Burnout failure analysis of stepper motor driver

Once started, the external fuse of a stepper motor driver will be burnt out and the device can not operate. When finding that a power tube is damaged during the inspection, the maintenance worker doesn’t know the function of the tube due to lack of related information and replace with a new power tube. But the fuse is burnt out again and the new tube is also damaged. After inspection, the maintenance engineer obtains the correct initial analysis, that is, repeatedly burnout fuse means certain abnormal high current exists in the driver and a damaged power tube. But the engineer doesn’t figure out the role of the tube. In fact, the tube is a power drive tube of the stepper motor. The stepper motor stats at high voltage, so it has to withstand high voltage and high current. The maintenance engineer conducts static check and finds that the resistance between the power supply of pulse ring distributor line and the ground terminal, but there is no short circuit. But the resistance should not be small based on the analysis of the number of components in the line and its power consumption. Therefore, the engineer suspects that some components are damaged.

The maintenance engineer finds a chip with abnormal heat though power-on check. Turn off the power, cut off the chip’s power supply pins, and conduct static check. It’s normal that the resistance between the power supply and the ground increases, and the resistance between the chip power supply and the ground is very small. Check the model of the chip, and find it is a non-standard model and can not be found in many manuals. Through line analysis, it is confirmed that the chip is the main component of the board: ring pulse distributor.

Troubleshooting steps of burnout stepper motor driver:

To further confirm the problem of the chip, first change with a new stepper motor power driver tube with equivalent withstand voltage current power, restore the power supply pins of the chip, and replace stepper motor windings with LED circuit for analog load. After powered on, the LEDs are lightened, that is, the windings are energized, which is not in line with the requirements of the line. There’s no response after inputting stepping pulse, so the chip is confirmed to have been damaged. But the chip is not available on the market. If the housing space of stepper motor driver permits, a ring pulse distributor is designed through combination of lines, i.e., combining the existing D-type flip flop with non-gate, and made in a small printed board. Remove the original chip, and install the small printed board on the pad of the original chip through the pins. Perform analog load by using LED, add stepping pulses after powered on. Remove the analog load and then power on, and the device operates normally.