Electrical Troubleshooting Quiz, Oct. 8, 2013

Oct. 8, 2013
Know what to look for when your production line motor overloads blow.

You work in a plant that has implemented a quality control system that lets line workers stop the line for any reason. This principle of fixing a quality problem as early as possible is key in several major quality programs. It should be saving your company money, but unfortunately, restarting the line is problematic.

More often than not, the operator actually disables the system because the motor overloads blow. The plant manager shows you a report signed by the line's maintenance electrician and the system engineer. It states the overloads are correctly sized per the NEC and references 430.32(A)(1).

The plant manager wants you to find the cause and correct it. Where do you begin?

Begin by showing the plant manager 430.32(C). This allows you to amend 430.32(A)(1) by going the next size up. However, the NEC imposes limitations on that, and it may not be a viable solution for the long term because it does mean more heat in the motor. Temporarily, it may be acceptable.

The problem doesn't always occur, which indicates a variable exists. The variable is probably the amount of material on the conveyor. Removing some before a restart might solve the overload problem, especially if you're using larger overloads. But this also is not an optimum solution.

What you want is for the operator to just be able to restart the system and have it run. There may be issues such as voltage drop to solve, so look at those. But the easiest, surest solution is to install a soft start.

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