Circuit Breakers, Motor Overloads and Lighting
I thought I’d put up a post about things that I see in my day to day life as a maintenance electrician, I hope you enjoy it.
Today was a pretty crazy day at work. It started out with me being called to investigate some heater elements in an oven at the end of a conveyor line. There were 4 elements out in a row, so this told me it was not just something wrong with the individual elements, it was more likely a circuit breaker had tripped or a fuse had blown. After checking the control cabinet, my suspicions were confirmed – a circuit breaker was tripped. But this wasn’t the end, I had to find the cause of the breaker tripping. I grabbed my multimeter, found the terminal of the elements and set my meter to ‘continuity’. I tested the neutral wire to ground and just as I suspected, my meter beeped – indicating that there was a short circuit from neutral to ground. That was the easy part – the hard part now was finding where on the cable it was touching to ground. After about 30 minutes of carefully searching along the elements cable, I found the spot where the cable insulation had worn away and had touched the metal frame of the oven. A bit of new insulation done the trick, the circuit breaker was reset and the oven started up with all elements working!
On to the next job, I was required to change over a faulty fluoro light in the office. I had to wait until everyone went to lunch so I could shut the power off to the lighting circuit (people don’t like to work in the dark!), this was a quick simple change over. After completing the job, I wanted to see what was actually wrong with the light to make it fail. Using my multimeter, I tested along the various components of the light, first the wiring circuit, which tested okay, then the capacitor which seemed fine, next was the ballast – it tested faulty. I decided it was cheaper and easier to replace the whole lighting unit, rather than order and replace the ballast. That’s the thing with electronics – it usually works out cheaper to replace the whole unit, rather than replacing individual components
The biggest and most stressful job of the day was when the main conveyor line suddenly shut down for no reason – this is stressful and puts me under the pump, because for every minute this is stopped, it is costing the company hundreds, if not thousands of dollars. My first thought was to check all the individual emergency stops on the line – sometimes people can accidentally bump these, causing things to shut down. Once all those were checked and looked to be fine, I went to the main control board and could see that the line still had to power to it. I next checked all the circuit breakers, which were okay and then checked out the motor overloads – I could see one had been tripped! I pulled out the electrical drawings and found the motor overload in the drawings, and looked to see which motor was corresponding to that overload. Upon inspecting the motor, I could feel that it wasn’t turning freely, this can normally mean two things, it is either seized or that something outside the motor is jamming it. Considering the motor looked quite new, I decided to focus my fault finding on the latter. After a few minutes of inspecting, I could see that the chain on the conveyor had been jammed by a stray bolt! I wasn’t glad that the conveyor had shut down, but I am glad that it was such a easy fix! My pointy nose pliers grabbed the bolt out with ease, the overload reset and the line was back in business.
Overall the line was down for about 30 minutes, not great, but it could have been a lot worse if the motor was actually seized.
Days like today make me proud to be a maintenance electrician, it’s very rewarding once you’ve repaired a piece of machinery and got it back up and running when there’s people depending on you.