Fault phenomenon: Once started, the external fuse of the driver is burned out, and the equipment cannot run. When the maintenance personnel inspected, they found that a power tube was damaged, but because there was no information, they could not figure out the function of the tube, thinking it was the front push of the power drive. , replaced a power tube, after the power was turned on, the insurance was burned again, and the replaced tube was also damaged.
After detailed inspection by the maintenance personnel, the initial analysis was correct, that is, the fuse was repeatedly blown, there must be an abnormal high current in the driver, and a power tube was found to be damaged, but the function of the tube was not clear. In fact, the tube is a stepper motor power drive tube, and the stepper motor is started at high voltage, so it has to withstand high voltage and large current. The static inspection of Shenyang No. 1 Machine Tool Factory found that in the circuit of the pulse ring distributor, the resistance value from the power supply to the ground terminal is very small, but there is no short circuit. According to the number of components in the line and its power consumption analysis, the resistance value from the power supply to the ground terminal should not be so small, so it is suspected that there are components in the line damaged.
After power-on inspection, it is found that a chip is abnormally hot; after power-off, the power supply pin of the chip is disconnected, and static inspection, the increase of the resistance value of the power supply to the ground should be normal. Shenyang No. 1 Machine Tool Factory measured the resistance of the chip’s power supply to ground is very small. The machine tool factory checked the Model of the chip, and it was a non-standard model, which was not found in many manuals. After circuit analysis, it was confirmed that it was the main component (ring pulse distributor) in the board.
In order to further confirm the problem of the chip, the machine tool factory first replaced the stepper motor power drive tube with the same withstand voltage and current power, restored the power supply pins of the chip, and replaced each winding of the stepper motor with a light-emitting diode circuit as a simulated load. After the machine tool factory is powered on, the light-emitting diodes are all on, and the machine tool factory is powered on all windings, which does not meet the circuit requirements, and there is no response to the input stepping pulse, so it is confirmed that the chip is damaged.
This chip is not available in the market. When the space in the driver housing allows, a combination circuit is used, that is, a ring pulse generator is designed with the combination of the existing D flip-flop and NAND gate, and is fabricated on a small printed circuit board. On the board, remove the original chip and install the small printed board on the pad of the original chip through the pins, and still use the light-emitting diode as a simulated load.
The machine tool factory removed the simulated load, connected to the host, powered on, and the equipment was running normally. The example of the machine tool factory shows that the maintenance personnel should not only be able to analyze the phenomenon (overcurrent) and find out the obvious cause of the failure (damage of the power tube), but also be able to analyze the primary cause of the failure step by step (damage of the pulse generator), And can use the existing component combination to replace the difficult-to-solve device problem.
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