jcole
Senior Member
- Location
- Lawrenceburg, Kentucky
Good day Guys and Gals.
I have a Russell Electric transfer switch that switches to generator with loss of utility. It feeds an MCC that has 6 motors and vfds. 480Y system. The switch is sized for 800amps and under full load the MCC will draw about 725 amps. We hardly ever run at full load. Usually around 300 amps on a typical day.
The contacts for one of the phases on the Russell Electric switch burned up after about 2 years and created a single phase condition. The first time it happened I thought it was because the original electrical contractor had milled out the lugs with a dremel tool or something. They did this because the lug wasn't big enough for the oversized conductors that were specified by our engineer consultant. I thought this was the culprit of the heat.
We replaced the hole ATS with the correct size lugs. We started doing thermal imaging test every 90 days after the new was installed. We have not seen any thing unusual on the images. It has been 2-3 years since it was installed. Today, the exact same thing happened again. One of the phase contacts overheated and created a phase loss. The area that is overheating is hard to detect with the camera because they are hidden behind other parts of the switch. I am assuming it has been slowly failing over time and we could not get a good image of it. The conductor terminations were torqued to manufacture instructions.
Any of you ever had an issue like this with a Russell Electric ATS? I was wondering if harmonics could create heat on a phase conductor like this? My little experience with harmonics is that they usually affect the neutral or transformer not a phase conductor.
I would appreciate any input you might have.
Thanks for any replies.
I have a Russell Electric transfer switch that switches to generator with loss of utility. It feeds an MCC that has 6 motors and vfds. 480Y system. The switch is sized for 800amps and under full load the MCC will draw about 725 amps. We hardly ever run at full load. Usually around 300 amps on a typical day.
The contacts for one of the phases on the Russell Electric switch burned up after about 2 years and created a single phase condition. The first time it happened I thought it was because the original electrical contractor had milled out the lugs with a dremel tool or something. They did this because the lug wasn't big enough for the oversized conductors that were specified by our engineer consultant. I thought this was the culprit of the heat.
We replaced the hole ATS with the correct size lugs. We started doing thermal imaging test every 90 days after the new was installed. We have not seen any thing unusual on the images. It has been 2-3 years since it was installed. Today, the exact same thing happened again. One of the phase contacts overheated and created a phase loss. The area that is overheating is hard to detect with the camera because they are hidden behind other parts of the switch. I am assuming it has been slowly failing over time and we could not get a good image of it. The conductor terminations were torqued to manufacture instructions.
Any of you ever had an issue like this with a Russell Electric ATS? I was wondering if harmonics could create heat on a phase conductor like this? My little experience with harmonics is that they usually affect the neutral or transformer not a phase conductor.
I would appreciate any input you might have.
Thanks for any replies.