The effect of temperature on torque motor air gap reluctance and permanent magnet polarization magnetomotive force

Transcription

1 International Conference on Avance Electronic Science an Technoloy (AEST 16) The effect of temperature on torque motor air ap reluctance an permanent manet polarization manetomotive force Jiayan Qina Chanchun Li Hao Yan Lei Li an Chan Xue School of Mechanical Electronic an Control Enineerin Beijin Jiaoton University Beijin China Abstract. The temperaturefactor is introuce in moelin proress base on ouble nozzle baffle electro-hyraulic servo valve torque motor. A new temperature moel of air ap reluctance an polarization manetomotive force was propose. An an accurate manetic flux computin metho was euce in orer to provie the basis for the establishment of a new torque motor moel an the servo valve temperature characteristic analysis. Keywors: torque motor; temperature; reluctance; polarization manetomotive force. 1 Introuction Rocket launcher process requires to tolerance the limit hih temperature. Because of the effect of hih temperature as oil temperature of servo hyraulic can rise up to about 15 from the room time urin 8s. The temperature of the servo valve torque motor will rise to close to the oil temperature in a very short time. Therefore the analysis of thermal characteristics at hih temperature is very necessary. In the omestic stuy Qi-xin Xiao propose the qualitative impact of temperature for each hyraulic servo valve element comprisin a torque motor as well as the oil viscosity. Chan-hai Liu conucte electromanetic torque of motor torque an the manetic circuit theoretical euction by Kirchhoff's law an establishe a new moel. Forein scholars Merritt E. H euce an ieal mathematical moel usin air ap reluctance as a startin point[9].an the existin theoretical moels of torque motor usin empirical formula which is lack of temperature factor. In this article reluctance of permanent manet an polarization manetic motive force are put as the startin point the impact of temperature on it is iscusse the oriinal formula is correcte an a theoretical basis for the establishment of a new moel of torque motor is provie at the hih temperature. Parameter calculation of torque motor The role of the torque motor is to convert electrical sinals to mechanical movement. It s compose of permanent manet top yoke bottom yoke armature coil flexure tube an other components. Fiure 1a epicts a torque motor manetic circuit schematic iaram. We can assume that reluctance of manetic material an non-workin air ap is neliible. The torque motor manetic circuit can be represente by equivalent manetic circuit shown in Fiure 1b. a Corresponin author : @bjtu.eu.cn 16. The authors - Publishe by Atlantis Press 13

2 AEST16 When the armature is locate in the meian reluctance of each workin air ap is: R l / A the lenth of each of the air ap when armature is at the meian position; A the area of the 7 manetic pole faces; the permeability of air 4 1 Wb / ma.. l Fiure 1. Torque motor manetic circuit schematic iaram When the armature eviates from the meian position for the isplacement of x reluctance of air ap is: l x x R1 R (1 ) A l l x x R R (1 ) A l (1) Excluin the effect of temperature on the reluctance of the air ap there is: R1 R3 R R4 where R reluctance of air ap 1; reluctance of air ap ;x the isplacement that the armature is 1 R eviates from the meian position. 3 Effect of temperature on the reluctance torque motors The permanent manet of torque motors usually use A1-Ni-Co permanent manet alloy. The materials that flexure tube usually use 3J1 alloy. The materials that top an bottom yoke an armature usually use 1J5 alloy[3].thermal expansion of materials is usually expresse as linear expansion coefficient [5].The material an expansion coefficient of each torque motor part is as follows: Table 1. The material an expansion coefficient of each torque motor part Material Part name /1 ( C) name Permanent manets A1-Ni-Co 11 The top an bottom yoke 1J5 9. armature 1J5 9. Flexure tube 3J When the armature of torque motors is locate in the meian since thermal expansion phenomenon of permanent manet the top an bottom yoke the armature an flexure tube the lenth of the air ap will chane thus affect the manetic resistance. At room temperature ( ) the size of the torque motor components is as shown in Fi.. Fiure.The size of each torque motor component At room temperature the lenth of the up air ap an the own air ap is: l L L l L L () Durin the process that the temperature rises from room temperature to 15 the parts expan 14

3 AEST16 with fixation surface shown in the fiure as a reference plane The formula of the coefficient of linear expansion is l l T.There are: ' 1 L L 1 ' T L L 1 ' T L L 1 T L 1 T L 1 T L L T ' (3) Amon these formulas 1 is linear expansion coefficient of the top an bottom yoke is linear expansion coefficient of the flexure tube 3 is linear expansion coefficient of the permanent manet. After heate an in liht of Eq. (3) the lenth of air ap is: ' ' ' l L L l K T l L L l K T (4) ' ' ' Amon these equations: K L L L L K L L (5) Put the measure actual size into the above equations an raw curves as follows: Air ap lenth(mm) Up air ap Down air ap Fiure 3.Thecurve that shows relation between air ap an temperature Put Eq.(5) into Eq. (1) is: R l K T x l K T x R A A l KT x l KT x R3 R4 A A (6) 4 Temperature effect on permanent manet polarize manetomotive force Manetic material properties chane as the temperature chanes When the temperature rises the remanence B r an coercive force Hcof har manetic material ecrease It may make chanes in the operatin point[4]. With the manetic steel is manetize when the manetic flux ensity reaches saturation manetic flux ensity it can be consiere that manetic steel has become a permanent manet. In this case stop manetizin but manetic steel is still on the manetizin machine the manetic flux ensity of the permanent manet alon with the B-H characteristic curve rops to B r [6][7]. 15

4 AEST16 Fiure 4.The B-H characteristic curve of the permanent manet Fi.4 epicts the B-H characteristic curve of the permanent manet the followin formula can obtain manetic inuction intensity B an manetic fiel strenth H at the point of maximum manetic enery prouct. B H B H B H 4B H c r c r c r c H B (7) B H Amon these formulas r c r c is a constant relate to the permanent manet. B H Point E is the point of maximum emanetization(reply startin point). Althouh the slope of the line reply is relate to the location of the startin point Eit may take approximately the tanent slope of emanetization curve an the vertical axis intersection point ( FB r )to represent in enineerin. Draw parallel line at point E the intersection of the parallel line an the loa line Is actual workin point of permanent manet.fi.5 shows that: Br Bk Be k tan (1 ) Hc Hc Hk (8) In the actual operatin point of the permanent manet there is followin relationship between the manetic flux throuh the permanent manet an the manetic inuction intensity : Bk / Ak the manetic flux throuh the permanent manet(wb); A k the cross sectional area of the permanent manet( m ); Substitute into the Eq. (9) an arrane to obtain: 1 Be Hk ( Hc ) A k k k lk Be M Hklk lk ( Hc ) A k k k (9) (1) An the manetomotive force of the permanent manet can be expresse as: Be Br M l ( H ) l k c k k k (11) l k the effective lenth of the permanent manet; M manetic motive force for external manetic circuit provie by permanent manet except internal maneto resistance consumption manetomotive force of permanent manet(a) Put Eq. (8) into Eq. (11): 16

5 AEST16 M Hc lk BH r c ( 1) (1) The relationship between resiual manetism ensity an temperature is: B [1 ( T ) ] (1 IL) B r Br rc (13) B r the reversible temperature coefficient of B r ; IL Irreversible loss rate of B ; r Br C the resiual manetism ensity when temperature is. Calculate coercive force: H [1 ( T ) ] (1 IL) H c Br cc (14) Hc C the coercive force when temperature is. The permanent manet material of torque motor analyze in this stuy is Al-Ni-Co permanent manet alloys manetic properties of Al Ni an Co chanes very little with temperature chanes. The temperature coefficient of resiual manetism-.%/ irreversible loss rate is Br Cis 1.7T H 3 c C is 51A/m maximum manetic enery is 5KJ/ m. Substitutin the parameters into the above equations rawn curve of relation between M an temperature as fiure shows: polarization manetomotive force(a) 6.5 x Fiure 5. The curve of relation between ~15 polarization manetomotive force an temperature 5 Experimental results In orer to etermine the feasibility an accuracy of the theory the experiment was carrie on in this paper by usin hih temperature test ri. Servo valve is fixe on the hih temperature test ri. Cover torque motor with transparent shiel. Install beam sensors on the top. The experiment schematic iaram is as follows: A P T B t Laser sensor Thermometer Torque motor Laser beam Main valve core Hih temperature test ri Temperature sensor Fiure 6.The experiment of temperature - air ap It is similar to verify polarize manetic motive force - the temperature curve. Remove the top yoke of torque motor install a manetometer on the position of top yoke. 17

6 AEST16 Air ap lenth(mm) Fiure 7. The curve of relation between air ap an temperature Collate the experimental ata analyze an compare the theoretical curve an experimental curve chane stren of the two curves is consistent. How well is oo. polarization manetomotive force(a) 6.5 x Conclusion It starte with the structure an workin principle of the torque motor an quantitatively analyse the effect of temperature on the air ap reluctance an permanent manet polarize manetomotive force. It euce linear equations an set torque motor of a certain type of servo valve as the research object. It provies the basis for the next step to carry out analysis of thermal characteristics of servo valve.[8][1] Reference 1. YIN Yaobao. Theory an Application Technoloy on Electro-hyraulic Servo Control uner Extreme Conitions.[M].Shanhai: Shanhai Science an Technoloy Press LI Honren. The Hyraulic Control System [M].Beijin: National Defense Inustry Press XIAO Qixin. Temperature Effect on Characteristics of Electro-hyraulic Servo alve [D].Shanhai: School of Mechanical Enineerin TonjiUniversity SHEN Dejun. WANGZhishan. Temperature Zero Drift of The Force Feeback Electro-hyraulic Servo alve [J]. Chinese Hyraulics an Pneumatics YIN Yaobao[1]XIAO Qixin[1]YAN Shimin[].Analysis on the Influence of Temperature on Electro-hyraulic Servo [J].Flui Power Transmission an Control LIU Chanhai. Stuy on moelin an simulation of Two-stae Nozzle Flapper Servo alve with Force Feeback [D].Harbin : Harbin Institute of Technoloy ZHOU Anruo MAYilon CHEN Denmin. Stuy on 1J5 Soft Manetic Alloy Temperature Stability[J].Functional Materials LI Fen MA Chenli WANG Kai. Analysis on Electro-hyraulic Servo alve Fault Mechanism uner the Influence of Temperature [J] MERRITTE. H. Hyraulic Control Systems New York: John Wieley 1967: LI Min WANG Wei. Calculation an Analysis of Temperature Fiel for BrushlessDC Torque M otor [J].MICROMOTORS