Step 1: First, check for basic common issues and eliminate simple faults.
These types of faults account for over 60% of electrical faults and can be resolved quickly by prioritizing them:
1. Check the power supply and wiring: Observe all power indicator lights. If the indicator lights are not lit, directly check if the main circuit breaker has tripped and if the incoming line is loose or overloaded. If the device reports an undervoltage fault, measure the incoming line voltage to check for poor contact.
2. Check the appearance and environment: Open the electrical control cabinet and check for blackened, discolored, or burnt components, and whether the cooling fan is stopped. If there is a lot of dust, clean the inside of the cabinet and the filter first. In humid environments, check for reduced insulation.
3. Check fasteners and wiring: Shake the contactor and relay terminals to check for looseness. Looseness will directly cause poor contact and tripping. Step 2: Quickly Locate Specific Faults Based on Fault Symptoms
After troubleshooting basic issues, directly pinpoint the specific fault based on its symptoms:
1. Equipment completely unable to start/Does not reset after emergency stop
First check if the emergency stop button is pressed and if the emergency stop circuit is disconnected. Next, check if the limit switches on the safety guard are in position. These are normal shutdowns triggered by safety protection and are not hardware failures.
If the safety circuit is normal, check if the PLC's running indicator lights are normal to rule out PLC crashes (a power cycle will resolve this).
2. Motor-related faults (armature overvoltage/overcurrent/not rotating)
First disconnect the motor load and restart the DC unit:
If the fault persists after disconnecting the load → the DC unit itself is hardware damaged and requires professional replacement; do not disassemble it yourself.
If the fault disappears after disconnecting the load → rule out mechanical jamming (e.g., bearing seizure). If the mechanical components are normal, the motor power is insufficient or the windings are short-circuited, requiring motor repair.
For armature overvoltage, first check: Is the paper feed roller's acceleration/deceleration time too short? Increasing the parameters will resolve the issue. Next, check if the encoder (speed feedback) wiring is loose or open.
3. Communication Failure (Bus Connection Abnormality, Equipment Unresponsive)
First, check the communication parameters: Whether the station number and baud rate settings match the system. Incorrect parameters are the most common cause.
Next, check the terminal resistance: Measure the resistance value at the end. If the resistance deviates from the nominal value, replace it directly to rule out signal reflection issues. Finally, check whether the communication cable is mixed with the power cable; separating them will eliminate interference.
4. Unstable Tension/Speed
First, observe whether the tension value on the touchscreen fluctuates greatly. If the fluctuation is abnormal, directly check the tension sensor wiring and power supply to rule out sensor malfunction.
If the value is stable but the actual tension fluctuates, check whether the hydraulic system pressure of the paper pressure roller is normal and whether the parameter curve is set incorrectly.
Step Three: Safety Precautions
1. When performing maintenance after power failure, wait until the capacitor in the electrical control cabinet has completely discharged (indicator light goes out, voltage drops below 30V) before operating to prevent electric shock.
2. After the DC device is damaged, do not attempt to power it on for testing. Professional personnel must perform the repair to avoid further damage.
