Membrane welding machine
is the electromechanical system used to realize high frequency welding. The membrane welding machine is composed of high frequency welding machine and tube welding machine. Membrane welding machine is generally composed of two parts: high frequency generator and feeding device. Its role is to generate high frequency current and control it; the forming machine consists of an extruding roller stand. Its function is to squeeze the part that is melted by the high-frequency current.
1. High-frequency generator: in the past, the high frequency generator used on the welded pipe unit was three-loop and it's basically been improved to a single loop later. There are many methods to adjust the output power of high frequency oscillator, such as autotransformer, reactance method, thyristor method and so on.
2. Feeding device: it is used to transmit high frequency current to the tube, including electrode contacts, induction coil and impedance. In general, in the contact welding, the electrode contact of wear-resisting copper-tungsten alloy is adopted, and the induction welding adopts the induction ring made of red copper. The main component of the impedance is the magnetic core, which is used to increase the inductive reactance on the surface of the pipe to reduce the invalid current and improve the welding speed. Impedance device adopts ferrite core, and it requests the Curie point temperature should be not lower than 310 ℃. Curie point temperature is an important indicator of the magnetic core. The higher the Curie point temperature is, the closer it will be to the weld, and the closer it is, the higher the welding efficiency will be.
3. The frequency control system is designed to make the triode always work at the resonance frequency of the system. The resonant frequency is determined by measuring the frequency of the output current. This frequency is then used as the time base signal to activate the transistor. The transistor driver card sends a signal to each transistor on each inverter module to control when the transistor is turned on and off.
4. The output power control of the induction heating system is controlled by the output current of the inverter. The above control is accomplished by a power control card used to control the triode driver.
5. The reference value of output power is given by the power reference potentiometer on the IMC control panel or it is output from the external control panel to the control system. After this value is transmitted to the system controller, it will be compared with the DC power value measured by the rectifier unit measurement system. The controller includes a qualification function that calculates a new output current setting based on the comparison of the reference power value with the DC power measurement value. The output power set value calculated by the controller is sent to the power control card, which will define the output current according to the new set value.