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Summer maintenance guide for rotomolding machines electrical cabinets
2026-09-03
Major Risks of High Temperature on Electrical Control Cabinets
Rotomolding Machines operate in environments with both oven radiant heat and high summer ambient temperatures. The electrical control cabinet faces the following key risks during summer operation:
| Risk Item | Cause | Consequence |
|---|---|---|
| Excessive cabinet temperature | Combined effect of ambient heat and internal component heat generation; insufficient cooling capacity | VFD derating or tripping; PLC unresponsiveness or abnormal operation; accelerated contactor contact oxidation |
| Cooling fan failure | Clogged filters or insufficient bearing lubrication causing fan jamming | Uncontrolled temperature rise inside the cabinet |
| Moisture condensation | Rapid humidity increase after heavy summer rainfall; temperature differential between inside and outside the cabinet causes condensation | Terminal block creepage; circuit board corrosion; reduced insulation performance |
| Cable joint overheating | Reduced conductor current-carrying capacity in high temperatures; increased contact resistance | Joint melting; phase-to-phase short circuit; potential fire hazard in severe cases |
| Dust accumulation | Increased summer ventilation leads to higher dust ingress | Clogged heat sinks; short circuit risk from dust on circuit boards |
Daily Operating Precautions
Running Checks (Each Shift)
- Monitor cabinet temperature: Cabinet temperature shall not exceed 45°C; cabinets equipped with VFDs or PLCs are recommended to be kept below 40°C.
- Verify that cooling fans and cabinet-top exhaust fans are running normally with no abnormal noise.
- Inspect cabinet door sealing strips for integrity; confirm doors are closed and locked.
- Ensure a minimum clearance of 800 mm is maintained at the front and rear of the cabinet for ventilation; no materials shall be stored nearby.
- After heavy rainfall, open the cabinet door to check for water ingress or condensation marks.
Key Component Inspection
| Component | Inspection Points |
|---|---|
| VFD | Use an infrared thermometer each shift to measure heat sink temperature; heat sink temperature shall not exceed 80°C. If overheating faults occur frequently, shut down the machine to clean the air duct and heat sink. |
| Contactor / Relay | Check for reliable engagement action; listen for continuous buzzing sounds. Contact oxidation accelerates in summer — abnormal sounds typically indicate contact aging risk. |
| PLC / HMI | When ambient temperature exceeds 50°C, some models may become unresponsive or malfunction. Ensure cabinet temperature remains within the component's specified operating range. |
| Switching Power Supply | Electrolytic capacitor life is significantly shortened in high temperatures. Summer is the peak failure period for switching power supply modules — inspect with priority. |
| Wiring Terminals | Focus on high-current circuit terminals including main motor circuits and heating circuits. Check terminals and nearby insulation for discoloration, scorch marks, or burning smell. |
During Shutdown
- For extended shutdowns exceeding 2 hours, disconnect the main power supply.
- During thunderstorms, disconnect the main power supply to prevent lightning surge from entering through power lines and damaging sensitive equipment such as PLCs and VFDs.
- Clean the exterior of the cabinet body to keep ventilation openings unobstructed.
Summer-Specific Maintenance (Recommended Weekly)
Filter Cleaning
Filter cotton at the cabinet air intake is used to block external dust from entering. Maintenance frequency should be increased during summer.
- Remove the filter cotton and use compressed air to blow out accumulated dust from inside to outside. Filter cotton must be completely dry before reinstallation after water washing.
- For heavy dust or oil contamination, soak and clean with a neutral detergent, then dry thoroughly before reinstalling.
- Replace the filter immediately if damage or deformation is found.
Cooling Fan
- After power disconnection, manually rotate the fan blades to check for smooth rotation and any jamming.
- Use dry compressed air to remove dust from fan blades and air ducts.
Electrical Connection Tightening (Must Be Done When Powered Off)
Summer temperature fluctuations cause frequent thermal expansion and contraction, making electrical joints prone to loosening.
| Inspection Location | Tightening Method |
|---|---|
| Main circuit breaker incoming/outgoing terminals | Use a torque wrench to check each terminal individually. |
| Contactor and relay terminals | Use a screwdriver to check and tighten each terminal individually. |
| VFD input/output terminals | Recheck with a torque wrench; also verify shielding layer grounding reliability. |
| Main circuit terminals | This circuit carries high current with elevated thermal stress — prioritize as a key inspection item. |
| Grounding busbar | Confirm all grounding wires are securely connected; grounding busbar surface should be free of oxidation. |
Insulation Testing
- Use a 500V megohmmeter to measure the main circuit insulation resistance to ground; it shall not be less than 1 MΩ.
- In humid environments, prioritize insulation testing of the main circuit to ground.
- If insulation resistance is found to be reduced, disconnect the power and use hot air or an anti-moisture heater for drying treatment.
Temperature Monitoring
Use an infrared thermometer to scan key areas and establish summer temperature baseline data:
- Main circuit breaker terminals
- Contactor terminals and contact areas
- VFD heat sinks
- Heating circuit solid-state relays and contactors
If the temperature difference between phases at the same location exceeds 10°C, shut down the machine and investigate the cause.
Emergency Response
| Symptom | Possible Cause | Response Measure |
|---|---|---|
| VFD frequently displays overheating fault | Clogged air intake, fan failure, or excessive cabinet temperature | Shut down, then clean the filter, heat sink, and air duct; check fan operation status. |
| PLC unresponsive or I/O module error | Cabinet temperature exceeds allowable range | Install temporary fans for forced ventilation cooling; restart the equipment after temperature returns to normal. |
| Main breaker trips | Line overheating causing insulation breakdown, or loose joints causing arcing | Never re-close directly; identify and eliminate the fault point before restoring power. |
| Burning smell or smoke inside cabinet | Overheated joint melting | Immediately disconnect the main power; use CO2 or dry powder fire extinguisher to extinguish the fire. Never use water. |
Recommended Summer Spare Parts List
| Spare Part Name | Recommended Qty. | Purpose |
|---|---|---|
| Filter cotton | 1 set per cabinet model | Replace monthly on schedule |
| Cabinet side cooling fan | 1 unit per model | Fan failure rate is high during hot season |
| Standard contactors / relays | 1 piece each | Quick replacement when contacts are burned |
| Wiring terminals | Assorted | Replace promptly if overheating discoloration is found |
| Desiccant packs | Assorted | Place inside cabinet to absorb moisture |