Masu ba da kayan aikin mai jujjuya mitoci suna tunatar da ku cewa an yi amfani da masu sauya mitar sosai wajen samar da masana'antu a yau. Kayan aikin da masu sauya mitoci ke sarrafawa na iya adana makamashi sosai zuwa wani ɗan lokaci, don haka samun tagomashin masana'antun masana'antu da yawa.
Don cimma fasali kamar filin ajiye motoci mai laushi, farawa mai laushi, ƙa'idodin saurin tafiya, ko buƙatu na musamman don haɓakawa ko rage gudu, ana buƙatar na'urar sarrafa saurin da ake kira mai sauya mitar a cikin injinan asynchronous na zamani. Babban da'irar na'urar tana amfani da da'irori AC-DC-AC tare da mitar aiki na 0-400Hz. Ƙarfin wutar lantarki na ƙananan ƙarfin wutar lantarki na duniya mai juyawa shine 380-460V, kuma ƙarfin fitarwa shine 0.37-400kW.
Zaɓi madaidaicin mai sauya mitoci
Matsalolin da ke tasowa yayin amfani da na'urori masu sauya mitoci, kamar aiki mara kyau, gazawar kayan aiki, da sauransu, wanda ke haifar da dakatarwar samarwa da asarar tattalin arziƙin da ba dole ba, galibi ana haifar da su ta hanyar zaɓi mara kyau da shigar da na'urori masu juyawa. Sabili da haka, ya zama dole don zaɓar mai canzawa na tattalin arziƙi da mai amfani wanda zai iya mafi dacewa da yanayin asali da buƙatun samarwa da tsari.
A matsayin babban abin tuƙi na mai sauya mitar, yakamata a zaɓi motar don dacewa da sigogin aiki na injin lokacin zabar nau'in mai sauya mitar.
(1) Matching Voltage: Ƙwararren wutar lantarki na mai sauya mitar ya dace da nauyin nauyin motar.
(2) Current matching: The capacity of the frequency converter depends on the rated current continuously output by the frequency converter. When selecting a frequency converter for motors that require speed regulation, it is necessary to choose a frequency converter with a continuous rated current greater than the rated current of the motor when operating at rated parameters, and with a quantitative margin; For general frequency converters with more than 4 poles, the selection cannot be based on the capacity of the motor, but on the current seat verification standard of the motor; Even if the load on the motor is relatively light and the current is less than the rated current of the frequency converter, the selected frequency converter cannot be too small in capacity compared to the motor.
(3) Capacity matching: Depending on the different load characteristics of the motor, there are different requirements for selecting the capacity of the frequency converter.
Control method of frequency converter
The main control methods of frequency converters currently include the following.
(1) The first generation used U/f=C control, also known as sine pulse width modulation (SPWM) control method. Its characteristics include a simple control circuit structure, low cost, good mechanical properties and hardness, which can meet the smooth speed regulation requirements of general transmission. However, this control method reduces the maximum output torque at low frequencies due to the lower output voltage, resulting in decreased stability at low speeds. Its characteristic is that without feedback device, the speed ratio ni is less than 1/40, and with feedback, ni=1/60. Suitable for general fans and pumps.
(2) The second generation adopts voltage space vector control (magnetic flux trajectory method), also known as SVPWM control method. It is based on the overall generation effect of three-phase waveforms, generating three-phase modulation waveforms at once and controlling them by cutting polygons to approximate circles. To eliminate the influence of stator resistance at low speeds, the output voltage and current are closed loop to improve dynamic accuracy and stability. Its characteristics: no feedback device, speed ratio ni=1/100, suitable for speed regulation in general industry.
(3) The third generation adopts vector control (VC) method. The practice of vector control variable frequency speed regulation essentially equates an AC motor to a DC motor, and independently controls the speed and magnetic field components. By controlling the rotor magnetic flux and decomposing the stator current to obtain two components, torque and magnetic field, orthogonal or decoupled control can be achieved through coordinate transformation. Its characteristics: speed ratio ni=1/100 without feedback, ni=1/1000 with feedback, and starting torque of 150% at zero speed. It can be seen that this method is applicable to all speed control, and when equipped with feedback, it is suitable for high-precision transmission control.
(4) Direct Torque Control (DTC) method. Direct torque control (DTC) is another high-performance variable frequency speed control mode that differs from vector control (VC). Obtain magnetic flux and torque data using magnetic flux simulation models and electromagnetic torque models, compare them with given values to generate hysteresis comparison state signals, and then switch the switch state through logic control to achieve constant magnetic flux control and electromagnetic torque control. It does not require imitation of DC motor control, and this technology has been successfully applied to the AC drive of traction electric locomotives. Its characteristics: without feedback device, the speed ratio ni=1/100, with feedback ni=1/1000, and the starting torque can reach 150% to 200% at zero speed. Suitable for heavy-duty starting and large loads with constant torque fluctuations.
Installation environment requirements
(1) Environmental temperature: The environmental temperature of the frequency converter refers to the temperature near the cross-section of the frequency converter. Due to the fact that frequency converters are mainly composed of high-power power electronic devices that are highly susceptible to temperature, the lifespan and reliability of frequency converters largely depend on temperature, generally ranging from -10 ℃ to+40 ℃. In addition, it is necessary to consider the heat dissipation of the frequency converter itself and the extreme situations that may occur in the surrounding environment, and a certain margin is generally required for temperature.
(2) Environmental humidity: The frequency converter requires a relative humidity of no more than 90% in its surrounding environment (with no condensation on the surface).
(3) Jijjiga da girgiza: Yayin shigarwa da aiki na mai sauya mitar, ya kamata a biya hankali don guje wa girgiza da girgiza. Don guje wa haɗin haɗin siyar da sassan sassa na ciki na mai sauya mitar, wanda zai iya haifar da rashin kyawun sadarwar lantarki ko ma munanan laifuffuka kamar gajerun kewayawa. Sabili da haka, yawanci ana buƙata cewa haɓakawar girgizar wurin shigarwa ya iyakance zuwa ƙasa da 0.6g, kuma ana iya ƙara matakan juriya na girgiza kamar roba mai ɗaukar girgiza a wurare na musamman.
(4) Wurin shigarwa: Matsakaicin izinin fitarwa na halin yanzu da ƙarfin lantarki na mai sauya mitar yana tasiri ta iyawar zafinsa. Lokacin da tsayin daka ya wuce 1000m, ƙarfin watsar da zafi na mai sauya mitar zai ragu, don haka ana buƙatar mai sauya mitar gabaɗaya don shigar da shi ƙasa da tsayin mita 1000.
(5) Abubuwan buƙatu na gabaɗaya don shigar da wurin mai sauya mitar sune: babu lalata, babu iskar gas mai ƙonewa ko fashewar abubuwa; Ƙura mara ƙura, zaruruwa masu iyo da barbashi na ƙarfe; Guji hasken rana kai tsaye; Babu tsangwama na lantarki.
Bincike kan ka'idojin saurin mitar mai canzawa a halin yanzu shine mafi aiki kuma a zahiri aiki mai kima a cikin binciken watsa wutar lantarki. Yiwuwar masana'antar sauya mitar tana da girma, saboda ana amfani da ita sosai a masana'antu kamar kwandishan, lif, ƙarfe, da injina. Canjin saurin mitar mai sarrafa injina da madaidaitan masu musanya su za su haɓaka cikin sauri.