A paper cup machine motor cooling fan can be obstructed or damaged while the motor still turns normally. Repeated temperature alarms therefore need an airflow investigation as well as a current and load check. Raising a protection setting does not restore cooling and can hide a developing fault.
First identify whether the motor is self-ventilated, separately ventilated or uses another cooling arrangement. This guide applies to accessible external fan and airflow checks. It does not authorize opening energized equipment, changing protection limits or operating without the fan guard.
Diagnostic decision table
| Observation | Question | Evidence |
|---|---|---|
| Alarm after extended low-speed operation | Does cooling depend on shaft speed? | Motor cooling type and duty record |
| Debris on fan guard | Is intake or discharge obstructed? | Photographs before cleaning |
| Fan turns but airflow seems wrong | Is the fan damaged or incorrect? | Part identity and approved direction |
| Temperature remains high after cleaning | Is load or electrical condition abnormal? | Current, speed and temperature trend |
Define which temperature is being reported
Record whether the alarm comes from a winding sensor, a drive thermal model or an external temperature measurement. These readings describe different things. Save the exact alarm text, elapsed running time, commanded speed, load condition and nearby ambient temperature.
Do not compare a housing surface reading directly with a winding protection threshold. Use the same measurement location and instrument for repeat observations. A useful record distinguishes a sudden change from a gradual rise and notes whether the event followed a material change, slower production setting or recent motor service.
Check the complete cooling path under isolation
Stop and isolate all relevant supplies, including any separately powered fan. Allow safe cooling before removing a cover through the documented maintenance process. Inspect the inlet grille, fan blades, housing fins and the intended exit route. Paper debris behind a grille can be missed by a quick external wipe.
Check nearby cartons, wall clearances and added covers that may restrict air movement. Use the approved cleaning method without forcing debris into electrical openings or bearings. Restore damaged guards and retain photographs of unusual deposits, because repeated buildup may require a housekeeping or extraction review.
Confirm fan identity and mechanical condition
Compare the fan and guard with the motor parts list. Inspect for cracked blades, rubbing, loose attachment and the wrong replacement profile. A fan that physically fits the shaft is not automatically suitable for the motor cooling arrangement. Do not reshape blades to stop contact.
Where a separate blower is installed, have qualified personnel verify its supply and control state using the electrical documentation. Check whether it is intended to operate before, during or after production. Never assume that the main motor running proves the independent blower is powered or moving air in the required direction.
Review low-speed duty without guessing a limit
For shaft-driven fans, cooling capability can change with motor speed. SEW-EURODRIVE documentation distinguishes self-ventilated motors from forced-cooling options and identifies reduced fan cooling at lower speed. The applicable operating envelope still belongs to the exact motor and drive combination.
Compare the current production duty with that envelope, including long low-speed runs and repeated starts. Ask the supplier to evaluate a proposed blower or duty change; adding an improvised fan is not a validated motor upgrade. Also check mechanical load and drive settings so airflow is not blamed for an unrelated overload.
Release with a comparable thermal trend
After approved repairs, restore guards and repeat a representative operating condition. Record speed, product load, current, ambient temperature and the original temperature indication over the agreed observation period. Stop if the alarm returns or the trend is inconsistent with the approved limits.
Keep protection settings unchanged unless an authorized engineering review has approved a correction. Send HANNAI the motor label, cooling arrangement, before-and-after photographs and trend. The decision should identify whether ventilation maintenance solved the problem or whether motor sizing, drive configuration or mechanical loading still requires investigation.
Related equipment and next checks
Review the HN-M100 forming equipment and the related guide to VFD and motor drive diagnosis. The Engineering Notes archive connects these checks with wider machine planning.
Technical reference
- SEW-EURODRIVE motor cooling and forced ventilation options — general reference; confirm applicability to the installed equipment.
Frequently asked questions
Does a rotating motor prove that its cooling fan works?
No. Inspect the actual fan arrangement and airflow path.
Can the thermal trip setting simply be increased?
No. Diagnose the cause and preserve approved protection.
Is a surface temperature the same as winding temperature?
No. Identify the source and meaning of each reading.
Can low-speed production affect cooling?
It can on self-ventilated motors; confirm the permitted duty.
Review the evidence with HANNAI
Send your machine model, component identification and the observations described in this guide. Include the drawing or material reference and any before-and-after measurements so the required next check can be identified.