or may be connected by unevenness). Therefore, the stator core 111 is deformable.

  FIG. 17 is a diagram showing the first embodiment, and is a plan view showing a state where the stator core 111 is reversely bent so that the teeth 116 are outside and wound. As shown in FIG. 17, when the winding 112 is applied to the stator core 111, the stator core 111 is reversely bent so that the teeth 116 are on the outside, and the winding between the teeth 116 is easily formed. To do. Although FIG. 17 shows the case where the winding 112 is applied to one tee score 111a, the winding 112 is actually applied to all the tee scores 111a in succession.

  Next, the drive circuit 1 of the electric motor 100 will be described. FIG. 18 is a diagram illustrating the first embodiment, and is a circuit diagram of the drive circuit 1 of the electric motor 100. 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 to an AC voltage having a variable frequency by the inverter main circuit 4 and applied to the electric motor 100. The electric motor 100 is driven by variable frequency AC power 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 and a smoothing capacitor that smoothes the rectified DC voltage.

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

  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 with epoxy resin and packaged. The IGBTs 6a to 6f may be IGBTs using SiC or GaN instead of IGBTs using silicon (Si-IGBT), and MOSFETs (Metal-Oxide-Semiconductor Field-) using Si, SiC, or GaN instead of IGBTs. Other switching elements such as 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 the high-voltage DC voltage is reduced by the voltage-dividing circuit using the voltage-dividing resistors 8a and 8b. A DC voltage detector 8 is provided for sampling and holding the electrical signal.

  In addition, the electric motor 100 includes a stator 110 and a rotor 120, and the rotor 120 is rotated by AC power supplied from the inverter main circuit 4.

  A rotor position detection unit 10 that detects the terminal voltage of the electric motor 100 and detects the position of the rotor 120 of the electric motor 100 is provided. The rotor position detection unit 10 processes the electrical signal of the terminal voltage of the electric motor 100 and converts it into position information of the rotor 120.

  The position information of the rotor 120 detected by the rotor position detection unit 10 is output to the output voltage calculation unit 11. This output voltage calculation unit 11 is an optimum inverter main unit to be applied to the electric motor 100 based on the command of the target rotational speed N given from the outside of the drive circuit 1 or information on the operating conditions of the device and the position information of the rotor 120. The output voltage of the circuit 4 is calculated. The output voltage calculation unit 11 outputs the calculated output voltage to the PWM signal generation unit 12. PWM is an abbreviation for Pulse Width Modulation.

  The PWM signal generation unit 12 outputs a PWM signal that becomes the output voltage given from the output voltage calculation unit 11 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 The four IGBTs 6a to 6f are respectively switched by the main element drive circuit 4a.

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

  Further, the electric motor 100 performs high-efficiency operation in accordance with required product load conditions by performing variable speed driving by PWM control by the inverter (inverter main circuit 4) of the driving circuit 1. The switching carrier of the inverter has a waveform generated at, for example, 4.5 kHz, and the driving voltage includes a high frequency due to switching higher than the operating frequency. During high-frequency operation by PWM control, leakage current is likely to flow due to the presence of stray capacitance between the conductor (winding 112) in the slot 114 and the stator core 111. The principle of the leakage current is the same as that of the capacitor. When the leakage current is i, the frequency is f, the capacitance is C, and the voltage is V, the relationship of i = 2πfCV is established.

  The stator 110 is configured as shown in FIG. 11, and a winding 112 is wound by concentrated winding (direct winding on the teeth 116) via a thin PET film insulation 113. The thickness of the PET film is, for example, about 0.1 to 0.2 mm.

  Further, end insulators (the same as the end insulator 313-1 (FIGS. 7 and 8)), which are insulating materials, are also disposed at both axial ends of the stator core 111.

  The film insulation 113 (PET film) disposed on the side surface of the tea score 111a and the end insulator of the end portion of the tea score 111a are joined so as not to have a gap by fitting, bonding, welding, or the like.

  The windings 112 of the stator 110 are wound by the flyer along the side surfaces of the teeth 116 of the divided tea score 111a, and are lined up one by one and stacked in a bowl shape. That is, when viewed in the cross section of the slot 114, the pressure of the winding 112 is applied to the tooth side surface 116a, and not applied to the slot bottom side 114a that is substantially perpendicular to the side surface of the tooth 116.

  That is, even if the groove 114a-1 is provided in the slot bottom 114a, a high-density winding can be performed while maintaining the alignment without affecting the winding property. In particular, since the thin film insulation 113 (PET film) is used for the insulation, a sufficient winding cross-sectional area can be secured in the slot 114, and the resistance can be reduced by using a thick winding. Loss can be reduced and the highly efficient electric motor 100 can be comprised.

  At this time, since the distance between the stator core and the winding is reduced in the case of a normal stator core (for example, the stator core 211 of Comparative Example 1 and the stator core 311 of Comparative Example 2), the stator core is reduced. As a result, there arises a problem that the stray capacitance between the windings increases and the leakage current increases.

  However, by forming the stator core 111 as in the present embodiment (providing the groove 114a-1 on the slot bottom 114a), a gap due to the groove 114a-1 is secured between the slot bottom 114a and the winding 112. The Thereby, the contact area between the winding 112 and the stator core 111 is reduced, the distance between the winding 112 and the stator core 111 is increased, and the floating capacitance between the winding 112 and the stator core 111 is reduced. be able to.

  The point is that no groove is provided on the tooth side surface 116a to which the pressure of the winding 112 is applied by concentrated winding (direct winding on the tooth 116). In addition, the provision of the groove 114a-1 in the slot base 114a that is substantially perpendicular to the tooth side surface 116a is a device for ensuring the air gap by the groove 114a-1 without deteriorating the winding property. Thereby, the leakage current can be reduced, and the highly reliable electric motor 100 can be configured.

  FIG. 19 is a diagram showing the first embodiment, and is a diagram showing measurement results of stray capacitance between the stator core and the windings of the conventional and the present embodiment. When the prototype of the stator 110 according to the present embodiment was actually prototyped, a conventional grooveless stator (for example, the stator core 311 of Comparative Example 2) was subjected to the same insulating material and winding conditions. The stray capacitance between the winding 112 and the stator core 111 was reduced from 900 pF to 700 pF, and a reduction effect of about 23% could be confirmed. In addition, no winding disturbance was found, and a winding property with a high space factor was realized. In addition, the leakage current reduction effect in the compressor proportional to the decrease in the floating capacitance could be confirmed.

  The stator core 111 has a role of a magnetic path as an iron core. However, if the groove 114a-1 is provided in the stator core 111, the magnetic path is narrowed and magnetic characteristics are deteriorated.

  The magnetic flux passes from the rotor 120 through the teeth 116, is separated by the core back 115, and returns to the rotor 120 through the teeth 116. When considering the magnetic characteristics, the ease of passing the magnetic flux is determined by the narrowest part of the magnetic path. Therefore, it is not preferable to narrow the magnetic path of the tooth 116 that is the inlet of the magnetic flux, and no groove is provided on the tooth side surface 116a.

  FIG. 20 is a diagram showing the first embodiment, and is a plan view of the tea score 111a. In the tee score 111a of the present embodiment, the slot base 114a is provided at a substantially right angle with respect to the tooth side surface 116a in consideration of the winding property, and therefore the magnetic path of the core back 115 is not uniform. That is, the configuration is such that the magnetic path is minimized on the teeth dividing surface (the dividing surface of the tea score 111a). Since the ease of passing the magnetic flux is determined by the narrowest part Wmin of the magnetic path, the groove 114a-1 is provided in the part where the magnetic path of the core back 115 is wide so that the minimum magnetic path is not narrowed (W ≧ Wmin). preferable. By doing so, the air gap between the winding 112 and the stator core 111 can be secured without greatly deteriorating the magnetic characteristics, and the electric motor 100 that is excellent in terms of efficiency with the effect of reducing leakage current can be configured. it can.

  FIG. 21 is a diagram showing the first embodiment, and is a plan view of the tea score 111a-1 of the first modification. As described above, the ease of passing the magnetic flux is determined by the narrowest portion Wmin of the magnetic path, so that even if W = Wmin, the magnetic characteristics are not greatly deteriorated. Therefore, the groove 114a-2 as shown in FIG. 21 is a preferable shape. The bottom of groove 114a-2 is formed along a circle that passes through the intersection on the inside of the teeth division surface (division surface of tea score 111a) that minimizes the magnetic path. By the groove 114a-2, the gap between the winding 112 and the stator core 111 is increased, and the floating capacitance can be reduced without greatly deteriorating the magnetic characteristics.

  FIG. 22 is a diagram showing magnetic flux line analysis results of a motor having no groove in a conventional slot, FIG. 23 is a diagram showing magnetic flux line analysis results of an electric motor having a slot in the present embodiment, and FIG. 24 is a conventional slot. It is the figure which compared the characteristic of the electric motor which does not have a groove | channel, and the electric motor which provided the groove | channel in the slot of this Embodiment.

  When the loss analysis was actually performed by the electromagnetic field analysis, there was no change in the magnetic flux inflow amount (see FIGS. 22 and 23), and no influence on the copper loss was seen (see FIG. 24). Regarding iron loss, an increase was observed because the magnetic flux density partially increased, but it was a slight increase of 0.9%, and it was confirmed that the effect on the motor efficiency was very small with a decrease of 0.03% ( (See FIG. 24). Even in the actual motor test, the decrease in efficiency was 0.0% and had no effect.

  In the present embodiment, the leakage current can be reduced only by the structure in the slot 114 of the stator 110 (the groove 114a-1 is provided in the slot bottom 114a), which is excellent in terms of manufacturing and cost such as assembly. Yes.

  FIGS. 25 and 26 are diagrams showing the first embodiment. FIG. 25 is a plan view of the tee score 111a-2 according to the second modification. FIG. 26 is a diagram illustrating the tee score 111a-2 according to the second modification. It is a figure which shows a state.

  As in the tea score 111a-2 of the second modification, the film insulation 113 (PET film) and the winding 112 are less likely to enter the groove 114a-3 by dispersing the groove 114a-3 in a plurality, and more reliably. In addition, a gap between the winding 112 and the stator core 111 can be secured, and the floating electrostatic capacity can be reduced. That is, the winding 112 is wound so as to press the teeth side surface 116a. However, as the winding 112 is wound up, the stacked winding 112 may be crushed down to the slot bottom 114a. In this case, the pitch of the grooves 114a-3 is reduced. If the length is shorter, the winding 112 is less likely to enter and it is easier to ensure an insulation distance. Although FIG. 25 shows a shape in which the groove 114a-3 is divided into two parts, the groove may be further divided into a plurality of parts.

  FIGS. 27 and 28 are diagrams showing the first embodiment. FIG. 27 is a plan view of the tee score 111a-3 according to the third modification. FIG. 28 is a diagram illustrating the tee score 111a-3 according to the third modification. It is a figure which shows a state. The tee score 111a-3 of Modification 3 is such that a concave and convex shape is provided on the slot bottom 114a, and the concave and convex portion is a groove 114a-4. Even if the winding 112 enters the groove 114a-4, the contact area between the winding 112 and the stator core 111 is reduced, and the gap between the winding 112 and the stator core 111 is more reliably secured and floated. Capacitance can be reduced. Further, in terms of the contact area between the film insulation 113 (PET film) and the stator core 111, a shape in which the contact portions of both of them protrude toward the inner periphery of the slot 114 is preferable because the contact area can be reduced.

  FIGS. 29 to 31 are diagrams showing the first embodiment. FIG. 29 is a perspective view of the stator core 411 according to the fourth modification. FIG. 30 is a tea score that is a divided tooth constituting the stator core 411 according to the fourth modification. FIG. 31 is a plan view of the first tea score plate 411a-1 and the second tea score plate 411a-2 constituting the tea score 411a ((a) is the first tea score plate 411a-1). (B) is the 2nd tea score board 411a-2).

  The groove on the bottom side of the slot can also be formed in the axial direction of the stator core by stacking two teascores having different core back shapes.

  A stator core 411 of Modification 4 shown in FIG. 29 is formed by combining nine tea scores 411a that are divided teeth shown in FIG. In the stator core 411, nine slots 414 are formed between nine tee scores 411a. Further, between the nine slots 414, teeth 416 are formed extending radially in the radial direction. The teeth 416 are a part of the tea score 411a. In addition, a ring-shaped (annular) core back 415 that is connected to the outer end of the teeth 416 is formed.

  For example, as shown in FIG. 30, the tea score 411a is formed by alternately stacking first tea score plates 411a-1 and second tea score plates 411a-2. The length A of the core back of the first tea score plate 411a-1 is approximately 0.6 mm longer than the length B of the core back of the second tea score plate 411a-2 (see FIG. 31). Therefore, a groove 414a-1 (see FIG. 30) is formed between the first tea score plates 411a-1.

  Also in the stator core 411 of the modified example 4, the width of the teeth is the same for both (first tea score plate 411a-1 and second tea score plate 411a-2) (C dimension in FIG. 31). Accordingly, the groove 414a-1 (see FIG. 30) is provided at the bottom of the slot 414 of the core back 415. The reason is as already described in the description of the stator core 111. The configuration of the PET film and the end insulator is the same as that of the stator 110. In the fourth modification, the same floating capacitance reduction effect as that of the stator 110 is confirmed, and there is a leakage current reduction effect.

  In the present embodiment, leakage current can be reduced in a motor (motor) operating at high frequency in PWM control such as an inverter.

  FIG. 32 is a diagram showing the first embodiment, and is a diagram showing a current waveform when the inverter is driven. FIG. 32 is an example of a current waveform when the electric motor 100 is driven by the drive circuit 1. Since the leakage current tends to flow as the switching frequency of the inverter becomes higher, it is effective as a countermeasure against leakage current of a motor that switches at high speed with a device such as SiC, particularly a motor that drives the inverter carrier at 4 kHz or higher.

  When the electric motor according to the present embodiment is used in a refrigerant such as a compressor, R32 refrigerant or the like particularly has a large dielectric constant, so that it becomes a more effective countermeasure against leakage current.

  As an application example of the present invention, in a motor used in a compressor for an air conditioner, it is possible to make the insulating material thinner, reduce copper loss, and provide a highly efficient motor. Furthermore, it is effective as a countermeasure against leakage current in the refrigerant (R32) having a high dielectric constant of the compressor, and is also effective as a countermeasure against leakage current in inverter driving that performs high-frequency switching such as SiC. Can be diversified.

  1 drive circuit, 2 commercial AC power supply, 3 rectifier circuit, 4 inverter main circuit, 4a main element drive circuit, 6a to 6f IGBT, 7a to 7f SiC-SBD, 8a voltage dividing resistor, 8b voltage dividing resistor, 10 rotor position Detection unit, 11 Output voltage calculation unit, 12 PWM signal generation unit, 100 motor, 110 stator, 111 stator core, 111a tee score, 111a-1 tee score, 111a-2 tee score, 111a-3 tee score, 111a -5 joint, 112 winding, 113 film insulation, 114 slot, 114a slot bottom, 114a-1 groove, 114a-2 groove, 114a-3 groove, 115 core back, 116 teeth, 116a teeth side surface, 120 rotor, 200 Electric motor, 210 Stator, 211 Stator core, 2 1a Tea Score, 212 Winding, 213 Insulator, 213a Insulator, 213b Insulator, 220 Rotor, 300 Electric Motor, 310 Stator, 311 Stator Core, 311a Tea Score, 312 Winding, 313 Film Insulation, 313-1 End Insulator, 320 rotor, 411 stator core, 411a tee score, 411a-1 first tee score plate, 411a-2 second tee score plate, 414 slot, 415 core back, 416 teeth.

Claims (7)

In a stator of an electric motor driven at a variable speed by PWM (Pulse Width Modulation) control,
A stator core composed of a plurality of divided cores each having teeth, and a slot formed between the teeth of each divided core ;
Winding wound around each split iron core in a concentrated winding method;
Film insulation that insulates between the winding and the inner peripheral portion of the slot including the side of the tooth of each divided iron core and the bottom of the slot that is substantially perpendicular to the side of the tooth ;
An end insulator that insulates between the winding and the axial ends of the teeth of each of the divided cores;
With
The stator iron core is formed with a groove having a predetermined shape on the bottom side of the slot,
The stator of an electric motor, wherein the film insulation and the end insulator are joined so that there is no gap . The stator iron core, a stator of the electric motor according to claim 1, wherein the grooves are substantially uniformly forming a plurality along a direction forming a side portion substantially perpendicular teeth of each segment core. Said stator core, said wavy irregularities on the bottom of the slot are provided, the stator of the electric motor according to claim 2, wherein the groove is characterized by being formed in the recess of the concave convex. The stator core includes an annular core back in the circumferential direction outwardly of the slot, as the magnetic path width W before SL core back, not narrower than the shortest magnetic path Wmin of the core back, the groove shape the stator of the electric motor according to any one of claims 1 to 3, characterized in that it is formed. The stator core includes an annular core back in the circumferential direction outwardly of the slot, in Rukoto radially of two kinds lengths of the electromagnetic steel plates of the core back is laminated, that the groove is formed the stator of the electric motor according to claim 1 or 4, wherein. The stator of the electric motor according to any one of claims 1 to 5, characterized in that it is applied to a motor driven by a drive circuit using the device using SiC (silicon carbide) on the switching unit of the inverter main circuit. The electric motor stator according to any one of claims 1 to 6 , wherein the electric motor stator is mounted on an air conditioning compressor and driven in a refrigerant (R32) having a high dielectric constant.

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