My electrician was in the shop today to wire up a CNC machine for us and while i had his ear i asked him if there was a reason we do not seem to have a neutral line coming from the utility lines outside. He told me that our 480Tx makes its own neutral and that we do not need the neutral from the utility. Makes sense to me i guess but then what do i know. But i have had a hunch for some time that the lack of a neutral is what has been causing our machine problems. Let me explain our power setup and the problems we have had for a long while now.
1. The 3 phase utility service is connected to a 480Y transformer which creates its own neutral and does not have a neutral coming from the utility. The 3 phase plus neutral coming from this 480Tx goes into a large main breaker where it then branches out into two feeds. One feed has the 3 phase plus neutral fed into an over head bus bar running through the shop. This feeds 480v 3 phase power to some of our cnc equipment.
2. The second feed from the 480y has 3 phase with no neutral going into a 208Y tx which creates its own neutral. Coming out of the 208tx is 3 phase 208y with a neutral. The 3 phase is fed into a main breaker. From the main 208 breaker the 3 phase then goes into a junction box which has a seperate bar for each of the three phase legs. All power to each individual breaker box down line whether it be single phase, dual phase or three phase is connected to the 3 phase bars in this junction box. The neutral wire from the 208tx runs into the junction box and is connected to the buildings ground rod and also all other ground wires going to machines and each breaker box down line. Our single phase is derived from the 208.
How our cnc equipment is wired up -
Most all of our machines are powered from the 208V. They have three phases coming from a breaker and also a ground wire connected to the building ground bar, the power wires then go into a disconnect switch on the back of the machines and the ground wires connect to a ground terminal inside the machine cabinet. All machines then pass the three phase into a built in transformer and after which it branches out inside the machine to numerous electronics boards and motor drivers. When powering machines off we turn the controls off and then switch off the disconnect on the back of the machine so all CNC machines are physically disconnected from the grid when not being ran.
Here is our nightmare problem that has eluded us thus far almost exclusively on our 208V equipment. Every couple weeks or so we will have a CNC machine or two blow out a control board when the machine is switched on in the morning. I have a tech man who is capable of fixing our electronics boards and i have enough problems to keep him busy 40hrs a week every week. This ONLY happens in the mornings when a machine is switched on and powered up. It is rare for our machines to blow a board or fault out during operation, if the machine powers up in the morning they run all day no problem. Just yesterday we had 4 out out of 5 machines trip the machines main power breaker built into the machines when they were switched on in the morning. We simply switch the power off, flip the breaker up and power them back on and they work fine. This happens quite often, and when it does its usually not just one machine that does it its multiple machines all in the same morning. When this happens we check voltages line to line and line to neutral and have never found anything out of whack. I have used recording meters on the main lines and even on machines themselves before and could not find anything wrong. I have had an electric consultant company come in and meter our power briefly. They didnt find anything and their recommendation was to rewire the plant. I cant afford to spend $50k rewiring the whole plant to try and fix the problem if i dont know its going to fix our problem. We are a small business and with the economy the way it is its all we can do right now to keep our honest hard working employees employed. I would certainly spend the money fixing the problem if anyone knew what would fix it. But throwing a ton of money at something just hoping it fixes it isnt an option right now unfortunately. I am seeking sound advice from people who certainly know more about this sort of thing than i do and am hoping someone maybe has seen this type of problem before.
1. The 3 phase utility service is connected to a 480Y transformer which creates its own neutral and does not have a neutral coming from the utility. The 3 phase plus neutral coming from this 480Tx goes into a large main breaker where it then branches out into two feeds. One feed has the 3 phase plus neutral fed into an over head bus bar running through the shop. This feeds 480v 3 phase power to some of our cnc equipment.
2. The second feed from the 480y has 3 phase with no neutral going into a 208Y tx which creates its own neutral. Coming out of the 208tx is 3 phase 208y with a neutral. The 3 phase is fed into a main breaker. From the main 208 breaker the 3 phase then goes into a junction box which has a seperate bar for each of the three phase legs. All power to each individual breaker box down line whether it be single phase, dual phase or three phase is connected to the 3 phase bars in this junction box. The neutral wire from the 208tx runs into the junction box and is connected to the buildings ground rod and also all other ground wires going to machines and each breaker box down line. Our single phase is derived from the 208.
How our cnc equipment is wired up -
Most all of our machines are powered from the 208V. They have three phases coming from a breaker and also a ground wire connected to the building ground bar, the power wires then go into a disconnect switch on the back of the machines and the ground wires connect to a ground terminal inside the machine cabinet. All machines then pass the three phase into a built in transformer and after which it branches out inside the machine to numerous electronics boards and motor drivers. When powering machines off we turn the controls off and then switch off the disconnect on the back of the machine so all CNC machines are physically disconnected from the grid when not being ran.
Here is our nightmare problem that has eluded us thus far almost exclusively on our 208V equipment. Every couple weeks or so we will have a CNC machine or two blow out a control board when the machine is switched on in the morning. I have a tech man who is capable of fixing our electronics boards and i have enough problems to keep him busy 40hrs a week every week. This ONLY happens in the mornings when a machine is switched on and powered up. It is rare for our machines to blow a board or fault out during operation, if the machine powers up in the morning they run all day no problem. Just yesterday we had 4 out out of 5 machines trip the machines main power breaker built into the machines when they were switched on in the morning. We simply switch the power off, flip the breaker up and power them back on and they work fine. This happens quite often, and when it does its usually not just one machine that does it its multiple machines all in the same morning. When this happens we check voltages line to line and line to neutral and have never found anything out of whack. I have used recording meters on the main lines and even on machines themselves before and could not find anything wrong. I have had an electric consultant company come in and meter our power briefly. They didnt find anything and their recommendation was to rewire the plant. I cant afford to spend $50k rewiring the whole plant to try and fix the problem if i dont know its going to fix our problem. We are a small business and with the economy the way it is its all we can do right now to keep our honest hard working employees employed. I would certainly spend the money fixing the problem if anyone knew what would fix it. But throwing a ton of money at something just hoping it fixes it isnt an option right now unfortunately. I am seeking sound advice from people who certainly know more about this sort of thing than i do and am hoping someone maybe has seen this type of problem before.