Characteristics and development trend of induction heating
Before the development of induction heating technology, resistance furnace, gas combustion furnace and fuel furnace are the main methods of heating metal and non metal. Induction heating has the following advantages compared with it:
Characteristics of induction heating
- Rapid heating: the heating of workpiece by induction heating is faster than that of convective and thermal radiation heating by conventional heating.
- The oxidation loss is small: compared with the slow heating process of the gas combustion furnace, rapid heating greatly reduces the material's oxidation loss.
- Quick start: the conventional heating furnace contains a lot of refractory materials, which must be heated to a certain temperature when starting, so that it can start and cause greater thermal inertia. Induction heating, through heating the interior of the workpiece, generates heat from the inside, which greatly avoids the problem and accelerates the starting process.
- Energy saving: when it is not used, the induction heating power can stop running at any time because of its fast starting performance, and the traditional heating mode must provide continuous heat to ensure that the whole heating process is not delayed, while avoiding a long starting time.
- The production efficiency is high: because heating time is short, induction heating usually can continuously improve production efficiency and reduce labor cost.
- High degree of automation: due to the good controllability of induction heating, it is easy to realize the automation and intelligence of the whole line.
The development trend of induction heating
Due to the continuous progress of power semiconductor devices and the improvement of automatic control, induction heating power is developing in the following aspects.
The field of application is becoming more and more extensive
With the wide application of power semiconductor devices such as MOSFET, electronic tube power has been phased out in the field of high frequency (over 100kHz), which is replaced by all solid state high frequency induction heating power supply using power semiconductor devices. For the medium frequency / super audio field, the IGBT solid-state power source has been greatly applied to replace the crystal gradually. The application field of sluice solid state power supply is becoming more and more widely used. For low frequency domain, low cost and large capacity SCR power supply has completely replaced the original medium frequency generator, and it has become the first choice of induction heating power in this field.
At present, the capacity of the induction heating power supply is expanded by adopting the series, parallel or multi bridge series, parallel connection and corresponding control strategies of power semiconductor devices, which makes its application wider.
Small, clean and green pollution of the power grid
For the medium and small power induction heating power supply, the PWM control strategy or PFC technology can be used on the rectifier side, which can realize the unit power factor operation on the net side, improve the system efficiency and achieve zero pollution to the power grid. For the high-power induction heating power supply, the rectifier side can use the three-phase 12 pulse rectifying to reduce the harmonic current on the net side. .
Load matching technology
For induction heating power, inverter circuit and load is a unified whole, so load matching is a very important problem. The efficiency, utilization and reliability of the power supply will drop sharply when the inverter and the load are not properly matched because of the different applications and many kinds of load. At present, the main matching methods are electromagnetic coupling (series induction heating power) and electrostatic coupling (parallel induction heating power) two. Due to the full control characteristic of the load energy, the series induction heating is more easy to realize the load matching technology on the inverter side, and the inverse load matching method is numerous, but each has its advantages and disadvantages. It is of great significance to study a high efficient and controllable inverter matching technology.
Improve the level of automation for the whole machine
With the development of intelligent technology such as computer and digital signal processing, the induction heating power not only increases the self protection function, but also has a strong readable man-machine interface, and the induction heating power is developing towards the direction of digitalization, automation and self energy.