A multi-pair pole wave winding series excited motor for food processing and kitchen small household appliances

Abstract

The application discloses a kind of multi-pair pole, wave winding series excited motor for food processing and kitchen small household appliances, belong to motor technical field, comprising: stator and rotor, stator is provided with multiple excitation windings, rotor is provided with armature winding, excitation winding and armature winding are connected in series, armature winding is wave winding, the number of pole pairs p of stator is greater than or equal to 2.The application increases the effective volume and capacity of motor by the combination of stator multi-pole and armature wave winding, and the number of parallel branches does not increase with the increase of pole pairs, solves the commutation problem of multi-pole series excited motor, so that the performance of motor is fully guaranteed.

Description

Technical Field

[0001] This invention relates to the field of motor technology, specifically to a multi-pole, wave-wound series-excited motor for food processing and small kitchen appliances. Background Technology

[0002] In the food processing and small kitchen appliance industries, such as dough mixers, meat grinders, juicers, slicers, and blenders, as well as their multifunctional machines, the series motors used are generally single-pole, lap-wound series motors. However, this type of motor has a relatively long magnetic circuit and electrical circuit, resulting in a small effective motor volume and a relatively small motor capacity.

[0003] To increase the effective volume and capacity of this type of motor, a small number of series-wound motors with multiple pole pairs in the stator and lapped armature windings have emerged. Compared to a single-pole motor, multiple pole pairs can shorten the magnetic circuit of the yoke and also compress the size of the winding ends, which only serve a connecting function and do not generate effective electromagnetic linkage. This reduces the motor winding impedance and lowers the copper loss, aiming to improve motor efficiency, save copper costs, and ultimately increase the effective volume and capacity of the motor.

[0004] However, due to the inherent defects of the 2-pole, lap-wound series excitation motor, two serious problems will be introduced: 1. Compared to a single-pole motor, the commutation spark increases significantly, the commutation difficulty increases sharply, the motor performance deteriorates severely, and the motor capacity cannot be fully expanded.

[0005] 2. To address the issue of excessive commutation sparking introduced by multi-pole, lap-winding series motors, significant additional material and manufacturing costs are required to achieve the goal of increasing the effective motor volume and, appropriately but not fully, expanding the motor capacity using a two-pole, lap-winding scheme. This results in additional cost increases and waste.

[0006] Therefore, there is an urgent need to design a series motor that can significantly increase the effective volume of the motor, expand its capacity, and save on material and process costs. Summary of the Invention

[0007] In order to overcome the shortcomings of the prior art, the present invention provides a multi-pole, wave-wound series-wound motor for food processing and small kitchen appliances. The aim is to effectively solve the problem of large commutation sparks by combining a multi-pole stator with a wave-wound armature, thereby significantly increasing the effective volume and capacity of the motor.

[0008] To achieve the above objectives, the present invention provides the following solution: A multi-pole, wave-winding series-wound motor for food processing and small kitchen appliances includes: a stator and a rotor. The stator is provided with multiple excitation windings, and the rotor is provided with an armature winding. The excitation windings and the armature windings are connected in series. The armature windings are wave windings, and the number of pole pairs p of the stator is ≥2.

[0009] The present invention also provides a food processing device, including a main unit and a drive motor disposed in the main unit, wherein the drive motor is a multi-pole, wave-wound series-excited motor as described above.

[0010] Compared with the prior art, the present invention discloses the following technical effects: The stator of this invention adopts a multi-pole structure, which can effectively shorten the magnetic circuit and electrical circuit of the yoke, compress the size of the winding end that only serves a connecting function, reduce the winding impedance, reduce copper loss, and further increase the effective volume of the motor and expand the motor capacity. At the same time, the armature winding of this invention adopts a wave winding, so that the number of parallel branches of the armature does not increase with the increase of the number of pole pairs. Thus, when the number of slots in the motor is close, the number of series turns per slot or per element is reduced by a factor of two compared with the lap winding, and the commutation potential of each component is reduced sharply. This effectively solves the commutation problem of series-wound motors with multi-pole stators and lap windings in the armature, and the motor performance is fully guaranteed. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the component shape of a single-lap winding in the prior art; Figure 2 This is an unfolded diagram of a 2-pole, 16-slot, full-pitch single-lap winding in the prior art. Figure 3 This is a schematic diagram of the magnetic circuit of a brush in a single-pole series motor at a certain moment along the geometric center line in the prior art. Figure 4 This is a circuit diagram of a single-pole series motor in the prior art; Figure 5 This is a schematic diagram of the magnetic circuit of the brushes of a two-pole series motor at a certain moment along the geometric center line in the prior art; Figure 6 This is a circuit diagram of a two-pole series excitation motor in the prior art; Figure 7 This is a phasor diagram of a series motor in the prior art; Figure 8This is a wiring diagram of a single-pole series motor with serious defects in the existing technology. Figure 9 This is a wiring diagram of a two-pole series motor, which has serious defects in the existing technology. Figure 10 This is a schematic diagram of the wave winding element of the present invention; Figure 11 This is a circuit diagram of the 2-pole 25-slot wave winding series excitation motor of the present invention; Figure 12 This is a schematic diagram of the unfolded 25-slot wave winding of the two poles of the present invention. Detailed Implementation

[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] I. Background Technical Analysis In the food processing and small kitchen appliance industries, series motors are widely used due to their high speed, small size, and large starting torque. For a long time, this field has primarily employed series motors with a single pole and lapped windings.

[0015] Lap windings are divided into single-lap windings and compound lap windings. Since single-lap windings are the most common in low-power food processing and small kitchen appliances, and the characteristics of compound lap windings can be derived from those of single-lap windings, they will not be explained further here.

[0016] The shape of a single-layer winding is as follows Figure 1 As shown, the two commutator segments connecting the two conductor sides of the same element in a single-layer winding are adjacent. Taking a 2-pole, 16-slot full-pitch winding as an example, its winding development diagram is as follows. Figure 2 As shown, from Figure 2 As can be seen from this, single-lap windings have the following characteristics: (1) Reversing pitch y k =±1. (2) All conductors on the upper element side under the same pole are connected in series and form a parallel branch, that is, the number of parallel branches a=p (number of pole pairs) and the number of parallel branches 2a=2p.

[0017] (3) More parallel branches can be obtained by increasing the number of pole pairs p, so as to carry a larger armature current.

[0018] In a series-wound motor, the stator excitation winding is connected in series with the armature winding via brushes. For the working principle and wiring method of the motor with the brushes positioned at the geometric center line, please refer to [reference needed]. Figure 3-6 .in, Figure 3 In This is the leakage flux, which is generally very small; Let be the direct-axis air gap magnetic flux per pole. In the lap winding, the conductor potentials of the elements under each pole of the armature are in the same direction and are connected in series to form a branch. And so on, the number of parallel branches of the armature is 2p.

[0019] The voltage balance equation for a series-wound motor is: (1) Among them, armature rotation potential for: (2) P is the number of pole pairs, N is the total number of armature conductors, and k p Here, n is the short-pitch coefficient, a is the motor speed, and f is the number of parallel branches of the armature conductors. a The armature rotation frequency, W a W is the total number of series turns in each branch of the armature winding. a =N / 2a; Transformer potential induced in armature windings in quadrature-axis armature pulsating magnetic field for: (3) Let f be the quadrature-axis armature pulsating magnetic flux, f be the power supply frequency, and f be the transformer potential induced in the excitation winding by the direct-axis pulsating magnetic field. for: (4) W f The number of turns in the excitation winding is given. Due to the position of the brushes and / or the armature winding's connection to the commutator segment deviating from the geometric centerline by an angle β, a direct-axis pulsating magnetic field generates a transformer potential in the armature winding. for: (5) This is the resistance voltage drop between the armature and pole windings. The leakage reactance voltage drop between the armature and pole windings. This refers to the brush voltage drop.

[0020] The phasor diagram corresponding to the voltage balance equation is as follows: Figure 7 As shown, where θ is the current I leading the magnetic flux. The phase angle is determined by the iron loss p. Fe and copper loss p in commutation elements Kcu The effect is generally small. ψ is the power factor angle of current lagging behind voltage, which is very small.

[0021] Because the stator excitation windings of a series-wound motor also need to be connected in series, methods such as... Figure 8-9 The wiring configuration is shown. This is because if the magnetic pole excitation windings are connected in parallel, there are at least two serious hidden dangers: a) Due to factors such as materials, structure and process, it is not possible to guarantee that the impedance of each parallel branch is consistent. This results in unequal currents flowing into each pole, leading to unequal magnetomotive forces generated by the excitation windings of each pole, which degrades the performance of the motor.

[0022] b) If a parallel excitation branch experiences an open circuit fault, the magnetomotive force of that pole will immediately disappear, the motor's magnetic field will immediately become unbalanced, and the motor will be quickly damaged, resulting in waste and even danger.

[0023] From the voltage balance equation and its corresponding phasor diagram, we can see that: 1. Among the various electromotive forces that balance the external voltage inside a series motor, the armature rotational electromotive force E accounts for the largest proportion, plays a major role in balancing the power supply voltage, and is also the main component of energy transfer and conversion.

[0024] 2. According to equation (2), if the armature uses lap winding, the number of parallel branch pairs (a=p) and the total number of conductors N in the armature are proportional to the number of stator pole pairs p. That is to say, the number of conductors in series in each branch (N / (2a)=N / (2p)) remains basically unchanged because it needs to balance the external voltage. The more pole pairs there are, the more total conductors N there are, and the thinner the wire diameter is when the same current passes through. However, more turns and a thinner wire diameter consume production time, have a high defect rate, and are not conducive to production.

[0025] 3. When the armature is a lap winding, with the same number of armature slots, the number of slots allocated to each parallel branch is inversely proportional to the number of pole pairs, while the number of conductors Ws per slot is directly proportional to the number of pole pairs p. In other words, the more poles there are, the more the number of series conductors (N / 2p) in each branch needs to remain essentially constant to maintain the critical parameter E. The total number of conductors N in the armature will then increase proportionally with the number of pole pairs, and the number of conductors Ws per slot will also increase proportionally. If dummy slots are not used, the number of turns Wk of the commutation element will also increase proportionally. This will be discussed later; this is the main reason that directly worsens motor commutation.

[0026] For commutation of series motors, the larger the commutation potential, the more unfavorable it is for commutation.

[0027] 1. The reactance and electromotive force e of the commutation element r (6) Among them, W s The number of conductors per slot in the armature. W s =N / z (7) z is the number of armature slots, L is the armature length, determined by the main performance of the motor, λ is the equivalent ratio permeability, composed of slot shape, tooth tip and end ratio permeability, and is a constant for the motor. a For the average commutation current, T k The commutation period of the commutating element is related to the rotational speed, commutator outer diameter, brush width, and the number of commutator segments K.

[0028] In addition, reducing reactance potential also requires (1) To reduce the mutual inductance potential generated by parallel components in the same slot during commutation, the armature needs to have more slots. If there are no virtual slots, there will be no mutual inductance potential of parallel components in the same slot. However, too many slots will reduce the effective slot area, which will affect the main performance of the motor and is not allowed by the manufacturing process. Alternatively, if there are a small number of virtual slots and each component has a small number of turns, the mutual inductance potential in the same slot will also decrease.

[0029] (2) To reduce the mutual inductance between the upper and lower layers of components in the same slot, short-pitch windings can be used.

[0030] 2. Rotational electric potential (1) When the brush is on the geometric center line, the commutation element and the quadrature axis armature react magnetic flux linkage (8) Where v2 is the linear velocity, which is related to the rotational speed; A is the linear load. D2 is the outer diameter of the armature.

[0031] (2) When the brush is not on the geometric center line, it is necessary to commutate in advance as much as possible to counteract the reactance potential and rotational potential.

[0032] 3. Transformer potential e of commutation element Kt (9) The transformer potential of the commutation element has two very undesirable characteristics: firstly, its value is relatively large, exceeding the reactance potential e mentioned above. r and rotating electric potential e a It is much larger. Secondly, its phase is perpendicular to the two mentioned above, meaning that this potential cannot be eliminated by methods such as brush removal, which is one of the important reasons for the deterioration of commutation in AC series motors.

[0033] According to the aforementioned commutation theory potential equation, the potential that worsens motor commutation is directly proportional to the number of turns or the square of the number of turns in the commutation element. In other words, to improve commutation, the primary task is to minimize the number of conductors W per slot. s This reduces the number of conductors W in the commutation element. k This significantly reduces the commutation potential and improves commutation.

[0034] It can be seen that: 1. A pair-pole series motor has only one pair of parallel branches with a=p=1 (two branches). Therefore, each branch has the most slots for the series conductors, fewer conductors per slot, fewer conductors participating in commutation, and smaller potentials that are unfavorable to commutation. Therefore, for motors around 120V, imaginary numbers are not needed to solve the commutation problem. This is the case for common 12-slot and 16-slot pair-pole motors, where each series branch has 6 and 8 slots respectively. If the applied voltage is around 220V, by using an appropriate imaginary slot number u=2, the number of commutation conductors is reduced, thereby reducing the commutation potential and solving the motor commutation problem. For example, a common 12-slot armature motor has 24 commutator plates, and a 16-slot armature motor has 32 plates, so each series branch has 12 and 16 elements respectively. The more elements obtained, the more the number of turns per element decreases proportionally when the total number of series conductors in each series branch remains unchanged, resulting in a sharp drop in potentials unfavorable to commutation, thus easily solving the commutation problem.

[0035] 2. For multi-pole series motors, the increased number of pole pairs and lap windings, compared to single-pole series motors, directly contradicts the goal of improving commutation. As the number of pole pairs increases, the commutation potential rises sharply, severely deteriorating commutation and driving up material and manufacturing costs to improve it. Common four-pole motors, while increasing the number of armature rotor slots, also require increasing the commutator's outer diameter and number of plates. For example, a 220V four-pole motor with 24 slots and 36 plates has a total of 36 components. However, each series branch only receives 36 / 4 = 9 components, which is worse than a single-pole motor with 12 slots and 24 plates (each branch receives 24 / 2 = 12 components). Meanwhile, the outer diameter of the commutator is increased to 35mm, which is much larger than that of commutators with an outer diameter of about 25mm. In addition, the number of parallel branches is large, the armature winding wire diameter becomes thinner rapidly, the number of winding turns is large and the hooking speed is slow during production, the defect rate is high, etc., which increases the additional material and process costs.

[0036] In summary, multi-pole (commonly four-pole) and lap-wound series excitation motors on the market have serious defects and significant drawbacks.

[0037] II. Technical Solution of the Invention This invention proposes a multi-pole, wave-wound series-wound motor for applications in food processing and small kitchen appliances. The multi-pole design is not limited to the two-pole motors currently found on the market; the number of pole pairs can be determined through electromagnetic calculations, based on the applicable application, to maximize the effective volume and capacity of the motor. It can have two, three, or more pole pairs.

[0038] Addressing the numerous drawbacks of existing multi-pole and lap winding solutions on the market, the key to this invention lies in combining the stator multi-pole and armature windings with wave windings, thereby easily solving the commutation problem of multi-pole motors as easily as a single-pole series motor, thus achieving the goal of significantly increasing the effective volume of the motor and expanding its capacity.

[0039] Specifically, the multi-pole, wave-winding series-wound motor of the present invention includes: a stator and a rotor. The stator is provided with multiple excitation windings, and the rotor is provided with an armature winding. The excitation windings and the armature windings are connected in series. The armature windings are wave windings, and the number of pole pairs p of the stator is ≥ 2.

[0040] The windings are divided into single-wave windings and complex-wave windings. Since this involves low-power food processing and small kitchen appliances, single-wave windings may meet the needs of 95% of products in this field. Complex-wave windings can increase machine capacity, such as in large commercial food processors that can handle multiple people at once. Their characteristics can be derived from those of single-wave windings, and will not be elaborated further here.

[0041] 1. Wave winding style The wave winding pattern is as follows Figure 10 The shape is similar to a wave. The schematic diagram of a multi-pole wave winding is similar in appearance to that of a multi-pole lap winding, but the armature winding is fundamentally different. This invention provides a four-pole, 25-slot single-wave winding, the circuit diagram of which is shown below. Figure 11 As shown, the corresponding winding unfolding diagram is as follows: Figure 12 As shown.

[0042] 2. Functional characteristics of single-wave windings Combined with appendix Figure 10-12 Based on relevant theories, its characteristics can be summarized as follows: (1) Single-wave windings are generally suitable for odd-slot armatures.

[0043] (2) The commutation pitch of a single-wave winding is close to, but not equal to, the pitch of a pair of poles.

[0044] (3) The potential directions of the elements on the same polarity side are the same, forming a branch in series. The magnetic field has only N and S poles. No matter how many pairs of poles p are used, a single-wave winding has only two parallel branches, that is, the number of parallel branches a=1, which is exactly the same as a single-pole series motor. This also shows that when the number of armature slots of a multi-pole series motor is close, the number of series turns per slot or per element of the wave winding is reduced by a factor of two compared to the lap winding. Thus, according to the commutation potential equations, the commutation potential also decreases sharply, thereby solving the commutation problem of multi-pole series motors.

[0045] (4) Under the condition of satisfying the working and commutation performance, the performance of the motor remains unchanged by removing any adjacent pair of carbon brushes. That is, regardless of the number of pole pairs of the motor, if wave winding is used, the minimum number of brushes can be only 2, provided that the conduction or commutation function is satisfied. In some cases, this can be used to simplify the motor brush holder structure and save material and process costs.

[0046] The key difference between the wave winding of this invention and the commonly used lap winding in the prior art is that in equation (2), the wave winding directly sets a=1, which means that with a certain number of winding elements, the more elements connected in series in each branch, the more armature slots are allocated. This is the same as the case of a single-pole motor (i.e., the number of parallel branches does not increase with the number of pole pairs), the number of conductors per slot is reduced, the number of turns of the commutation element is reduced, and the potentials that are not conducive to commutation are also reduced sharply, so that the commutation problem of the motor can be easily solved. At the same time, the wave winding also takes into account the advantages of multi-pole magnetic circuit and short circuit, which not only increases the effective volume of the motor and expands the motor capacity, but also saves material and process costs compared with multi-pole and lap winding motors, and greatly improves production efficiency.

[0047] The present invention also provides a food processing device, including a main unit and a drive motor disposed in the main unit, wherein the drive motor adopts the above-mentioned multi-pole, wave winding series excitation motor.

[0048] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A multi-pole, wave-wound series-excited motor for food processing and small kitchen appliances, comprising: The stator and rotor are provided, wherein the stator is provided with a plurality of excitation windings and the rotor is provided with an armature winding, the excitation windings and the armature windings are connected in series, characterized in that the armature windings are wave windings and the number of magnetic pole pairs p of the stator is ≥2.

2. A food processing device, comprising a main unit and a drive motor disposed in the main unit, characterized in that, The drive motor is the multi-pole, wave-winding series excitation motor as described in claim 1.

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