【作者】 路萍；

【导师】 元哲石；

【作者基本信息】 吉林大学 ， 材料加工工程， 2012， 硕士

【摘要】 工业加热在现代工业加工技术中占有一席重要的位置。在生产很多产品的过程中，都离不开加热这道工序。例如加工锻造金属的过程、塑料制品的加工成型等。传统的加热生产方式通常是燃烧一些可燃物质产生热量从而达到对加热对象加热的目的。虽然这些加热方式仍然被广泛的应用在各种领域，但是这些加热方式很显然是存在很多问题的，例如占用空间大、效率低，而且加热过程中严重污染环境。当然，在现代工业中，利用电能加热也是非常广泛的，但它属于接触性加热，会造成金属材料氧化，致使加热不均匀等问题。在这样的情况下，新的加热方法的产生是必然的。这种新兴的加热方式就是感应加热，属于非接触式加热。感应加热的工作原理是利用高频的电场或磁场对工件等进行加热，不会造成金属氧化等等问题，大大满足了现代工业生产高效率的要求，同时，感应加热在节省能源，降低工业对环境的污染和破坏方面也很有优势，具有很广阔的市场前景。人们最早在电动机、发电机、变压器中就已经应用了电磁感应原理，但是，处于交变磁场中的导体不但会产生感应电流，还会产生热量，人们将这种发热看作是能量的损耗，想尽一切办法减少这种发热。直到十九世纪末，科学家对涡流效应进行了深入的探讨和研究之后，才真正意识到其应用价值。感应加热的理论基础由此开始慢慢建立起来。20世纪50年代初，我国就开始将感应加热技术应用于工业生产中。国内首台晶闸管中频电源诞生于浙江大学，并且已经在生产中得到了广泛的应用。20世纪80年代，超音频电源（50kW/50kHz）研制成功；20世纪90年代，50kW/50kHz的IGBT电流型和30kW/300kHZ的MOSFET感应加热电源投入生产。随着晶闸管的出现，以固态半导体器件为核心的现代电力电子学开始快速发展。之后兴起的新型自关断电子元器件，如MOS晶闸管、绝缘栅双极晶体管（IGBT）、静电感应晶体管、MOSFET场效应晶体管等的广泛使用，又掀起了中、高频感应加热领域的又一次革命。目前，感应加热技术正在向功率更大、频率更高的领域进军，不久的未来，感应加热电源将实现计算机化、在线自动化和整装化。本论文设计的是小功率逆变式感应加热电源。逆变电源的工作原理主要是将220V交流电通过整流电路、滤波电路之后变成直流电，输入到逆变主电路中，逆变主电路中的场效应晶体管MOSFET在控制电路发出的脉冲作用下，按照一定的频率导通或者截止，从而输出一定频率的交流电。该交流电必须再经过变压器，变成电压和电流大小合适的交流电输入到负载回路中，从而实现感应加热。本论文设计的感应加热电源的参数是：输出振荡频率：f=100~250kHz；输出振荡电流：I2=100~200A；输出振荡功率：P2=4KVA；效率：η=80%；负载持续率：FSe＝50％；冷却水要求为0.2MPa-5L/min。由于本论文设计的感应加热电源的频率较高，需要频繁导通开关管，并且要实现零电流关断，所以选择了串联型谐振逆变结构。在功率开关器件的选择上，选择了场效应晶体管MOSFET作为开关器件，因为MOSFET所需要的驱动功率较小，开关速度快，工作频率高，具有较好的热稳定性和抗干扰能力，适用于功率较小的场合。根据给定的设计参数计算，变压器采用的是一对型号为EE55的铁氧体铁芯；原边匝数为31匝，采用35根直径为0.41mm的漆包线并联绕制；副边为2匝，采用4根空心黄铜管并联，黄铜管的外半径为8.69mm，内半径为8.03mm。这样可以有效的避免集肤效应，并且可以及时降低输出线圈的温度。主电路包括启动缓冲电路，滤波电路和MOSFET场效应晶体管逆变主电路。本论文设计的是小功率感应加热电源，所以选择了单相不可控整流电路。经过整流的不平滑电压再经过滤波电路的处理变成平滑的直流310V电压供给逆变主电路。值得一提的是，电路中设置了缓冲电路，可以避免合闸瞬间产生的浪涌电流对电路中的各个电容造成损害，启动电源，逆变主电路正常工作后，限流电阻会被短接，防止产生功率损耗。这个缓冲的时间非常短。逆变主电路中采取的是三个MOSFET并联作为一个桥臂开关管，从而提高电源的输出容量。并且在开关管两端并联了电容和电阻以起到避免瞬间电压过大而损坏开关管的目的。控制电路是整个感应加热电源的核心，控制电路起到的作用主要是产生脉冲提供给驱动电路从而驱动场效应晶体管MOSFET按照一定的频率导通或者截止，最终输出满足要求的交流电供给负载回路。脉冲是通过脉宽调制器KA3525产生的。在这个过程中，需要同步跟踪负载回路，从而防止谐振频率漂移而造成的负载特性变化，使脉冲频率与负载谐振回路的谐振频率保持一致。该电路还设有电流反馈和输出功率调节电路，通过改变脉冲频率调节输出功率。另一方面，电流互感器接收电流信号，根据电流反馈信号调节脉冲频率从而达到稳定输出的目的。最重要的一点是控制主电路设有死区时间，防止开关管出现直通现象，避免直通造成逆变失败以及开关管的损坏。控制电路还包括过流、过压、过热保护电路以及故障反馈电路，有效地保证了感应加热电源的稳定工作。当然，控制电路中还包括各部分电源电路和启动以及显示电路，保证电路的基本功能。最后对感应加热电源进行了工艺实验，分别测量了在不同频率下，触发脉冲产生波形和MOSFET触发脉冲波形以及变压器输出电压波形，通过对波形的分析，验证了本论文设计的电源电路达到了设计要求。更多还原

【Abstract】 Industrial heating occupies a seat on an important position in the modern industrialprocessing technology. In the production of many products，for example， the processof forging metal and plastic products，the heating process is necessary. Usually，theburning of combustible material，which can generate heat so as to achieve the purposeof heating on the heated object，is used in the traditional heating mode of production.Although these heating methods are widely used in various fields，but there are a lot ofproblems about them, such as space， low efficiency and serious pollution of theenvironment during the heating process. Of course， in modern industry， heating byelectric is also very extensive， but it is a contact heating that will cause the metaloxidized and result in uneven heating，ect.，The generation of new heating method isinevitable in such circumstances.This new way of heating is induction heating, belonging non-contact heating filed.The induction heating, which will not cause the metal oxidized, hates the workpiece byusing high-frequency electric or magnetic field of it. It is able to satisfy therequirements of the high efficiency of modern industrial production. At the same time,the induction heating, which has great advantage to save energy, reduce industrialenvironmental pollution and destruction, has a very broad market prospects.The electromagnetic induction principle have been earliest used in motors,generators and transformers, but the conductor in an alternating magnetic field will notonly produce the induced current, but also generate heat. People treat this hate as loss ofenergy and leave no stone unturned to reduce this heat. Late19th century, scientiststruly appreciated the value of its application after the in-depth discussion and researchon the eddy current effect. The theoretical basis of the induction heating was slowlybuilt up. China began to use the induction heating technology in industrial production atearly1950s and began to work on the development of the Medium Frequency PowerSupply at the end of1960s. China’s first Medium Frequency Power Supply was born inZhejiang University, and has been widely used in production. In the1980s, super audiopower (50kW/50kHz) was developed successfully; in the1990s, the current IGBTinduction heating power(50kW/50kHz) and the MOSFET induction heating power(30kW/300kHz) were put into production.With the advent of the thyristor, the modern power electronics began rapiddevelopment with solid-state semiconductor devices as the core. Later, a new type ofshutdown of electronic component, such as the MOS thyristor, insulated gate bipolartransistors (IGBT), static induction transistor, MOSFET field-effect transistors, etc,rised and was widespread used. It set off another a revolution in the field of highfrequency induction heating. At present, Induction heating technology is developingtoward the greater power and the higher frequency field. In the near future, theinduction heating power supply will be computerized, automated and fully equipped.This paper design is small power inverter type induction heating power supply.The working principle of the inverter power supply is to change alternating current of220V to direct current by the means of rectification circuit and filter circuit, then inputto the main circuit of inverter. Under the function of pulse of Control circuit, the fieldeffect transistor MOSFET in the main circuit of inverter conduction or close accordingto the certain frequencies. Then Output must frequency of alternating current. Thisalternating current must be changed by the transformer to suitable voltage and current.Then input to the load circuit. The parameters of induction heating power in this paperis: Output oscillation frequency:=100~250kHz; Output oscillating current: I2=100~200A; Output oscillation power: P2=4KVA; Efficiency: η=80%; Load durationfactor: FSe＝50％; Cooling water requirements:0.2MPa-5L/min.Because the induction heating power supply designed in this thesis has higherfrequency, requires conducting switches frequently, and needs to make the current never turned off, I chose the series resonant inverter structure. The field-effect transistorMOSFET is chosen as a power switching device because its many advantages, such assmaller drive power, faster switching speed, higher operating frequency, better thermalstability and better anti-jamming capability, suitable for smaller power occasions.Calculation according to the given design parameters shows that a pair of ferrite coremodels for the EE55was used for the transformer. Its primary side turns is31, with35diameter of0.41mm enameled wire parallel wound; and its secondary side turns is two,using four parallel hollow brass tubes, whose outer radius is8.69mm while the innerradius is8.03mm. This can avoid the skin effect effectively and reduce the temperatureof the output coil in time. The main circuit includes the buffer starting circuit, the filtercircuit and the MOSFET field effect transistor inverter main circuit. The inductionheating power supply designed in this thesis is low-power, so I chose the single-phasecontrolled rectifier circuit. After processing of filter circuit, the rectified un-smoothvoltage waveform can become a smooth DC with310V voltage that can be supplied forinverter main circuit. It is worth mentioning that the buffer circuit, which can avoid thesurge current producing at the closing moments causing damage to the individualcapacitors in the circuit, is set in the circuit. Turning on the power, the current limitingresistor will be shorted to prevent power loss after the inverter main circuit worksproperly. The buffer time is very short. Three MOSFET taken in the inverter maincircuit are paralleled as a bridge arm switch tube, which can increase the power outputcapacity. At the same time, capacitance and resistance are paralleled at both ends of theswitch in order to avoid the instantaneous voltage is too large to damage it.Control circuit is the heart of the Induction heating power. Its affect is to producepulse providing to the driving circuit, making the field effect transistor MOSFETconduction or close. The pulse is produced by the KA3525of the pulse widthmodulator. In this process, Simultaneous tracking load loop is very important. In orderto prevent load characteristics caused by the resonance frequency drift. In this circuit,current feedback circuit and output power adjustment are necessary. Through changing the pulse frequency to adjust Output power. On the other hand, current transformerreceive current signal to regulate pulse frequency. The most important thing is the maincontrol circuit equipped with dead time in order to avoid shoot through of the fieldeffect transistor MOSFET. There are many protection circuits in the control circuit tomake sure the Induction heating power work stably. Of course, control circuitincludes of power circuit、 start and show circuit to ensure the basic functions of thecircuit.In the last, we perform an experiment to the Induction heating power. During theexperiment,we measured the triggering pulse waveform of KA3525、MOSFET andthe output voltage waveform of transformer under different frequency. Through theanalysis of the waves, proved the power circuits designed in this paper meet to thedesign requirements.更多还原