200924347 九、發明說明： 【發明所屬之技術領域】 本發明係在提供一種利用後充磁法製作永磁無刷馬達 之°又冲方法與流程，特別是指先將馬達完成組裝（包含尚未 充磁之磁鐵）再利用定子線圈通入瞬間大電流來對磁鐵進 行充磁，並可藉调變充磁瞬間之電流，即可產生出不同特 性的馬達，由本發明之技術可獲得更大型化及高效能的永 磁馬達。 【先前技術】 按’傳統運用於較大型或大功率的馬達，通常會使用 感應馬達’但因感應馬達一般有密度較低、It積較大、效 率較低以及控制較困難等缺點，近來遂有高功率密度以及 高效率之永磁式無刷馬達來取代感應馬達。然，永磁式馬 達，尤其是大功率永磁馬達，若使用稀土類(如敍_， NdFeB)磁石，由於其磁力強，導致製程組裝相當不易。一 般傳統製程為先將磁鐵行充磁後，再置入轉子，之後再將 轉子與定子進行對應組配。是以，永久磁石之強磁性極易 吸附鐵屑、細小零件....等雜物’且裝配不易，而造成製程 處理上之困難，並增加成本，甚至可能因所吸附雜物造成 馬達運轉異常、故障等意外狀況。對此問題，雖有先前討 論提出先將未充磁之磁石置入轉子内，再以充礙細轉子 200924347 進行充磁，之後再組裝至定子；然而，此法仍存有具強磁 性之轉子與定子，於組裝上之困難不易克服。因此，大型 永磁無刷馬達之製程，較適合採用完全組裝後，再利用馬 達本身定子線騎電所纽之強磁場鋪_磁鐵充磁，此亦 為本發明所稱之「後充磁法」。然而，傳統先充磁後組裝之 永磁馬達料枝與雜’已不再完全適麟後充磁法之 永磁馬達。 有鑑於此’本發明人始進行研究，以期_現有充磁 技術之困境，因此首先發明出本發明。 【發明内容】 本發明之後充磁技術主要是將馬達組褒之後，利用定 子上之賴’通過_大電流，對磁峨行充磁之馬達設 計及後充磁技術。 後馬達的特性 本發明内容主要有兩大部分，第一部分為，本發明之 後充磁無刷馬達相設計流程；第二部分為，馬達…十— 成後，使用後充磁時，透過電流之調節，來達到不同 = 丹丫’弟一邵分 知兴尺寸的不同，所對 應之充磁糕亦會不同，又充磁·_充 限制(一般為1500V至40〇〇v不 的 設計上會產衫__轉。本發奴寸的初始 ^月利用幾何形狀與磁 200924347 場之物理現象進行數學推導，將充磁所需之電流以馬達尺 寸參數表示之。首先’透過預期的額定功率、轉子功率实 度與反電動勢常數(Back-EMF constant)，計算出馬達轉子半 徑參數r〇 (轉子含磁鐡的外徑）以及n (線圈阻數）兩者之 間的關係，其參數定義如第一及一 A圖所示；第一、一 a 圖所揭係以4極18槽為例之無刷馬刷結構簡易示意圖，其 中馬達1中心設轉子11，轉子11外圍設4極磁鐡12，磁 鐵12外部即為定子13，於定子13之内側等距設有18個槽 130，該等槽130係供組裝線圈，而於轉子u圓心至磁鐡 12外徑即為，轉子η圓心至定子13之槽13G外徑設為 R〇。經推導rG與N兩者之關係如下式所示。 ,rj πΚεΏρ。醫 {Ax power xBgNc〇uj°.....................................〇 額定功率 1/2峰對峰反電動勢常數 ^ power - 轉子功率密度 ‘=每相線圈組數(即每相線圈是由U繞於齒上之子線圈，串聯 而成） 氣隙磁通密度(Tesla) 隨著酿增加，所需要的氣隙磁通密度也隨之下降，如第二 圖所示，其為參第-圖所示之4極18槽無刷馬達進行實際計算之 200924347 範例；圖中近下方之細實線為09Tesla(設計參考值，可依照不同 需求而制定）之參考線，該顆馬達經設計需09Telsa之氣隙磁通 密度，故由圖可選擇19匝（即小圈點與細實線之交叉點）。 透過(式1)設計出N (線圈匝數）後，隨即考慮佔槽率之限制。 若給予特定佔槽率(sl0t_flU factor)以及反電動勢常數，输心之間 的關係曲線可關第三@之虛線表示；經推導，被&之關係曲 線如下式所示。 R〇 = _ KEDpowerNsr〇 、2 V ^coil^SF^s^current^g .............................. 2) 其中， Μ =槽數。 ^二1/2峰對峰反電動勢常數。 ^ power =轉子功率密度。 D Ci/rmj，=額定導線電流密度(A/mm2)。 形狀係數(介於〇〜1之間）。 尸每相線圈組數(即每相線圈是由 組繞於齒上之子 線圈，串聯而成）。 佔槽率。 石g—氣隙磁通密度(Tesla)。 由於該曲線無法完全決定確切之設計點(Designpoint)，也就 疋無法决疋所设計馬達之r〇與R〇，因此必須有另一組充磁限制曲 200924347 線與此曲線之父點方能求得；該曲線之方程式如下 / -4π·Β〇..\ K+r〇 . n sin f \ π 2 + ^ Ν·μ0 ]j 2 h c〇sUJ-〜 其中， (式3) -磁鐵所需之充磁磁通密度(Tesia)。 A =真空導磁係數。 磁鐵極數。200924347 IX. Description of the Invention: [Technical Field] The present invention provides a method and a process for making a permanent magnet brushless motor by post-magnetization, in particular, to complete the assembly of the motor (including not yet magnetizing) The magnet) re-magnetizes the magnet by using a large current in the stator coil, and can generate a motor with different characteristics by adjusting the current of the magnetization moment, and the technology of the present invention can be made larger and more efficient. A permanent magnet motor. [Prior Art] According to the 'traditional application to larger or high-power motors, induction motors are usually used'. However, induction motors generally have disadvantages such as low density, large It product, low efficiency, and difficult control. Recently, 遂A permanent magnet brushless motor with high power density and high efficiency replaces the induction motor. However, permanent magnet motors, especially high-power permanent magnet motors, if rare earths (such as NdFeB) magnets are used, process assembly is quite difficult due to their strong magnetic force. In the conventional process, the magnet row is first magnetized, then placed in the rotor, and then the rotor and the stator are matched. Therefore, the strong magnetism of the permanent magnet is very easy to adsorb iron scraps, small parts, etc. and the assembly is not easy, which causes difficulty in the process, increases the cost, and may even cause the motor to operate due to the adsorbed debris. Unexpected conditions such as abnormalities and malfunctions. For this problem, although the previous discussion proposed that the unmagnetized magnet is placed in the rotor, and then magnetized by the fine rotor 200924347, and then assembled to the stator; however, this method still has a ferromagnetic rotor. With the stator, the difficulty in assembly is not easy to overcome. Therefore, the process of the large permanent magnet brushless motor is more suitable for the complete assembly, and then the magnet is magnetized by the strong magnetic field of the stator line of the motor itself, which is also referred to as the "post-magnetization method" of the present invention. "." However, the conventional permanent magnet motor assembly and the permanent magnet motor are no longer fully magnetized by the permanent magnet motor. In view of the fact that the present inventors conducted research to date, in view of the predicament of the existing magnetization technique, the present invention was first invented. SUMMARY OF THE INVENTION The magnetization technique of the present invention is mainly to design a motor and a post-magnetization technique for magnetizing a magnetic cymbal after the motor is assembled by using a large current on the stator. Characteristics of the rear motor There are two main parts of the present invention. The first part is the design flow of the magnetized brushless motor phase after the present invention; the second part is the motor... after the tenth, after the magnetization after use, the current is transmitted. Adjustment, to achieve different = Tanjung 'di brother, one of the Shaoxing Zhixing size difference, the corresponding magnetic cake will also be different, and magnetization · _ charge limit (generally 1500V to 40 〇〇 v not design will The shirt is __ turn. The initial month of the haircut is mathematically derived using the geometry and the physical phenomenon of the magnetic field 200924347, and the current required for magnetization is expressed by the motor size parameter. First, 'through the expected power rating, The rotor power solidity and the back-EMF constant calculate the relationship between the motor rotor radius parameter r〇 (the outer diameter of the rotor with magnetic enthalpy) and n (the number of coil resistances). The first and first diagrams show a simple schematic diagram of a brushless horse brush structure with a 4-pole 18-slot as an example. The motor 1 is provided with a rotor 11 at the center and a 4-pole magnetic pole at the periphery of the rotor 11. 12, the outer part of the magnet 12 is the stator 13 18 slots 130 are disposed equidistantly from the inner side of the stator 13. The slots 130 are for assembling the coils, and the outer diameter of the rotor u to the outer diameter of the magnetic coil 12 is the outer diameter of the slot δ 13G of the center of the rotor η to the stator 13 is set to R〇. The relationship between rG and N is derived as shown in the following equation: rj πΚεΏρ. Doctor {Ax power xBgNc〇uj°..................... ................〇 rated power 1/2 peak-to-peak counter electromotive force constant ^ power - rotor power density '= number of coils per phase (ie, each phase coil is wound by U The sub-coils on the teeth are connected in series.) The air gap flux density (Tesla) decreases with the increase of the air gap flux density. As shown in the second figure, it is the reference map. The example shows the 200924347 example of the actual calculation of the 4-pole 18-slot brushless motor; the thin solid line in the lower part of the figure is the reference line of 09Tesla (design reference value, which can be made according to different needs). The motor is designed to be 09Telsa. Air gap flux density, so you can choose 19匝 from the graph (that is, the intersection of small circle and thin solid line). After designing N (coil turns) by (Formula 1), consider the slot ratio limit. Give special Taking the slot ratio (sl0t_flU factor) and the back electromotive force constant, the relationship between the heart and the heart can be represented by the dotted line of the third @; after derivation, the relationship curve of & is as follows: R〇= _ KEDpowerNsr〇, 2 V ^coil^SF^s^current^g ........................ 2) where Μ = number of slots. ^ Two 1/2 peak-to-peak counter electromotive force constant. ^ power = rotor power density. D Ci/rmj, = rated wire current density (A/mm2). Shape factor (between 〇~1). The number of coils per phase of the corpse (ie, the coils of each phase are made up of a group of coils wound around the teeth, connected in series). Occupy slot rate. Stone g—air gap flux density (Tesla). Since the curve cannot completely determine the exact design point (Designpoint), it is impossible to determine the r〇 and R〇 of the designed motor. Therefore, there must be another set of magnetization limiter 200924347 line and the parent point of this curve. Can be obtained; the equation of the curve is as follows / -4π·Β〇..\ K+r〇. n sin f \ π 2 + ^ Ν·μ0 ]j 2 hc〇sUJ-~ where, (Formula 3) - Magnet The required magnetizing magnetic flux density (Tesia). A = vacuum permeability. The number of poles in the magnet.
々如前所述’由於佔槽率之限制，可繪製出r。與〜之關係曲線， 如第二圖虛線所示；另外，再透過(式3)可另外綠製出，不同充 磁電流下，讀R。之關係曲線；如第三圖實線所則虛線與實 線之交叉點，即為該馬達之設計點。透過本發明之推導，可順利 預測馬達在不同尺稍規格下，所需要之魅魏，_進行細 部尺寸設計。 由於所設計馬達必須同時符合可施行後充磁，並於充磁後可 正常運轉之條件’耻另外—減線必須域磁電流所決定。故 本發明另在提供-種設計時需考慮佔槽率、隨以及線徑等參 數，且經设計之馬達須極接近需求規格以確保後充磁的可行性， 並能將後充雜序及馬達需求-併考慮之設雜序。基本尺寸設 計完成後，即進入細部尺寸之設計流程。 馬達之細部尺寸計算(磁路設計），方法與一般傳統馬達設計 方式相同。計算集中係數係為必要之程序，又為能計得馬達内部 在充磁瞬間的磁場強度(magnetic intensity)，須配合計算磁鐵寬 200924347 度、計算氣隙、磁鐵長度三者係數，以提供幾何關係尺寸，始得 以計算之。 第二部分，由於本發明之後充磁技術，因充磁電流之瞬間最々 As mentioned above, r can be drawn due to the limitation of slot rate. The relationship with ~, as shown by the dotted line in the second figure; in addition, through the (Formula 3) can be additionally green, read R under different magnetizing currents. The relationship curve; if the solid line in the third figure is the intersection of the dotted line and the solid line, it is the design point of the motor. Through the derivation of the present invention, it is possible to smoothly predict the required size of the motor in different sizes and specifications. Since the designed motor must meet the conditions that can be post-energized and can be operated normally after magnetization, the condition of shame must be determined by the field magnet current. Therefore, the present invention also needs to take into account the parameters such as the slot ratio, the wire diameter, and the like, and the designed motor must be close to the required specification to ensure the feasibility of post magnetization, and can be post-filled. And motor demand - and consider the order. After the basic size design is completed, the design flow of the detailed dimensions is entered. The motor's detailed size calculation (magnetic circuit design) is the same as the conventional motor design. Calculating the concentration factor is a necessary procedure, and it is also able to calculate the magnetic intensity at the moment of magnetization inside the motor. It must be calculated by calculating the magnet width of 200924347 degrees, calculating the air gap and magnet length to provide geometric relationship. The size is calculated from the beginning. In the second part, due to the magnetization technology after the present invention, the moment of magnetizing current is the most
大值(Peakvalue)為主要關鍵因素；被充磁對和表面黏著型，SPM 以及内藏磁鐵型，ΙΡΜ馬達)在飽和以前，隨著充磁電流愈大，其 反電動勢常數(BaCk-EMFC0nstant)也將愈高，如第四圖所示，呈 現指數型增加(非雜增加）；但到達飽和點之後，即使充磁電流 增加，亦無法增加其反賴勢錄，即為獨充磁電流下，所= 到之反電動勢崎圖。該圖係為4極18槽之馬達經本發明人實 際測試之實驗絲’由圖式顯示，本發明所_後充磁之方式， 極為接近完全飽合(虛線位置），並由上升曲線確定，可達到調制 之功能。 本發月利用後充磁製作馬達時’運用調節馬達反電動勢常數 之方法，以改變馬達再操作點時之特性；係使馬達能夠有不同的 輸出轉速與轉矩比例(相當於減速比之公用）。 本發明之後充磁法主要是在馬達組裝後，利用定子線圈通過 瞬間大電流，以將轉子磁鐵充磁之方法；係經由後充磁時，轉子 磁鐵飽和度之不同，可以調節其反電動勢；可不需修改繞組或者 馬達之幾何形狀，僅須改變不同的充磁瞬間電流大小後，即可得 到不同的馬達反電動勢。 本發明方法係利用後充磁技術來組裝含有稀土類磁鐵馬達， 200924347 捕定的雜辦之下，提升规之效率，财設計上可降低銅 線之規格以節省成本。 …本㈣之主要特徵，其主要係先預設馬達制之败功率及 額定轉子功率时後，再輯馬達轉子半雜隨⑼，透過計 异充磁電流、舣賊’饋充断行後，再計狀子之外半徑， 否則重新③計馬達轉子半徑；初步尺寸完祕，咖始計算集中 係數、轉麵寬度、計算氣隙、顧長度等細部參數。 【實施方式】 本發明所提供朝於表轉著型(SPM)與喊磁鐵型 (IPM)之無刷馬達之後充磁技術’請配合參閱第五圖所示， 其實施流程為： (1·)依據馬達f求與規格，首辆設馬達使狀額定功率及 額定轉子功率密度； (2.)其次，依所欲得之反電動勢並參考式⑴之公式，緣製馬 達尺寸參射N(賴數)與之(轉子半彳調係曲線； (3·)依式(2)之公式計算受佔槽率限制下定子槽半徑r〇之長 度； ~ (4·)檢麵磁電流、額定電流；因不_充磁電流會產生不 同的限制曲線’故依前述，參式⑶計算出適當之充磁電 流值； (.)判斷其充磁可行性’僻為可行則再轉子半徑^、外半 200924347 輕R〇與反電動勢常數進行馬達細部結構設計；否則再回 步驟1重新設計馬達轉子半徑與阻數； (6·)參一般通用方式計算集中係數、計算磁鐵寬度、計算氣 隙、磁鐵長度·’集中係數為傳統馬達設計時之參考係 數，故於本發明之後充磁馬達之的設計上乃為必要之程 序；另外，磁鐵寬度、計算氣隙、磁鐵長度三者係數， 其一為提供幾何關係尺寸，使馬達内部的磁場強度 (magnetic intensity)在充磁瞬間得以計算之；其二則為此 二參數影響馬達之反電動勢常數，與一開始之規格制定 有關，為必要計算之過程； (7·)進行數值合理與否之判斷，倘不合理時，則重新給定pc 值再重回步驟(2.) ’倘若合理則完成細部參數設計；由於 磁鐵之厚度是否合理，取決於磁鐵製造困難度與成本考 量，而氣隙長度一般設計約在0.4〜1.5麵之間，依此經 驗數據來判斷是否合理；另，pc值為控制磁鐵操作點 之磁路上重要設計依據，通常為4〜6之間(例如鈥鐵硼 磁鐵）’依磁鐵不同而不同，提高Pc值，磁鐵可承受較 大之磁場，但相對應之馬達尺寸將會改變(合理與否，將 取決於設計馬達之大小，是否符合成本），此處為疊代法 找出適當之Pc值。 經由以上說明，可見本發明所具有之獨特創作與優異 12 200924347 進步性： /·針對後充磁技術之實施’現有電流試驗技術之運用， 其係運用已組成之馬達結構，嘗試輪付同電流，試驗、 、】出敢適且之充磁電流，但，須试驗(犧牲)若干成品後，始 可得出較佳實施電流，且須耗費測紅時，極不經濟，而 本發明恰可改善此一缺失。 2. 傳統馬達製造，不同線圈，轉子、槽極、匝數等不同， 須開設不同製作模具，成本高，且又有充磁技術上之缺失 與困擾，本發明可突破此一困境。 3. 本發明可依不同馬達功率，線圈設計，亦考慮到佔槽 率之重要參數(佔槽率太高，會造成試驗品試作上之困難）。 之後，再充磁’即可形成馬達以供制，_犠牲試驗品， 亦無開模之尚成本支出。 4. 本發明可藉由控制充磁電流進行馬達特性之調整，故 可減省生產線之開設（無須不同規格特性之馬達，就另外發 展生產'，泉。即生產線上可翻），僅須運㈣充磁電流即可 生產不同特性之馬達。 &、上所述’本發财法確實已能制所麵之使用目 的及力放故本發明誠已符合發明專利之_請要件，妥依 法提出發财歡申請，料惠料查，並早日賜准專利， 則實感德馨。 200924347 【圖式簡單說明】 第一圖所示為馬達結構示意圖。 第一 A圖所示係為r〇、R〇之尺寸參數標示圖。 第二圖所示為在特定轉子半徑下，匝數與氣隙磁通密度之 關係圖。 第三圖所示為不同充磁電流下之限制曲線(實線)與佔槽率 之限制曲線圖。 第四圖為不同充磁電流下所產生之反電動勢峰值圖。 第五圖所示為本發明流程圖。 【主要元件符號說明】 1 馬達 11 轉子 12磁鐵 13 定子 130槽 14Peak value is the main key factor; the magnetization pair and surface adhesion type, SPM and built-in magnet type, ΙΡΜ motor) before saturation, the larger the magnetizing current, the back electromotive force constant (BaCk-EMFC0nstant) It will also be higher, as shown in the fourth figure, showing an exponential increase (non-mix increase); but after reaching the saturation point, even if the magnetizing current increases, it is impossible to increase its reciprocal recording, that is, under the single magnetizing current , = = to the anti-electromotive force map. The figure is a 4-pole 18-slot motor. The experimental wire actually tested by the inventors' is shown by the drawing. The method of post-magnetization of the present invention is very close to full saturation (dashed line position), and is determined by the rising curve. The function of modulation can be achieved. This month, when using the magnetization to make the motor, the method of adjusting the motor back electromotive force constant is used to change the characteristics of the motor re-operation point; the motor can have different output speed and torque ratio (corresponding to the common speed reduction ratio) ). The magnetization method after the invention is mainly a method of magnetizing a rotor magnet by using a stator coil through an instantaneous large current after the motor is assembled; and the back electromotive force can be adjusted by the difference in saturation of the rotor magnet after magnetization; It is not necessary to modify the geometry of the winding or the motor, and only after changing the magnitude of the different currents of the magnetization, different motor back electromotive forces can be obtained. The method of the invention utilizes post-magnetization technology to assemble a motor containing a rare earth magnet, and the efficiency of the lifting gauge can be reduced under the miscellaneous regulations of 200924347, and the design of the copper wire can be reduced to save costs. ... The main characteristics of this (4), mainly after presetting the power loss of the motor system and the rated rotor power, then re-recording the motor rotor semi-mixed with (9), after counting the different magnetizing current, the thief's feeding and breaking, then The radius outside the meter is used, otherwise the radius of the motor rotor is re-calculated; the initial size is complete, and the details of the concentration factor, the width of the plane, the calculation of the air gap, and the length of the gauge are calculated. [Embodiment] The present invention provides a magnetization technology for a brushless motor (SPM) and a shim magnet (IPM). Please refer to the fifth figure. The implementation process is as follows: (1· According to the motor f and the specifications, the first set motor rated power and rated rotor power density; (2.) Secondly, according to the desired counter electromotive force and reference formula (1), the edge motor size is N ( Lap number) (the rotor half-turn adjustment curve; (3·) according to the formula of formula (2) to calculate the length of the stator slot radius r〇 under the slot ratio limit; ~ (4·) check surface magnetic current, rated Current; because no magnetizing current will produce different limiting curves', according to the above, the formula (3) calculates the appropriate magnetizing current value; (.) judges the magnetization feasibility of the re-rotor radius ^, The outer half 200924347 light R〇 and back electromotive force constant for the motor detailed structure design; otherwise, return to step 1 to redesign the motor rotor radius and resistance; (6·) refer to the general general method to calculate the concentration factor, calculate the magnet width, calculate the air gap, Magnet length · 'concentration factor is the reference system for traditional motor design Therefore, the design of the magnetizing motor after the present invention is a necessary procedure; in addition, the three factors of the magnet width, the calculated air gap, and the magnet length, one of which is to provide a geometric relationship to the magnetic field strength inside the motor ( The magnetic intensity is calculated at the moment of magnetization; the second is that the two parameters affect the back electromotive force constant of the motor, which is related to the initial specification and is the process of necessary calculation; (7·) the judgment of whether the value is reasonable or not If it is unreasonable, re-given the pc value and then return to step (2.) 'If it is reasonable, complete the detailed parameter design; because the thickness of the magnet is reasonable, it depends on the difficulty of manufacturing the magnet and the cost consideration, and the length of the air gap The general design is between 0.4 and 1.5 faces, and it is judged whether it is reasonable according to the empirical data. In addition, the pc value is an important design basis for controlling the magnetic circuit operating point of the magnet, usually between 4 and 6 (for example, neodymium iron boron magnet). 'Depending on the magnet, increasing the Pc value, the magnet can withstand a large magnetic field, but the corresponding motor size will change (reasonable or not, it will depend on the design of the motor) Whether it is cost-effective), here is the iterative method to find the appropriate Pc value. Through the above description, the unique creation and excellence of the present invention can be seen 12 200924347 Progressive: /· Implementation of post-magnetization technology 'current current The application of the test technology, which uses the already composed motor structure, attempts to pay the same current, test, and circulate the magnetizing current, but after testing (sacrificing) some finished products, it can be concluded. It is extremely uneconomical to implement current and it is necessary to measure red, and the present invention can improve this deficiency. 2. Traditional motor manufacturing, different coils, rotors, slots, turns, etc., different molds must be opened. The invention has the advantages of high cost and lack of magnetization technology, and the present invention can overcome this dilemma. 3. The invention can be designed according to different motor powers and coils, and also takes into account the important parameters of the slot ratio (which is too high in the slot rate, which may cause difficulty in testing the test product). After that, re-magnetization can form a motor for the production of _ 犠 试验 试验 test, and there is no cost of opening the mold. 4. The invention can adjust the motor characteristics by controlling the magnetizing current, so that the opening of the production line can be reduced (the motor can be developed separately without the motor of different specifications), and the spring can be turned over. (4) Magnetizing current can produce motors with different characteristics. &, the above-mentioned 'this financial method has indeed been able to make the use of the purpose and force to release the invention. The invention has been in line with the invention patent _ request, appropriate to make a wealthy application according to the law, expected to benefit the investigation, and As soon as the patent is granted, it is really sweet. 200924347 [Simple description of the diagram] The first figure shows the schematic diagram of the motor structure. The first A picture shows the size parameter map of r〇 and R〇. The second graph shows the relationship between the number of turns and the air gap flux density at a given rotor radius. The third graph shows the limit curve (solid line) and the slot ratio limit for different magnetizing currents. The fourth graph shows the peak value of the back electromotive force generated under different magnetizing currents. The fifth diagram shows the flow chart of the present invention. [Main component symbol description] 1 Motor 11 Rotor 12 Magnet 13 Stator 130 slot 14