Three electrical troubleshooting
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l. The jog is normal, but when running at low speed, it will run without running, and there will be an "overcurrent" trip afterwards.
Fault analysis and elimination: After analysis, it is considered that since the jog is normal, it means that the control boards in the power distribution cabinet work normally, while at low speed, they can be operated sometimes, when they are not operational, and there will be “overcurrent” afterwards. Tripping, the analysis may be a problem with its corresponding transmission signal path. Test machine, open low speed operation, the machine does not run, use the multimeter DC voltage file, the output voltage of the speed controller rises up to 2V, and the output voltage of the current regulator has also reached more than 3V, but the phase shift of the latter is measured. The output voltage of the limiter is still inverted (this will not open the car), indicating that the negative input signal of the phase shift limiter controlled by the current regulator is still blocked by the positive signal of the stop commander, so it is initially considered as the stop commander. The low-speed start relay JAJ of the control signal works due to poor normally open contact closure, and the potential of the "output 1" terminal of the stop commander is still "0" with the multimeter DC voltage gauge, which proves that the board is not working. Use the screwdriver to tighten the normally open contact of the relay JAJ to make it close well. At this time, the machine is running and running smoothly, indicating that the fault is here. This can also explain the cause of the "overcurrent" tripping phenomenon: since the other contacts of the relay work well, the input and output signals of the speed regulator and the current regulator are normally increased from zero to a certain value. However, the contact that was not working suddenly suddenly works again for some reason (such as vibration), and the phase shift limiter outputs a large signal due to the unblocking, so that the main motor starts at a high speed and an "overcurrent" trip occurs. After switching to a new intermediate relay, the test machine is repeated and the operation is normal and the fault is eliminated.
2. Start the motor, start the speed is unstable, then stop
Fault analysis and elimination: Observe the electric cabinet voltmeter on the button control box, no index, and judge the fault caused by voltage. When the power is turned off, the control circuit board is unplugged, and the 5-pin and 12-pin solder joints of the integrated operational amplifier are found, and thus the current and voltage cannot enter the operational amplifier and the circuit board does not work. Re-solder these two pins, and then check the pins of other components with tweezers, solder them well, then plug the board back into the original test machine, the motor can rotate, but the speed is still unstable. Using the multimeter DC voltage file to measure the voltage of the integrated 6-pin (output) of the op amp, the jitter is more severe. The voltage at the P3 point (input) is also jittered. It is presumed that the output is unstable due to input instability, which may be C6 filtering. The capacity of the capacitor is reduced or invalid. However, after the power is cut off, the control circuit board is pulled out, and a pin of the C6 capacitor is soldered with a soldering iron, and the charging and discharging performances are normal, and there is no leakage phenomenon. After further analysis of the schematic diagram, it is considered that if the circuit of the latter stage of the op amp is unstable, it can directly lead to the instability of the motor speed, and at the same time, through the feedback loop, this unstable signal will be added to the input end. After the internal amplification of the op amp, the output is more unstable, which is the reason why the voltage at the input terminal of the front is not stable. Therefore, use the multimeter resistance file to detect the resistance between the pins of each component, and whether the connection between each pin and its own solder joint is normal, and then make further analysis and judgment. From the amplification tubes BGl, BG2, BG3, ... and their associated resistors and capacitors, it was found that there was a problem in the resistance between the pins of the amplifier tube BG3, and the resistance between the base solder joint and the emitter solder joint was over. Large (300kΩ), and the resistance between the base solder joint and the collector solder joint is normal (300Ω). The resistance of the two groups should be basically the same when it is normal. It is judged that the emitter pin is poorly soldered and is positive. The normal resistance (300 Ω) between the base and emitter pins was confirmed, and the pin did not loosen. One of the uses of the amplifier tube BG3 is to provide a stable operating voltage to the collector of the BG2. Therefore, when the tube is in poor operation, the pulse frequency of the single junction transistor is unstable (the signal is taken from the amplifier tube BG2, the collector voltage), thereby causing the main circuit operating voltage to be unstable and the motor speed to be unstable. After the soldering of the pin is loosened, the oxide layer on the electrode is scraped off and re-soldered, and the motor is re-tested. The rotation speed of the motor is stable, and the test machine is normal and the fault is eliminated.
3. Stop, ring the bell, and the machine will run by itself without pressing the button. Sometimes the machine does not work, but you can hear the current sound in the main motor, but at this time, it is jog or low speed, the machine does not run.
Fault analysis and elimination: From the analysis of the phenomenon, the possibility of failure of the control circuit is greater. Because if the main circuit is faulty, the machine will run by itself after each ringing. Closing, ringing, the machine is not running, but you can hear the current in the main motor. First use the multimeter DC voltage file to measure the current regulator and phase shift limiter, all have a voltage output of ±10V, which means that the machine is in the high-speed signal state although it has not rotated. Re-measuring the given integrator also has 1V voltage input and output, which means that although there is no power on, there is already a signal input in the given integrator. Open the power distribution cabinet and find that the low-speed start relay JAJ is working. In addition, the small motor in the given part of the motor does not drive the given potentiometer completely to zero. Therefore, the cause of the failure is as follows:
3.1The machine has a current sound but does not work. After the shutdown, the small motor does not automatically reverse to the zero position, so that the main AC contactor control circuit is disconnected and cannot be closed when the switch is closed again. There is no working voltage on the main circuit of the thyristor, so that the motor cannot run. Because the JAJ contact of the relay is not released, and the control board of each stage has signal input and output, the main motor does not rotate, but each thyristor is triggered by the rotation to generate micro leakage current, resulting in current sound.
3.2 After you ring the bell, you will run by yourself. Because the relay JAJ is not released, and the small motor is in good contact with the line (not reversed to zero position), the working voltage is generated on the main circuit of the thyristor, and the signal is triggered to make the machine run by itself. When the gate is closed, the relay JAJ is first removed and checked, and its internal movement is found. There is a layer of sludge on the pole surface of the static iron core. This is the reason why the contact coil can not be released when the working coil is de-energized. Therefore, wipe it with a rag and rub it and reinstall it. Then check the failure of the small motor to reverse the position after the stop, open the "given and magnetic field" drawer, turn the rotor shaft of the small motor by hand, and do not find the phenomenon of jamming or rotating resistance, indicating the reason of the circuit. To check the normally closed contact wiring of the speed increase relay 2KJ, it was found that one of the wires was loose, the screw was not tightened, and it was found that there was an oxide layer on the wire end. After scraping the oxide layer with an electric pen, reinstall it, and then close the test machine. The small motor immediately reverses to zero position. Press jog, low speed, speed increase, deceleration, etc., everything is normal, and the test machine is repeated, all running normally, troubleshooting.
4. During start-up, the surface temperature of the oil pump is higher; the oil pressure is stable at 0.5 (if the oil is put down manually, the pressure will drop to a higher value of 0.6); the oil is not “lubricated”.
Fault analysis and elimination: the surface temperature of the oil pump is high during startup, because the oil pressure is set too high (0.6), so that the oiling time is too long; and because the oil in the pump does not come out, the new oil does not come in, and the pump The body does not get circulation cooling, so it gets hotter. After adjusting the pressure regulating nut (hexagonal type) on the pressure relay counterclockwise, the oil pressure is reduced to 0.32, and the oil is manually put down. When the oil pressure drops, it rises to 0.4; and after that, the oil pressure is automatically increased to 0.4. Drain the oil (lubricate the machine), continue to oil after the oil pressure drops... so cycle back and forth. In the afternoon, I went to touch the surface of the oil pump, and the temperature has dropped drastically.
—— Only a little warm, just back to normal.
5. The surface temperature of the oil pump is too high, and the index in the oil pressure gauge is 0.3, and the oil is not “lubricated”.
Fault analysis and elimination: According to the analysis of this situation, the cause of the fault is still that the oil is not drained (causing the oil in the pump to not flow out, cooling and the pressure is not enough). In order to confirm this, the valve core of the solenoid valve is lubricated by the screwdriver, and the oil is lubricated by hand. At this time, it can be seen that the oil pressure rises and rises above the original value; after repeatedly pressing the lubrication solenoid valve, the oil pressure is actually pressed. It can be raised to 0.4 or more, thereby confirming that the oil pressure rise is not high and the surface temperature of the oil pump is too high because the machine cannot automatically perform oil discharge lubrication. To make the machine automatically drain and lubricate under a certain pressure, first make sure that the pressure relay works normally, so that the signal voltage can be sent through it (through the AC contactor in the power distribution cabinet) to make the lubrication solenoid valve work (discharge ). Hand touch the head of the limit switch in the pressure relay, and use the electric pen to measure the power at the fire point. Measure the output point without electricity, indicating that the limit switch is damaged, thus causing the signal voltage not to be sent to the latter stage. The failure of the circuit works. After switching to a new limit switch, the test machine: the oil pressure recovery reached 0.4, the action of the oil circuit hitting and releasing the oil returned to normal, and the temperature of the surface of the oil pump gradually decreased.