First, the working principle and control process 1. The circuit composition and component function of each department The drawing is a schematic electrical diagram of a KSW-3 type temperature automatic controller. The triode BG1, the coils L1, L2, and L3 and the capacitors C1, C2, C3, C5, and C8 in the figure constitute a high-frequency inductance three-point oscillation circuit. The oscillation signal is output via D1 detection. BG2, R6 and R7, relay J and other components form a DC amplifier circuit. The AC contactor CJ completes the power control of the high temperature electric furnace. The power transformer B, in addition to the temperature conversion circuit and the red and green indicator lights to provide AC low voltage, also outputs a DC voltage of 12V through the D3 and D4 as the power supply of the oscillation circuit and the amplifying circuit. The current meter A is connected in series to the power supply of the high-temperature furnace, and the indicators XD1 and XD2 together show the energization and power-off of the high-temperature furnace. The temperature conversion circuit consists of thermocouples R and R9 ~ R13, C9. Connect the D5 across the thermocouple to prevent thermocouple disconnection. The meter is damaged due to excessive current. Another resonant circuit composed of the oscillation coils L3 and C8 and a millivolt meter constitute the indicating control section. 2. Working principle and control process After the power is turned on, the oscillator and the amplifier start working. The oscillation signal is output by the BGl emitter. After the detection of D1, BG2 is turned on, the relay J is held, the AC contactor CJ is pulled, and the high temperature furnace starts to heat up. The temperature inside the furnace is converted into an electric signal (electromotive force) by a thermocouple and transferred to a moving-type millivoltmeter so that the pointer with the aluminum plate is deflected to the right. When the pointer enters the gap of the oscillation coil L3 (predetermined temperature). Due to the high-frequency eddy current effect on the aluminum sheet, the total inductance of L3 is greatly reduced, resulting in an increase in the current impedance of the resonant loop of L3 and C8 to the oscillation frequency. The oscillation amplitude decreases and even stops. At this time, the base signal that is output to BG2 after detection by D1 is greatly weakened, and BG2 is turned off, and the contact of relay J is released. The AC contactor CJ opens. The contact is released. Cut off the power of the high-temperature furnace, and the high-temperature furnace stops heating. As the furnace temperature gradually decreases, the electromotive force of the thermocouple R also weakens, causing the millivoltmeter hand to deflect to the left. When the pointer exits the gap of the oscillation coil L3, the circuit resumes oscillation. BG2 is on, J is on hold, CJ's power is on, contacts are closed, and the high temperature furnace starts to warm again. By repeating this action, the furnace temperature is maintained within a predetermined range, and automatic temperature control is achieved. Second, troubleshooting 1. Visual inspection and judgment (1) Judgment: The XDl (red) and XD2 (green) indicators on the control panel respectively indicate the heat preservation and heating of the high-temperature furnace (ie, power off and power on). Close the K2 under normal conditions; the oscillation and amplification circuit starts to work, and the relay J holds, turns on the green light, and then turns on the K1, CJ action, and the contact pulls in. If the green light is off, the red light is on. And there is no indication of the current meter, CJ no action noise. It can be judged that the AC/DC circuit and temperature conversion circuit of the power supply part work normally, and the fault may occur in the circuit of oscillation, detection and amplification; if the power is turned on, the high-temperature furnace can be heated, but when the millivoltmeter pointer is deflected to a predetermined temperature, The green light is not off, and the red light is off. If the high-temperature furnace continues to heat, that is, if the control fails, it can be determined that the three parts of the AC/DC circuit, the temperature conversion, and the detection of the power supply part are normal, and the oscillation and amplification of these two parts may fail. (2) Inspection: Remove the casing and carefully inspect the components such as relays, AC contactors, transformers, etc., for obvious burn marks, and whether the terminals, circuit connecting wires, and components are disconnected or unwelded. Then turn on the power. The above components were tested in turn using a pencil. The input and output terminals of the connection wire have electricity. 2. Voltage detection After the above-mentioned inspection, if the fault is still not detected and eliminated, you need to use the DC voltage block of the multimeter to measure the voltage of each pole of the triodes BG1 and BG2. Should comply with the values ​​listed in the schedule. Hydraulic Pipe Bender,Hydraulic Bender Machine,Hydraulic Tube Bending Machine,Manual Hydraulic Pipe Bender Taizhou Juhuan Lifting Protection Equipment Co., Ltd , https://www.jsjoba.com