Umphakeli weyunithi yempendulo ukukhumbuza ukuthi kusukela kwavela ama-motor induction azenzakalelayo, uhlobo lwamajeneretha e-AC seluvele lwenziwe ukusebenza okuguquguqukayo. Shintsha isivinini sejeneretha bese ulungisa imvamisa yokuphuma kwayo. Ngaphambi kokuvela kwe-high-speed transistors, lokhu kwakungenye yezindlela eziyinhloko zokushintsha isivinini semoto, kodwa ngenxa yejubane le-generator linciphisa imvamisa yokuphuma esikhundleni se-voltage, ukuhluka kwemvamisa kwakulinganiselwe.
Ngakho-ke, ake sibheke izingxenye ze-converter ye-frequency futhi sibone ukuthi empeleni zisebenzisana kanjani ukushintsha imvamisa nesivinini semoto.
Izingxenye ze-inverter - isilungisi
Ngenxa yobunzima bokushintsha imvamisa yamagagasi e-AC sine kumodi ye-AC, umsebenzi wokuqala wesiguquli semvamisa ukuguqula i-waveform ibe yi-DC. Ukwenza ibukeke njenge-AC, kulula ukuyisebenzisa i-DC. Ingxenye yokuqala yazo zonke iziguquli zefrikhwensi iyithuluzi elibizwa ngokuthi i-rectifier noma isiguquli. Isekhethi yokulungisa kabusha yesiguquli se-frequency iguqulela i-alternating current ibe eyamanje eqondile, futhi imodi yayo yokusebenza icishe ifane neyeshaja yebhethri noma umshini wokushisela i-arc. Isebenzisa ibhuloho le-diode ukukhawulela igagasi le-AC sine ukuthi lihambe liye ohlangothini olulodwa kuphela. Umphumela uba ukuthi i-waveform ye-AC elungiswe ngokugcwele ihunyushwa yisekethe ye-DC njenge-waveform ye-DC yendawo. Isiguquli sefrikhwensi yezigaba ezintathu samukela izigaba zokufaka ze-AC ezizimele ezintathu futhi ziziguqule zibe okukhiphayo okukodwa kwe-DC.
Iziguquli eziningi zezigaba ezintathu zefrikhwensi zingaphinda zamukele ugesi wesigaba esisodwa (230V noma 460V), kodwa ngenxa yamagatsha okokufaka amabili kuphela, okukhiphayo (HP) kwesiguquli sefrikhwensi kufanele kwehliswe ngoba i-DC ekhiqiziwe yamanje incishiswe ngokulinganayo. Ngakolunye uhlangothi, i-inverter yangempela yesigaba esisodwa (i-inverter yesigaba esisodwa elawula injini yesigaba esisodwa) isebenzisa okokufaka kwesigaba esisodwa futhi ikhiqize okukhiphayo kwe-DC ngokulingana nokokufaka.
Kunezizathu ezimbili zokuthi kungani ama-motor ezigaba ezintathu asetshenziswa kakhulu kunezingxenye eziphikisayo zesigaba esisodwa uma kuziwa ekusebenzeni kwejubane eliguquguqukayo. Okokuqala, banobubanzi bamandla abanzi. Ngakolunye uhlangothi, amamotho esigaba esisodwa ngokuvamile adinga ukungenelela kwangaphandle ukuze aqale ukujikeleza.
Izingxenye ze-Inverter - ibhasi le-DC
Ingxenye yesibili yebhasi le-DC ayikwazi ukubonakala kunoma iyiphi i-converter ye-frequency ngoba ayithinti ngokuqondile ukusebenza kwesiguquli semvamisa. Kodwa-ke, ihlala ikhona kuziguquli zekhwalithi ephezulu zenhloso ejwayelekile. Ibhasi le-DC lisebenzisa ama-capacitor nama-inductors ukuze lihlunge i-AC "ripple" voltage kumandla aguquliwe e-DC, bese lingena esigabeni se-inverter. Kuhlanganisa futhi isihlungi sokuvimbela ukuhlanekezela kwe-harmonic, okungabuyiselwa kugesi we-inverter. Iziguquli zamafrikhwensi amadala zidinga izihlungi zolayini ezihlukene ukuze ziqedele le nqubo.
Izingxenye ze-Inverter - Inverter
Ngakwesokudla somfanekiso "izitho zangaphakathi" zesiguquli semvamisa. Isiguquli sisebenzisa amasethi amathathu ama-transistors ashintshayo anesivinini esikhulu ukudala zonke izigaba ezintathu ze-DC "pulses" ezilingisa amaza e-AC sine. Lawa ma-pulses awanqumi kuphela i-voltage ye-wave, kodwa futhi nemvamisa yayo. Igama elithi 'inverter' lisho' ukuhlehla ', okusho nje ukunyakaza okuya phezulu naphansi kwe-waveform ekhiqiziwe. Iziguquli zamafrikhwensi zanamuhla zisebenzisa indlela ebizwa ngokuthi "i-pulse width modulation" (PWM) ukulawula i-voltage kanye nemvamisa.
Bese sikhuluma nge-IGBT. I-IGBT ibhekisela "ku-insulated gate bipolar transistor", okuyingxenye yokushintsha (noma i-pulse) ye-inverter. Ama-Transistors (ashintsha amashubhu e-vacuum) adlala izindima ezimbili emhlabeni wethu we-elekthronikhi. Ingenza njenge-amplifier futhi ikhulise isignali, noma ingasebenza njengeswishi ngokumane ivule futhi ivale isignali. I-IGBT inguqulo yesimanje ehlinzeka ngesivinini sokushintsha esiphezulu (3000-16000 Hz) futhi inciphisa ukukhiqizwa kokushisa. Isivinini sokushintsha esiphezulu singathuthukisa ukunemba kokulingiswa kwegagasi le-AC futhi sinciphise umsindo wemoto. Ukunciphisa ukushisa okukhiqizwa kusho ukuthi isinki sokushisa sincane, ngakho-ke isiguquli semvamisa sithatha indawo encane.
Inverter PWM waveform
I-waveform ekhiqizwe i-inverter yesiguquli se-PWM uma iqhathaniswa negagasi langempela le-AC sine. I-inverter ephumayo iqukethe uchungechunge lwama-pulses angunxande anobude obugxilile nobubanzi obulungisekayo.
Kulesi simo, kukhona amasethi amathathu ama-pulses - isethi ebanzi phakathi nendawo kanye nesethi encane ekuqaleni nasekupheleni kwezingxenye ezinhle nezingezinhle zomjikelezo we-AC.
Isamba sezindawo zama-pulses silingana ne-voltage esebenzayo yegagasi le-AC langempela. Uma ufuna ukusika izingxenye ze-pulse ngenhla (noma ngezansi) i-waveform yokuxhumana yangempela bese ugcwalisa indawo engenalutho ngaphansi kwejika ngazo, uzothola ukuthi zicishe zifane ngokuphelele. Kungale ndlela kanye lapho isiguquli semvamisa sikwazi ukulawula i-voltage yemoto. Isamba sobubanzi be-pulse nobubanzi obungenalutho phakathi kwakho sinquma imvamisa ye-waveform ebonwa injini (yingakho i-PWM noma i-pulse wide modulation). Uma ukushaya kwenhliziyo kuqhubekayo (okungukuthi ngaphandle kwezikhala), imvamisa isazolunga, kodwa i-voltage izoba nkulu kakhulu kunegagasi le-AC sine langempela.
Ngokusho kwe-voltage edingekayo kanye nemvamisa, isiguquli semvamisa sizoshintsha ubude nobubanzi be-pulse, kanye nobubanzi obungenalutho phakathi kwakho kokubili. Abanye abantu bangase bazibuze ukuthi le 'AC' mbumbulu (empeleni i-DC) iyisebenzisa kanjani i-AC induction motor.
Phela, ingabe i-alternating current idinga "ukuyenga" inkambu yamanje kanye nehambisanayo kazibuthe ku-rotor yemoto? Ngakho-ke, i-AC izodala ukungeniswa ngokwemvelo ngoba iyindlela eshintsha njalo, kuyilapho i-DC ingeke isebenze ngokujwayelekile uma isekethe isicushiwe.
Kodwa-ke, uma i-DC ivuliwe futhi ivaliwe, ingakwazi ukuzwa okwamanje. Kulabo asebekhulile, isistimu yokuthungela imoto (ngaphambi kokushisa kwe-solid-state) yayivame ukuba nesethi yamaphuzu kumsabalalisi. Inhloso yala maphuzu ukusuka ku-"pulses" yebhethri kuya kumakhoyili (ama-transformers). Lokhu kubangela ukuthi ikhoyili ishaje bese inyusa i-voltage ibe sezingeni elivumela ukuthi i-spark plug ivutha. I-pulse ye-DC ebanzi ebonwe kulesi sibalo esingenhla empeleni yenziwe ngamakhulu ama-pulses angawodwana, futhi ukunyakaza kokuvula nokuvala kokuphuma kwe-inverter kuvumela ukungeniswa kwe-DC ukuthi kwenzeke.
I-voltage esebenzayo
Isici esisodwa esenza inkimbinkimbi yamanje eshintshashintshayo ukuthi ishintsha njalo i-voltage, isuka kuziro iye ku-voltage ephezulu ephozithivu, bese ibuyela ku-zero, bese iye ku-voltage ethile ephezulu engalungile, bese ibuyela ku-zero. Indlela yokunquma i-voltage yangempela esetshenziswe kumjikelezo? Umfanekiso ongezansi ungu-60Hz, 120V sine wave. Kodwa kufanele kuqashelwe ukuthi i-voltage yayo ephezulu ingu-170V. Uma i-voltage yayo yangempela ingu-170V, singayibiza kanjani igagasi elingu-120V?
Isici esisodwa esenza inkimbinkimbi yamanje eshintshashintshayo ukushintsha kwayo njalo ku-voltage, isuka ku-zero iye ku-voltage ephezulu ephozithivu, bese ibuyela ku-zero, bese ifinyelela ku-voltage ethile ephezulu kakhulu engalungile, bese ibuyela ku-zero. Indlela yokunquma i-voltage yangempela esetshenziswe kumjikelezo?
I-60Hz, 120V sine wave kufanele kuqashelwe ukuthi i-voltage yayo ephezulu ingu-170V. Uma i-voltage yayo yangempela ingu-170V, singayibiza kanjani igagasi elingu-120V?
In one cycle, it starts at 0V, rises to 170V, and then drops again to 0. It continues to drop to -170, and then rises again to 0. The area of the green rectangle with an upper boundary of 120V is equal to the sum of the areas of the positive and negative parts of the curve.
So 120V is the average level? Okay, if we were to average all the voltage values at each point throughout the entire cycle, the result would be approximately 108V, so it cannot be the answer. So why is this value measured by VOM at 120V? It is related to what we call 'effective voltage'.
If you want to measure the heat generated by the direct current flowing through a resistor, you will find that it is greater than the heat generated by the equivalent alternating current. This is because AC does not maintain a constant value throughout the entire cycle. If conducted under controlled conditions in the laboratory, it is found that a specific DC current produces a 100 degree heat increase, resulting in a 70.7 degree increase in AC equivalent or 70.7% DC value.
So the effective value of AC is 70.7% of DC. It can also be seen that the effective value of the AC voltage is equal to the square root of the sum of the squares of the voltages in the first half of the curve. If the peak voltage is 1 and various voltages from 0 degrees to 180 degrees need to be measured, the effective voltage will be the peak voltage of 0-707 degrees. 0.707 times the peak voltage of 170 in the figure is equal to 120V. This effective voltage is also known as root mean square or RMS voltage.
Therefore, the peak voltage is always 1.414 of the effective voltage. 230V AC current has a peak voltage of 325V, while 460 has a peak voltage of 650V. In addition to frequency variation, even if the voltage is independent of the operating speed of the AC motor, the frequency converter must also change the voltage. Two 460V AC sine waves. The red curve is 60Hz, and the blue curve is 50Hz. Both have a peak voltage of 650V, but 50Hz is much wider. You can easily see that the area within the first half of the 50Hz curve (0-10ms) is larger than the first half of the 60Hz curve (0-8.3ms). Moreover, as the area under the curve is directly proportional to the effective voltage, its effective voltage is higher. As the frequency decreases, the increase in effective voltage becomes more severe.
Uma ama-motor angu-460V evunyelwe ukusebenza kulawa ma-voltage aphezulu, isikhathi sawo sokuphila singancishiswa kakhulu. Ngakho-ke, isiguquli se-frequency kufanele sishintshe njalo i-voltage "esiqongweni" esihlobene nemvamisa ukuze sigcine i-voltage esebenzayo engaguquki. Lapho i-frequency yokusebenza iyancipha, i-voltage ephezulu yehla, futhi ngokuphambene nalokho. Manje kufanele uqonde kahle isimiso sokusebenza se-converter frequency kanye nendlela yokulawula isivinini semoto. Iziguquli zefrikhwensi eziningi zivumela abasebenzisi ukuthi bazihlelele isivinini semoto ngokushintsha izindawo eziningi noma amakhibhodi, noma basebenzise izinzwa (ingcindezi, ukugeleza, izinga lokushisa, ileveli yoketshezi, njll.) ukuze benze inqubo ngokuzenzakalelayo.