Motors for air compressors

Abstract

The present disclosure provides a motor for an air compressor. The motor includes: a stator including a first coil generating magnetic flux for driving the motor and a second coil located in the same space as the first coil to increase inductance; and a rotor interacting with the stator to rotate.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2019-0141279 filed on November 6, 2019, in the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to a motor for an air compressor. Background Art

[0004] The fuel cell system applied to environmentally friendly vehicles provides electrical energy generated by the chemical reaction of hydrogen and air as a driving force. The fuel cell system includes an air processing system (APS) to supply external air to the fuel cell stack. The APS includes an air filter, an air compressor, a humidifier and an air blocker. Among them, the air compressor has the largest volume among the various components that drive the fuel cell, resulting in a higher volume limitation. Therefore, traditionally, a high-speed motor of 90krpm or higher has been applied to the air compressor to reduce the volume of the air compressor, and thus a low inductance is formed on the high-speed motor.

[0005] Traditionally, air compressors that apply high-speed motors directly use power from the fuel cell stack as input power, resulting in voltage limitations. Therefore, the inductance is designed to have a low value ranging from tens of μHs to hundreds of μHs. However, low inductance increases the peak current through the inverter switch to increase the current pulsation input to the motor. The increase in current pulsation leads to increased losses, which brings difficulties to the cooling design of the motor and inverter. To solve this traditional problem, the inductance can be increased by using the coil required to drive the motor, but the characteristics of the motor may be changed.

[0006] Alternatively, an external inductor (coil) may be provided between the inverter and the motor to increase the inductance without changing the motor characteristics. However, when an external inductor is provided, a separate cooling device is also required to cool the heat generated by the external inductor, resulting in increased costs. Summary of the invention

[0007] An object of the present disclosure is to solve the above-mentioned problems arising in the prior art while excellently maintaining the advantages achieved by the prior art.

[0008] One aspect of the present disclosure provides a motor for an air compressor, in which inductance is increased by adding a coil inside the motor.

[0009] The technical problems to be solved by the present disclosure are not limited to the above-mentioned problems, and any other technical problems not mentioned in the present disclosure will be clearly understood by those skilled in the art to which the present disclosure belongs from the following description.

[0010] According to one aspect of the present disclosure, a motor for an air compressor includes a stator including a first coil generating magnetic flux for driving a motor and a second coil located in the same space as the first coil to increase inductance; and a rotor rotating in interaction with the stator.

[0011] The second coil is additionally wound so as to overlap with the first coil wound on the stator.

[0012] The second coil includes three pairs of coils having different phases from each other.

[0013] Each of the three pairs of coils includes two coils disposed opposite to each other.

[0014] The two coils are wound in opposite directions to each other to cancel out the magnetic flux generated towards each other.

[0015] The rotor includes N-pole permanent magnets and S-pole permanent magnets attached to the surface of the rotor. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description in conjunction with the accompanying drawings:

[0017] Figure 1 is a view schematically showing a motor according to an embodiment of the present disclosure.

[0018] Figure 2 is a view illustrating a method of winding a second coil in a motor according to an embodiment of the present disclosure.

[0019] Figure 3 is a graph showing performance of a motor according to an embodiment of the present disclosure.

[0020] Figure 4 is another graph illustrating the performance of a motor according to an embodiment of the present disclosure.

[0021] Reference numerals:

[0022] 100: Motor;

[0023] 110: rotor;

[0024] 111: N-pole permanent magnet;

[0025] 112: S-pole permanent magnet;

[0026] 120: stator;

[0027] 121: teeth;

[0028] 122: slot;

[0029] 130: first coil;

[0030] 140: Second coil. DETAILED DESCRIPTION

[0031] Hereinafter, some embodiments of the present disclosure will be described in detail with reference to the exemplary drawings. When adding reference numerals to the components of each drawing, it should be noted that the same or equivalent components are designated by the same reference numerals even if they are shown on other drawings. In addition, when describing the embodiments of the present disclosure, detailed descriptions of known features or functions will be omitted to avoid unnecessarily obscuring the purpose of the present disclosure.

[0032] When describing components according to embodiments of the present disclosure, terms such as first, second, "A", "B", (a) and (b) may be used. These terms are intended only to distinguish one component from other components, and the terms do not limit the nature, order or sequence of the components. Unless otherwise defined, all terms used herein, including technical terms or scientific terms, have the same meanings as those commonly understood by those skilled in the art to which the present disclosure belongs. Terms such as those defined in commonly used dictionaries should be interpreted as meanings consistent with the contextual meanings of the relevant technical field, and should not be interpreted as having idealized or overly formalized meanings unless explicitly defined in this application as having such meanings.

[0033] The present disclosure relates to a motor (high-speed motor) driving an air compressor in an air handling system (APS) of a fuel cell vehicle, and proposes a method of increasing inductance without changing motor characteristics.

[0034] Generally speaking, air compressors should be made as small as possible to fit in APS applications. The size of an air compressor is greatly affected by the size of the motor, and the size of the motor is proportional to the motor torque. Therefore, when designing an air compressor, the motor speed should be increased as much as possible while the motor torque should be reduced as much as possible.

[0035] Because the battery voltage decreases when the output of the fuel cell stack increases, the output and speed of the air compressor are determined by considering the maximum flow rate corresponding to the maximum output of the fuel cell stack when designing the air compressor. In other words, the maximum speed will be generated when the maximum flow rate is required, and at this time, the driving voltage of the air compressor is also the minimum. For example, if the voltage is 200V when the fuel cell stack is at maximum output, the air compressor should meet the maximum speed and maximum output (= torque × speed) at 200V voltage.

[0036] When designing a motor taking into account the characteristics of a fuel cell stack and an air compressor, there may be many limitations. The parameters that define the motor characteristics include resistance R, inductance L, back electromotive force (BackEMF), torque T, speed ω, and input voltage V.

[0037] The motor characteristics can be expressed as the following equations 1 and 2. To characterize the motor, the voltage V, inductance L, and current i generated in the motor are separated by the dq axis of the rotating orthogonal coordinate system. The d axis is the axis that generates the magnetic flux of the motor, and the q axis is the axis orthogonal to the d axis.

[0038] Equation 1

[0039] V d =(R a +pL d )i d +(-ωL q )i q

[0040] Equation 2

[0041] V q =(ωL d )i d +(R a +pL q )i q +ωφ a

[0042] Among them, V d represents the d-axis voltage, V q represents the q-axis voltage, L d Indicates the d-axis inductance, L q represents the q-axis inductance, i d represents the d-axis current, i q represents the q-axis current, R a Represents winding resistance, φ a Indicates the back EMF generated by the magnetic flux. When using surface permanent magnets (SPM), L d and L q The resistor R a The inductance L is determined by the length of the winding (coil), and the inductance L is determined by the number of turns of the winding (coil) on the stator. When the input voltage V of the motor is higher than V d and V q The root value of the sum of the squares of each The motor can only operate normally when the motor is small. In order to make the motor size smaller when the input voltage of the motor is small, various parameters should be designed to be as small as possible. Among them, the inductance is designed to be as small as possible. However, when the inductance is designed to be smaller, the smaller inductance will increase the current pulsation input to the motor, thereby increasing the loss, which will cause cooling problems in the motor and the inverter. Therefore, in order to solve the problems caused by the smaller inductance, the present disclosure proposes a motor that increases the inductance by adding a coil inside the motor without affecting the characteristics of the motor. The inductance in the motor is a parameter that generates magnetic flux by the current input to the motor. Therefore, the larger the inductance, the larger the magnetic flux can be generated even at a smaller input current. The inductance of the inverter is intended to prevent the current from changing when it flows in the wire (coil). The larger the inductance, the peak current can be reduced by the inverter switch, thereby reducing the current pulsation.

[0043] Figure 1 is a view schematically showing a motor according to an embodiment of the present disclosure, Figure 2 is a view showing a method of winding a second coil in a motor according to an embodiment of the present disclosure. According to the present embodiment, a surface permanent magnet (SPM) motor in which permanent magnets are attached to a rotor surface will be described below.

[0044] Reference Figure 1 , the motor 100 includes a rotor 110 and a stator 120 .

[0045] The rotor 110 includes an N-pole permanent magnet 111 and an S-pole permanent magnet 112 attached to the rotor surface. The rotor 110 is rotatably disposed with a predetermined distance (i.e., an air gap) from the stator 120. The rotor 110 rotates by interaction with the stator 120. In this case, the rotor 110 rotates around an axis as a drive axis.

[0046] The stator 120 is disposed outside the rotor 110 and is fixedly disposed inside the motor housing. The stator 120 includes a plurality of teeth 121 that protrude radially while being spaced apart from each other by a predetermined distance in the circumferential direction of the body. Slots 122 are formed between the teeth 121. The slots 122 are spaces where the coils wound on the teeth 121 are located.

[0047] The first coil 130 and the second coil 140 are wound around the tooth 121. The first coil 130 includes a first coil 131 having a first phase (U phase), a first coil 132 having a second phase (V phase), and a first coil 133 having a third phase (W phase). When current is input from an inverter (not shown), the first coil 130 generates a first magnetic flux for driving the motor. The direction of the first magnetic flux generated in the winding direction of the first coil 130 according to Fleming's right-hand rule is as follows: Figure 2The first magnetic flux generated by the stator 120 interacts with the magnetic force of the N-pole permanent magnet 111 and the S-pole permanent magnet 112, so that the rotor 110 rotates.

[0048] The second coil 140, which is a coil (additional coil) added to increase inductance, is arranged to overlap the first coil 130. The second coil 140 is located in the same slot 122 as the first coil 130. The second coil 140 may include three pairs of coils having different phases from each other, and may include, i.e., a pair of second coils 141A and 141B having a first phase, a pair of second coils 142A and 142B having a second phase, and a pair of second coils 143A and 143B having a third phase. The pair of second coils 141A and 141B having the same phase are arranged opposite to each other, the pair of second coils 142A and 142B having the same phase are arranged opposite to each other, and the pair of second coils 143A and 143B having the same phase are arranged opposite to each other.

[0049] In order to increase the inductance of the motor 100, the number of turns of the second coil 140 is increased. In this case, the number of turns of the second coil 140 can be determined by the size of the slot 122. A pair of second coils 141A and 141B having the same phase and arranged opposite to each other are wound in directions (winding directions) opposite to each other to cancel out the second magnetic flux generated from the pair of second coils 141A and 141B having the first phase. A pair of second coils 142A and 142B having the same phase and arranged opposite to each other are wound in winding directions opposite to each other to cancel out the second magnetic flux generated from the pair of second coils 142A and 142B having the second phase. A pair of second coils 143A and 143B having the same phase and arranged opposite to each other are wound in winding directions opposite to each other to cancel out the second magnetic flux generated from the pair of second coils 143A and 143B having the third phase. In other words, the winding directions of a pair of second coils 141A and 141B, 142A and 142B, or 143A and 143B of each phase are opposite to each other.

[0050] More specifically, if Figure 1 As shown, a second coil 140 for increasing inductance is further wound around the stator 120. Figure 2 As shown, the method of winding the second coil 140 is to wind the second coils symmetrically placed in opposite directions. In this case, "⊙" indicates that the second coil 140 is wound upward in the slot 122. It is shown that the second coil 140 is wound downward in the slot 122. As described above, the second magnetic fluxes are generated by the second coil 140 of each phase in opposite directions to each other and cancel each other out, thereby not affecting the motor operation.

[0051] As described above, the first coil 130 required for driving the motor and the second coil 140 required for increasing the inductance are provided in the same slot 122. Therefore, the existing motor cooling device can be used to cool the heat generated from the second coil 140. As described above, the existing motor cooling device can be shared, which is advantageous in the layout configuration of the vehicle.

[0052] Figure 3 and Figure 4 is a graph showing performance of a motor according to an embodiment of the present disclosure.

[0053] Reference Figure 3 When the same input current is applied to the motor 100 according to the present disclosure and the conventional motor, the motor 100 according to the present disclosure has an increased induced voltage compared to the conventional motor. In other words, the motor 100 according to the present disclosure has an increased induced voltage due to the increased inductance through the second coil 140.

[0054] Reference Figure 4 , at the same speed, the motor 100 according to the present disclosure outputs a torque similar to that of a conventional motor. The output of the motor (=rotation speed×torque) is defined as the rotation speed and torque of the motor. Figure 4 , the motor 100 according to the present disclosure has no difference in performance from a conventional motor.

[0055] As described above, although the second coil 140 is added to the inside of the motor 100 to increase the inductance through the second coil 140, it has no effect on the driving (characteristics) of the motor 100. When the inductance is increased through the second coil 140, the pulsation of the current input to the motor 100 is reduced, thereby improving the efficiency of the air compressor.

[0056] As described above, according to the present disclosure, when coils are added to increase the inductance within the motor, the winding directions of the additional coils facing each other are opposite, thereby maintaining the motor characteristics.

[0057] In addition, according to the present disclosure, the coils required for driving the motor and the coils required for increasing the inductance are arranged inside the motor. Therefore, the existing motor cooling device can be shared without providing a separate cooling device for cooling the heat generated from the coils required for increasing the inductance.

[0058] In the above, although the present disclosure is described with reference to exemplary embodiments and the accompanying drawings, the present disclosure is not limited thereto, but can be variously modified and changed by a person skilled in the art to which the present disclosure belongs without departing from the idea and scope of the present disclosure claimed for protection by the attached claims. Therefore, the embodiments of the present disclosure are not intended to limit the technical ideas of the present disclosure, but are provided only for illustrative purposes. The scope of protection of the present disclosure should be interpreted by the attached claims, and all equivalent schemes thereof should be interpreted as being included within the scope of the present disclosure.

Claims

1. A motor for an air compressor, include: a stator including a first coil generating a magnetic flux for driving the motor and a second coil located in the same space as the first coil to increase inductance; as well as The rotor, which rotates in interaction with the stator, in: The second coil includes three pairs of coils with different phases from each other, Each of the three pairs of coils includes two coils arranged opposite to each other, and The two coils are wound in opposite directions to each other to cancel out magnetic fluxes generated relative to each other.

2. The motor according to claim 1, in, The second coil is additionally wound to overlap with the first coil wound on the stator.

3. The motor according to claim 1, in, The rotor includes N-pole permanent magnets and S-pole permanent magnets attached to a surface of the rotor.

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