The plant has several lines that feed a central palletizer in batch fashion. The reason for this set-up is to run one palletizer full-time rather than run several palletizers only a few hours a day. Of course, when that palletizer goes down, all lines risk overqueing and then stopping.

This palletizer, in fact, goes down more often than expected. The most common reason is because its main motor trips its thermal overloads. An electrician responds to the downtime call usually by going straight to those overloads. A fan is located near the motor, and operators are instructed to use it to cool the motor before the electrician arrives. A 30-minute cooling period seems to be about right.

How might you stop this thermal overloading?

First, ensure the motor housing is clean rather than caked in dust. Confirm there is adequate airflow to and around the motor; boxes or parts trays may be interfering with this. Perhaps use a fan/duct/shroud system to air-cool it.

Next, measure the branch-circuit voltage. Determine whether voltage imbalance is acceptable (e.g., under 2%). Use a power analyzer to identify power quality problems (e.g., flat-topping or low power factor) that may be causing the motor to work harder.

Other steps you may consider taking include:

• Determine whether the thermal overloads are the correct size.
• Change the gearbox oil (use synthetic).
• Check motor alignment.
• Determine if the load at the palletizer is physically jamming in any way.
• Observe operator actions. Is that motor being stopped and restarted?
• Consider upgrading the motor to one with a higher insulation heat rating.