The Online-Measurement System Design for the Temperature Rise of AC Motor Winding Based on FFT

Transcription

1 Researc Journal of Applied Sciences, Engineering and Tecnology (): -, ISSN: - Maxwell Scientific Organization, Submitted: May, Accepted: June, Publised: November, Te Online-Measurement System Design for te Temperature Rise of AC Motor Winding Based on FFT Haiong Xiao and Zenjun Li Department of Electrical and Information, Department of Mecanical Engineering, Henan institute of engineering, Zenzou, Cina Abstract: It is important to measure te temperature rise of AC motor winding and te common metod as many sortcomings, terefore te new design for measuring te temperature rise is necessary. Te paper mainly discusses te online-measurement system design for te temperature rise of AC motor winding based on FFT. Te principle of measuring temperature rise, measuring power and current based on FFT are given in te study. At te same, some ard ware s, te main program flow cart and te testing results are given. Te result sows tat te design feasible. Keywords: Current, FFT, power, temperature rise INTRODUCTION According to te People s Republic of Cina standard of EN- and GB.-, it is necessary to measure te value of AC motor winding temperature rise for getting te AC motor s efficiency and calculating te loss of motor winding eat. At te same time, excessive temperature rising will cause te security idden danger to Electrical system and lead to te accident occur. Formerly, te measurement metod is to test te DC resistance of te AC motor winding in cold and ot state s for calculating te temperature rising. Tis metod to test temperature rising lead to te AC motor must be turned off te power firstly and te error caused by time delay will produce and te metod must ave been calculated, draw projections (Zang and Li, ). At present, te major intelligent instrument to test temperature rising tat exist in market uses an additional direct current source metod, wic is to measure voltage and resistance of winding to find temperature (Yao and Si, ). But tis kind of instrument as been complicated in structure, troublesome in use, ig in cost, single in function. So, it is necessary to design a simple, practical, multifunction, online-measurement instrument. Tis paper discusses te resistance of te online-measurement instrument to test te temperature rising (Sun, ; Dong, ; Song et al., ). Troug to te sampling of AC voltage and current and using FFT conversion work out active power of te windings, find out resistance and te temperature rising of windings. Tis system in addition to measure temperature winding, Also can measure motor line voltage, and current and armonic content, meanwile it ave a broad market prospect. WINDING TEMPERATURE MEASURING PRINCIPLE AND THE WHOLE SYSTEM DESIGN Motor winding temperature measurement and AC sample principle: Motor winding temperature rising measurement principle According to te national Standard of EN- and GB.-.Motor winding temperature measurement formula is: R R T= K + T T T R ( ) ( ) were, T = Te Winding's temperature rising R = Resistance of winding in cold state R = Resistance of winding in ot state K = Constant, K =, wit C U winding, K = wit A L winding T = Te temperature of cold state T = Te temperature of ot state Because: () P R = () I Corresponding Autor: Department of Electrical and Information, Henan Institute of Engineering, Zenzou, Cina

2 Res. J. Appl. Sci. Eng. Tecnol., (): -, Current sampling Voltage sampling processing processing A/D convert Cortex-M STM Temperature detection and te oters sift PLL Keyboard Fig. : Te overall blog diagram So: I P I P T = ( K + T ) ( T T ) () IP In equation (),P,P,I,I are te power and current value wic are measured in cold state and ot state, (I, I :I P in delta connection, I L in star connection). T, T are te same wit equation (). Te power and te current measurement principle based on FFT Te signal waveform is discretized into: a yt a t b t () N () = + ( k = cosω + sin ω ) N T π a = y( k )cos( k) N K = N N N T π b = y( k )sin( k) N N N K = Harmonic amplitude for times: c = a + b () a Pase angle: φ = arctg () b According to above equation for times: U = a + b I = a + b U RMS: N / U = U = () I RMS: N / I = I () = Power for pase C: P = U I + U I cosϕ () C = Power for pase A: P = U I + U I cosϕ () A = P = P + P ALL Te power on eac winding: PALL P = () Te design of overall system: Te system mainly consist of voltage sampling, current sampling, temperature detection, display, keyboard, communication, PLL, and Cortex-M STM interface wit A/D etc. Te overall block diagram is as Fig.. In Fig., two of te tree pase current (I A, I C ), voltage (U AB, U CB ) are sampled by CT and PT. Troug te same signal processing, te two sampling signal amplitude are sifted to fit to te A/D (max). In te design, te PLL is designed to proceed te syncronous signal wic te out frequency is te N times to te input frequency and te syncronous signal is sent to STM, to be used to start te A/D converter. Te Cortex-M STM is te mainly CPU, wic is used to control te wole ardware system and calculate te voltage, current and power in RMS wit FFT. On te oter and, STM is used to measure te temperature wit te embedded A/D, to display, to communicate, to store te data, etc.

3 Res. J. Appl. Sci. Eng. Tecnol., (): -, THE DESIGN OF SYSTEM HARDWARE Te system ardware consists of te voltage sampling, te current sampling, display, signal (rate) output s, communication, etc. Because communication, display, key using conventional s, terefore, witout discourse in tis paper. Te design of Voltage, current sampling : Te current sampling sown in Fig., te voltage sampling uses te same, wic convert te voltage to te current firstly. Current transformer wit ig accuracy, wide range of CT. Wen inputs current being A, te current transformer outputs ma. CT transformer in series resistance Ω to get V voltage., Beind te voltage amplification, te input signal to te back of V, make te system able to receive te impact of te current rated %. Te voltage transformer as complex structure and te price is too ig. So te voltage sampling uses te same te current sampling wit series resistance in te current transformer Fig. : Current sampling + - UA R LMJG K C.uF D N + PH CMPR CI VDD CMPR IN PH CMPR SIG IN R K DMD CI PH PULSES C VCO IN pf R TO RK VCO OUT R TO INH ZENER R K C nf U HCFBEY Output VDD Q Q Q Q Q Q Q Q Q CLK Q U CDBCN CLK CLK RST Fig. : Te PLL

4 Res. J. Appl. Sci. Eng. Tecnol., (): -, Uab Ia Ucb Ic PA INT PD PA PA U CHA CHB CHA CHB CHA CHB CHA CHB CLK CONVST INT CS RD WR AVDD DVDD AVSS D/A(LSB) D/A D/A D/A D D D D D D D D D D(MSB) A A REFIN D REFOUT MAXACAX U OE VCCB PA DIR VCCB +V VCCA C D A B D A B D A B D A B D A B D D A B D D A B D D A B D D D D D D SNLVCDB D +V D U D OE VCCB D DIR VCCB D VCCA D A B D A B D A B D A B D A B D A B INT A B CLK A B SNLVCDB UA INT SNLSD PC PC PC PC PC PC PC PC V V +V PC PC PC PC PC PC PA PA INT PA PA PA PA PA PA PA PA PA PA PA PA PA PA PA PA PD BOOT RESET V U PA-WKUP PA PA PA PA PA PA PA PA PA PA PA PA PA/JTMS/SWDIO PA/JTCK/SWCLK PA/JTDI OSC_IN/PD OSC_OUT/PD PD BOOT NRST VBAT VDD_ VDD_ VDD_ VDD_ VDDA STMFRBT PB PB PB/BOOT PB/JTDO PB/JNTRST PB PB PB PB PB PB PB PB PB PB PB PC PC PC PC PC PC PC PC PC PC PC PC PC PC-TAMPER-RTC PC-OSC_IN PC-OSC_OUT VSS_ VSS_ VSS_ VSS_ VSSA PB PB PB PB PB PB PB PB PB PB PB PB PB PB PB PB PC PC PC PC PC PC PC PC PC PC PC PC PC PC PC PC Fig. : A/D and cortex-m interface Te design of PLL : Te PLL is designed for sampling voltage and current signal in equal interval time, te principle is sown as Fig.. In Fig., te LM is used to cange analog sine signal to square wave signal and te CD is used for an divider wit. CD is a PLL IC, wic te output signal is times frequency to te frequency. Te design of te STM interface wit A/D convert: Two A/D cip named MAX are used in te measurement system, te interface wit Cortex-M is as Fig.. Tree pase voltage and current signals are converted by two MAX, wic outputs te igest level is V. So an IC cip AHCT is necessary to matc te.v voltage level of STM. Two AHCT are used in tis as level sifter unit. AHCT output signals and input signals are connected, respectively to MAX and STM wit -bit DBUS. Te control signals voltage level is matced just as data signal. Equally spaced signal tat comes from PLL and te signal of A/D conversion completed are sifted by AHCT.Te signals tat two MAX receive, respectively are U AB, U CB, I A and I C. Te design of system software: Te system software is used to measure te power of eac winding, te current, te temperature, to complete FFT calculation, and to calculate te temperature rising of winding. Te subroutines in te internal library of Cortex-M are applied as calculation program. Te flow cart is sown in Fig.. In te main flow carts, initialization of te system is firstly been done. Ten oter work will be done One by one. Te oter study concludes starting A/D to complete sampling times in one voltage cycle, calculating te power and te current of eac winding, calculating te temperature rising of one winding, etc. At te specific time, te power, current, room temperature are stored in flas memory to be used to calculate te winding temperature rising. Te metod to test te system and te experimental result: To test te performance of te system, AC motor named YS is been used in no-load state and wit Laboratory temperature condition. Te HP is used to test te resistance of eac winding in cold and ot state, and te system is used to test te power and current, te test data is sown in Table. In Table cold state is defined at te time tat te motor start to work, and te ot state is defined te motor works one our after. Te data is respectively substituted into Eq. () and (), to calculate te temperature rise tat is named as T.

5 Res. J. Appl. Sci. Eng. Tecnol., (): -, Start Initialization Sampling interrupt? Complete times sampling Calculate power, current and test room temperature Store te P and I and T in cold or ot state experimental results sow tat te system as ig accuracy, low cost, convenient debug, aving a broad application prospect. ACKNOWLEDGMENT In te design process, Xu Yuwei, studying in te Electronic and information Department, Henan institute of engineering, do a lot of work in te ardware and software design. In te tesis writing process, He Yongtao gave me a lot of elp, expressing gratitude togeter. REFERENCES Store te data in te specific time? Calculate temperature rising End te test Fig. : Main flow cart of te system Table : Te testing data Resistance Power of eac pase Current Cold state... Hot state... T.. In Table, te room temperature is defined to C,te calculating result sows te temperature rise are te same wit te two measuring metod. Dong, G.,. Measurement and Calculation of te Motor Winding Temperature Rise. Suzou Institute of Trade and Commerce, Suzou, Cina. Song, Q., W. Zi-fu, Z. Ceng-ning and S. Feng-cun,. Measurement of Motor Winding Temperature Based on Zero Second Resistance Fitting. Scool of Mecanical and Veicular Engineering, Beijing Institute of Tecnology, Beijing, Cina. Sun, Y.,. Measurement of te motor winding temperature rise. Elect. Meas. Ins., Vol: pp. Yao, X. and R. Si,. Te Design of Online Test Instrument of Motor winding temperature rise. Microelectron. Comp., Vol: pp. Zang, J. and J. Li,. Te application of single board computer in measuring temperature rise of motor winding. Micro motor, Vol: pp. CONCLUSION Tis system is designed for measuring te temperature rising of AC motor winding, te