A heat-sink overheat trip means the drive’s thermal protection has detected a temperature above its safe threshold. Repeated resets may restart a cooled drive, but they do not correct restricted airflow, excessive losses, high cabinet temperature, overload, or a bad temperature-sensor signal. Record the operating conditions, restore cooling, and prove the drive can carry the process load without another trip.
Stop the quick fixes that hide the cause
Do not start by increasing protection limits, repeatedly resetting the fault, or aiming a temporary fan at a closed cabinet. A reset works only because the heat sink cools while production is stopped. The fault returns when the same heat input and cooling restriction return.
| Observed pattern | Likely area to check | Wrong first response |
|---|---|---|
| Trip returns faster after each reset | Cooling capacity is falling or the drive remains heavily loaded | Continue resetting |
| Trip appears during high-load operation | Motor current, drive sizing, or acceleration/load demand | Replace the fan without checking current |
| Trip occurs in a hot enclosure | Ambient temperature and enclosure heat removal | Clean only the drive exterior |
| Trip occurs when the heat sink is not unusually hot | Temperature sensor, sensor mounting, or sensing circuit | Assume the power section is overheating |
Before changing anything, capture the displayed fault, motor current, process load, cabinet temperature, fan operation, and time from start to trip. Check: the initial record must be complete enough to reproduce the operating condition.
Isolate the drive and inspect the cooling path
- Stop the process using the normal operating sequence.
- Isolate electrical power under the site’s approved procedure and wait for the drive’s stored-energy indication to show a safe condition.
- Inspect the air inlet, outlet, filters, fan openings, heat sink, and the clearance around the drive.
- Look for dust mats, blocked louvers, damaged ducting, nearby heat sources, loose debris, and components installed too close to the ventilation path.
Cooling depends on air entering, crossing the heat-transfer surfaces, and leaving without being recirculated. An open cabinet door can temporarily reduce temperature while concealing a blocked filter or inadequate enclosure cooling.
Stop here if there is heat damage, melted insulation, a burnt smell, a damaged fan, loose power conductors, or contamination that cannot be removed without dismantling the power section. Check: identify a clear inlet-to-outlet airflow path before moving to cleaning or fan tests.
Restore airflow and prove fan operation
- Remove obstructions from the drive vents and cabinet airflow path.
- Clean or replace dirty air filters.
- Clean the fan and heat sink with a soft brush or controlled compressed air, following the Delta manual for the installed model.
- Prevent loosened contamination from being driven deeper into the electronics. Do not force the cooling fan to overspeed with compressed air.
- With guards restored and conditions safe for operation, run the drive and confirm that each cooling fan starts and maintains normal speed.
A fan that turns by hand can still fail under power, start intermittently, or run too slowly to move the required air. Noise, vibration, delayed starting, and weak discharge airflow point to a worn or obstructed fan. Replace a failed or slow fan with the correct service part for the installed drive; do not substitute a fan based only on physical size.
Check: verify steady airflow through clean filters and across the heat sink, with all covers and guards in their normal operating positions.
Measure cabinet temperature and operating load
Measure temperature at the drive’s cooling-air inlet while the enclosure is closed and the process is running. The working range cited for this fault class is typically 0°C to 40°C, but the installed model’s Delta manual and its derating information control the decision. Temperature outside the permitted range calls for better enclosure ventilation, external cooling, reduced internal heat load, or relocation.
Next, record drive output current through a full production cycle. Compare it with the drive rating, motor data, and the application’s continuous and peak demand. A drive operating near maximum capacity for long periods creates more power-device loss, including loss in the IGBT module, than a lightly loaded drive.
- Run the least demanding production condition first.
- Record inlet temperature and output current after conditions stabilize.
- Increase to the normal process load while watching current and temperature.
- If the trip follows load, reduce the motor load and repeat the test.
If reducing load prevents the trip, inspect the driven machine for excess mechanical demand and review whether the drive is undersized. Check: confirm that inlet temperature and current remain inside the limits published for the exact drive, installation, and operating mode.
Review switching frequency and drive sizing
Higher switching frequency generally increases switching losses in the power devices. That heat must pass through the heat sink and cooling air. Do not enter an arbitrary lower value: read the configured switching-frequency setting, then compare it with the Delta manual’s recommendation for the specific drive model, motor size, cable arrangement, and application.
- Back up or record the current drive configuration.
- Find the switching-frequency setting in the installed model’s parameter list.
- Compare the setting with the manufacturer’s permitted range and derating requirements.
- If the setting is above the suitable value for the application, reduce it within the published range.
- Run the motor and check current, heating, acoustic effects, and process performance.
Changing switching frequency cannot compensate for blocked airflow, a failed fan, excessive ambient temperature, or an undersized drive. If normal load repeatedly pushes the drive to its rating or thermal limit, select a drive with adequate continuous and overload capacity after verifying the motor and application requirements.
Check: run the original load with the corrected setting and confirm that temperature remains stable without sacrificing required motor control.
Test the temperature signal and complete the run
Investigate the heat-sink temperature sensor only after airflow, ambient temperature, current, switching frequency, and sizing pass their checks. A faulty or misaligned sensor can report an overtemperature condition even when the heat sink is not excessively hot.
- Compare the drive’s reported temperature, if available, with an independent measurement taken at a repeatable accessible point.
- Inspect accessible sensor connections and mounting without opening or probing the energized power section.
- Check for an abrupt or implausible temperature change at the moment of the trip.
- Realign or replace the sensor only under the service procedure for the exact model.
- Reassemble the drive, restore normal cabinet cooling, and run a complete production cycle at normal load.
Log inlet temperature, current, fan operation, switching-frequency setting, load, and whether the fault returns. The final proof is a full cycle with the cabinet closed, normal ventilation active, and the machine carrying its required load.
FAQ
Why does a drive heat-sink overheat fault return after reset?
The stopped drive cools enough to reset, but the blocked airflow, failed fan, high ambient temperature, excessive current, or high switching loss remains. Record how quickly the fault returns and check cooling and load before resetting again.
Why does lowering the motor load stop the overheat trip?
Lower current reduces losses in the drive’s power section and IGBT module. Check for excess mechanical load and compare the application demand with the exact drive rating before deciding that a larger drive is required.
Why does the drive trip when the heat sink does not feel hot?
A misaligned or faulty heat-sink temperature sensor may create a false trip, but test airflow, ambient temperature, current, and switching frequency first. Stop and contact official Delta support if the temperature indication is implausible, the sensor is inside the power section, the trip persists after all external checks, or there is visible heat damage; provide the exact drive model, displayed fault, configuration, current, temperature measurements, and test results.