SP series includes SP-04C、SP-15、SP-25、SP-25BD、SP-35B、SP-45B and  SP-70B with frequency from 30 to 80KHZ， these machines are our earliest models and have been used most widely now because of their simplicity and low price.  Especially the SP-04C and SP-15 model.
Their main application covers blade brazing, copper parts brazing, small part heat treatment and so on.
1、  Working theory and structure
In these machines, series oscillating circuit is applied, through high frequency transformer, low voltage and high current power is output to go through the induction coil. 

SP-04C, SP-15 and SP-25 series machines are the first models developed in our company, using MOSFET and IGBT components and our first generation inverting control technology,  the machines are featured with simple structure, high reliability and low price, and they are easy to use and to repair, and are now the most widely used machines both in China and abroad.

 
In SP-25BD, SP-35B and SP-45B series machines, IGBT module and our second generation inverting control technology has been used, that is the dual control and inverting technology. In these new technologies, output power and oscillating frequency are controlled independently. we use IGBT components and high frequency voltage regulate control circuit to control the power and we use IGBT components, series oscillating and automatic tracing circuit to reach  soft switching in the inverting course, all these make the machine to be more reliable and make the machine possible to work continuously with 100% duty cycle. 
Compared to machines with first generation technology, second generation technology is more suitable for large power machines to get higher reliability.
Due to the adopting of advanced technology, SP-25BD, SP-35B and SP-45B series machines are characterized by larger frequency range, smaller size, water cooled transformer, higher reliability and lower repair cost.


 
Inside SP-70B  series machines, IGBT module and our third generation inverting control technology has been used, that is the soft and dual control and inverting technology. In this technology, output power and frequency can be controlled and adjusted separately, IGBT module and soft switching control technology are used in the high frequency switching circuit to control the output power.  In the inverting circuit, the IGBT and frequency tracing circuit is applied to achieve high speed and accurate soft switching control. The adoption of new technologies not only improves the quality and reliability of the machine，but also solve the technology problem on large power induction heating machine and makes it possible to work 100% duty cycle.


 

2、 SP models meaning


 
3、 Main models in SP series
SP-04C series ：SP-04C、SP-04AC；
SP-15 series ： SP-15、SP-15A、SP-15B、SP-15AB；
SP-25 series ： SP-25、SP-25A、SP-25B、SP-25AB；
SP-25D series：SP-25D、SP-25AD、SP-25BD、SP-25ABD；
SP-35B series：  SP-35B、SP-35AB；
SP-45B series：  SP-45B、SP-45AB
SP-70B series：SP-70B、SP-70AB