GENERATOR FOR ALTERNATIVE POWER ENGINEERING WITH REDUCED STARTING RESISTIVE TORQUE

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1 ENGINEERING FOR RURAL DEVELOPMENT Jelava, GENERATOR FOR ALTERNATIVE POWER ENGINEERING WITH REDUCED STARTING RESISTIVE TORQUE Aleksandrs Gasparjans, Marija Hramcova, Aleksandr Terebkov, Anastasia Zhiravetska Latvian Maritime Academy, Ria Technical University Abstract. Construction of an inductor contactless electrical machine is introduced: a enerator with excitation from permanent manets with the decreased moment of resistance at startin. Contactless disk-type multipolar enerators with excitation from permanent manets are becomin more common in small scale wind and hydropower eneration now. It is known that this type of enerators has characteristic disadvantaes. In particular, these enerators have the effect of manetic freezin. The effect makes the start of rotation of the windwheel and its subsequent acceleration to the rate rpm difficult. To eliminate the effect and to improve the startin characteristics construction of a enerator with variable air ap is suested. Variable air ap size is reulated by a centrifual reulator. For this purpose the part of the manetic circuit of the rotor is a movin element. The air ap δ has its maximum value at a motionless rotor or low rotation anular frequency. Herewith, manetic linkae is minimal and the enerator has an insinificant resistive startin torque. With the increasin of the anular frequency the manetic system of the rotor moves alon the axis of rotation by the force caused by the centrifual reulator. In the result the air ap decreases, the manetic system increases flux linkae and the enerator starts to produce electric enery. At reduction of the anular rotation frequency under the influence of restorin the sprin manetic system of the rotor moves to the oriinal position. The technical-economical effect comes from the decreasin of the resistive torque of the inductor machine shaft, i.e., improvement of the startin characteristics. On the construction of the described enerator the patent of the Latvian republic is obtained in []. Keywords: centrifual reulator, air ap, resistive torque, manetic stream. Introduction A construction of a contact-less inductor electric machine with improved startin and reulation characteristics is suested. Nowadays, the multi-pole contact-less enerators of disk construction with the permanent manet excitation are more applied in small hydro- and wind power enineerin. The enerators of such construction have a disadvantae: an effect of manetic sealin. A construction of a contact-less inductor electric machine with improved startin and reulation characteristics is suested. Nowadays, the multi-pole contact-less enerators of disk construction with the permanent manet excitation are more applied in small hydro- and wind power enineerin. A simple construction, small sizes and low anular velocity ive an opportunity to install them on the same shaft with the turbine without any kind of ear either chain or V-belt ear. The enerators of such construction have also some disadvantaes. Particularly, they have an effect of manetic freezin. This complicates the beinnin of the drivin mechanism rotation and further acceleration to the rated number of turns. For the elimination of this effect and improvement of the startin characteristics a construction of the enerator is suested with a variable air ap the value of which is reulated by means of a centrifual reulator. With this purpose a part of the manetic circuit is made movable. With an unmovable rotor and low anular velocity the air ap is of maximum value. The manetic flux linkae and enerator have an insinificant startin resistive torque. With the increasin of the anular rotatin frequency the manetic system of the rotor is movin alon the rotation axis bein influenced by the force of the centrifual reulator. With this the air ap is decreased, the manetic flux linkae increases and the enerator starts to recuperate electric enery. With the decreasin of the anular velocity under the influence of the return sprin the rotor manetic system returns to the initial state. The centrifual reulator of the air ap value is a constructive part of the rotor manetic circuit of the machine. Discussion The synchronous enerators of the disk-type with permanent manets posses an effect of manetic freezin. With the number of windins equal to that of the poles when the manetic pole oes bypass the core of the coil a jump of the resistive torque takes place on the shaft. In the multipole enerators this jump can be sinificant enouh. One of the methods to reduce the effect of the manetic freezin is decreasin or increasin for - units of the number of coils in comparison with the number of manets []. In the construction [3] the manetic system of the rotor is realised as the 49

2 ENGINEERING FOR RURAL DEVELOPMENT Jelava, pole tips slidin apart in the radial direction. The proposed construction uses the principle of the air ap chanin in the manetic circuit of the machine in accordance with the anular velocity of the shaft. Cinematic scheme of the centrifual reulator of the air ap The cinematic scheme of the centrifual reulator on the basis of J. Watt is demonstrated in Fi.. The left side of the fiure contains the forces diaram, but the riht the cinematic scheme of the reulator. Fi.. Cinematic scheme of the centrifual reulator: l, l lenth of the bar; h, h projection of the bar l onto the rotation axis (the heiht of the weiht lift); L lenth of the bar; h projection of the bar onto the rotation axis (the heiht of the weiht lift); F force of the bar reaction; Φ force of inertia; G ravity force; F counteractin force of the bar reaction; α anle of the bar declination; ω anular rotation frequency; R radius of the weihts rotation; acceleration of ravity; moveable rotor; fixed stator The friction in the joints and the mass of the levels (bars) can be nelected. The mass of the weihts is point. Assume the lenth of the bars l, l equal. Force of inertia Φ is: where m mass of the weihts. If to replace Further G m= and r = l, then we obtain: where acceleration of ravity. Φ = mω R, () G Φ = ω l. () Φ lω tα = =, (3) G 430

3 ENGINEERING FOR RURAL DEVELOPMENT Jelava, Takin into account that t α = expression (3) can be transformed to cosα after the cancellation: where from the heiht of the weihts lift is equal lω = ; cosα lω cosα = ; cosα = (4) l ω h= l cosα. (5) With the unmovable rotor or its low anular frequency of rotation the initial declination anle of the weihts is α, determined by the rotor constructive parameters. This moment corresponds to the position A and the heiht of the weihts lift h with the rotation radius r A. With the increasin of the anular velocity to ω the weihts under the influence of the centrifual force Φ part oin up, and takin the location B with the rotation radius r B and the heiht of the weihts lift h. In addition the clutch oes down alon the rotation axis reducin with it the air ap δ in the manetic circuit of the machine. Let us assume that l = l. In accordance with the previous calculation on the basis of (5): h = l A cosα and correspondinly lb cosα Substitutin the values of сosα from (4) into (6), we obtain: h =. (6) h = and h =. (7) ω ω The value of the air ap δ in the manetic system of the inductor machine is determined as ω ω δ = h h = =, (8) ω ω ω ω From expression (8) it is obvious that the value of the air ap variation δ does not depend on the lenth of the bars l, l and weiht mass m. The lenth of the bars and weiht mass influence the forces of the centrifual reulator. The return sprin 0 (Fi. 3) also plays a role of oscillation damper. Fi. represents the raph of the air ap chanin δ accordin to the anular rotation frequency ω. The anular velocity was chaned from.047 rad s - to 0.47 rad s -. Fi.. Graph of the air ap chanin δ accordin to the anular rotation frequency ω 43

4 ENGINEERING FOR RURAL DEVELOPMENT Jelava, This construction of the enerator with reduced startin resistive torque is patented in the Republic of Latvia []. The invention refers to contact-less electrical machines and could be applied in alternative power enineerin. The purpose of the invention is to decrease the resistive torque of the inductor electric machine at its startup and with low anular frequency of the shaft rotation. Fi. 3. Constructive scheme of the enerator with a reduced startin resistive torque The purpose of the invention is to decrease the resistive torque of the inductor electric machine at its startup and with low anular frequency of the shaft rotation. The inductor electrical machine with a variable air ap and decreased resistive startin torque consists of fixed stator with core and stator windins 3 of rotatin shaft 9 with movin manetic circuit 5 with permanent manets 4, return sprin 0 and centrifual reulator 6, 7, 8 fixed on the shaft 9 and rotatin with it. The distinctive part is characterized with the fact that at low or zero (startin) rotation frequency movin the manetic circuit 5 influenced by the return sprin 0 is at outside riht position on the rotor shaft 9. At the same time the air ap δ has its maximum value. Due to insinificant flux linkae the resistive torque on the shaft 9 is minimal. With the increasin of the anular frequency of the shaft 9 rotation flyweihts 6 start to be influenced by centrifual forces and drift from the shaft 9. Their movin over the lever 7 results in the movin alon the shaft 9 of the rotor 5 to the left, overcomin the force of the return sprin 0. It decreases the air ap δ in the manetic system increasin the flux linkae and value of the produced emf in the coil 3. It results in the increasin of the enerator resistive torque. Selectin the mass of centrifual flyweihts 6, the ratio of the lever 7 arms and riidity of the return sprin 0, it is possible to obtain an optimal relation of the air ap δ value and shaft 9 rotation anular frequency. Therefore, at startup of the shaft 9 the enerator has a low startin resistive torque. The invention could ive benefit in the wind enerator startup process, in the enerators driven from the internal-combustion enines. The technical-economical effect comes from the decreasin of the resistive torque of the inductor machine shaft, i.e., improvement of the startin characteristics [4; 5]. In practice the chanin of the air ap δ in the rane from 0.3 mm to 5 mm, i.e., approximately 6 times, is enouh. Calculation of the manetic circuit of the enerator The preliminary calculations of the enerator parameters accordin to methodoloy [6] proved that for the chanin of the enerator resistive torque within a wide rane the air ap δ should be chaned in a small rane. 43

5 ENGINEERING FOR RURAL DEVELOPMENT Jelava, The mechanical force in the manetic field is expressed as a deviation of the manetic field enery alon the coordinate [7]: where W M enery of the manetic field in the air ap. WM F =, (9) x BHSδ W M =, (0) where B, H induction and intensity of the manetic field in the air ap; S square of the cross-section of the manetic circuit; δ value of the air ap. Then the force accordin to (9) WM BHS B S F = = = δ µ, where µ о manetic constant applyin the full current law. o () H S l S+ H Rl R+ H δ δ = Iw, () where H S, H R, Hδ intensity of the manetic field in the stator, rotor and air ap correspondinly; w number of turns of the stator coil; I current in the stator coil; l lenth of the middle line of the manetic circuit of the stator and rotor correspondinly. Therefore, µ o B ( ) δ = Iw H Sl S H Rl R. (3) δ Substitutin the expression of induction (3) into () we will obtain the formula for the force µ o ( Iw H Sl S H Rl R) F = S. (4) δ The calculations were made accordin to formulas (3) and (4) and the raphs represented (Fi. 4 and Fi. 5). B, T 0.6 B=f(δ) F*, T. F*=f (δ) δ, mm δ, mm Fi. 4. Graph of the induction chanin in the air ap dependin on the value of the air ap δ Fi. 5. Graph of the electromanetic force chanin in the air ap dependin on the value of the air ap δ 433

6 ENGINEERING FOR RURAL DEVELOPMENT Jelava, Conclusions. The model of a enerator with a reduced startin resistive torque is developed.. This model of the enerator can be applied in small wind power enineerin. References. LV patents LV 4495 B /Jānis Greivulis, Aleksandrs Gasparjans, Aleksandrs Terebkovs // Latvijas Republikas Patentu Valde, г. LV patent LV 4495 B / LV patents Nr. 445, B, klase H0K9/06. Stieņu induktormašīna. // A.Terebkovs (LV), J.Greivulis (LV), A.Gasparjans (LV), J.Doniņš (LV) // Latvijas Republikas Patentu Valde, LV patents Nr. 445, B, class H0K9/06. Bar-type inductor machine. // A.Terebkovs (LV), J.Greivulis (LV), A.Gasparjans (LV), J.Doniņš (LV) // Patents Board of Latvian Republic, (In Latvian) 4. Daskova-Golovkina J., Levins N., Puacevs V. Electrical enerators of modern WPP. Power and Electrical Enineerin International Conference, Ria, RTU, October, Daskova-Golovkina J., Levins N., Puacevs V. Multipole Synchronous Generators with Permanent Manets and tooth windin for low-power WPP. 5 th International CPE 007 Compatibility in Power Electronics Poland, Gdansk, Axial Generator Calculator V.3. [online][0..0] Available at: 7. Нейман Л.Р., Демирчян К.С. Теоретические основы электротехники. М.-Л., Энергия L.R. Neiman, K.S. Demirchjan. Theoretical fundamentals of electrical enineerin, 5 p. (In Russian). 434

Martynov V.V., Trushakov D.V., Kirovograd National Technical University, Kirovograd, Ukraine

METHOD OF ELECTION OF FREQUENCY FOR ELECTROMAGNETIC FIELD OF EDDY-CURRENT TRANFORMER WITH U-TYE CORE BY IT INTERACTION WITH A TETED FERROMAGNETIC ECIMEN Martynov V.V., Trushakov D.V., Kirovorad National