Electrical Troubleshooting Quiz - December 27, 2016

The plant has several conveyor-based production lines that produce different models of a widget product family. Each line ends in a boxing machine that puts the product in the bar-coded product box. The product boxes then drop onto a conveyor line that takes the output of all these lines to a sorting and crating system. Workers then load the completed crates onto outbound trucks, to fill specific orders. But many times, they are standing around with no product to load because a motor somewhere in this complex system has stopped working.

The repair history shows the digital multimeter (DMM) readings the repair techs took, and nothing indicates a failure cause. What is going on, here?

What’s going on here can be described as “DMM OCD.” Just because the DMM readings don’t indicate a failure cause doesn’t mean the cause is a mystery. The DMM can look at only certain potential problems, such as voltage imbalance. That condition would be a prime suspect in this case, but since it’s not indicated you must look for something else.

For example, use a power analyzer to look at the waveform of the motor supply. And use thermography to check the gearboxes. Poor lubrication practices are typically plant-wide, for the reason they exist in the first place (inadequate training). And they cause motor failure.