Yesterday at work I got into an argument with an electrician over an issue with one of our machines. The machine in question has two sets of electrically heated dies. There are ninety-six vacuum dies and forty-eight cross-head dies all rated at 5700 watts each. The problem was that one row of eight cross-head dies were blowing in much greater numbers than any other machine. I said it had to be an electrical issue and Robb the plant electrical engineer said it was not based on a report from one of the electricians, and there was in fact nothing wrong. I and the rest of us in my department disagreed, after all it was our job to replace the blown dies and they came out of our budget. We eventually convinced an electrician to do a voltage test and he found out that there was a constant 500 volts on the dies. This particular machine had no voltage adjustment on the row that was giving us a problem while all the others on all the other machines did and they ran anywhere from 300 to about 420 volts depending on the heat required. I told the electrician that was the problem and that the dies were producing far more heat than they were rated at. This is where I reaffirmed my idea that you should always remember the basics.
Aubrey, the electrician, said that he couldn’t understand why there was a problem. When I said that the dies would be drawing far more current than they should and thus producing far more heat than they should he disagreed. I said it only stands to reason that the current would go up as the voltage was too high. This is where it gets good. He said “No, the current will go DOWN as the voltage goes up”. I just looked at him and then said "No, it will go UP as the voltage is increased”. He still disagreed and said that in order for the dies to produce rated power the current will go down as the voltage goes up in accordance with the laws of electricity. I just looked at him again and couldn't believe I was hearing this from a licensed industrial electrician. I then told him he was wrong and he disagreed again and asked me how I thought they would make more heat than they were supposed too. All the while this was going on the department lead-hand was present and just listening. I then said that I agree that in order to keep the power output constant the current requirement would indeed go down as the voltage was increased but the problem with that was that the power was NOT constant and in order for it be so than the resistance of the load would have to change in order to change the current. Again he disagreed. I asked him how the resistance of the die's heating element was able to be changed and he replied that it didn't. That part he got right. I finally asked him what would happen if he connected 240 volts to a 120 volt lightbulb. “It would blow” he said “BINGO!! JUST LIKE THE DIES ARE!!” I said. After a quick mental math exercise I told him that I would bet the dies were drawing between 14 and 15 amps at 500 volts based on their 440 volt rating. Again he disagree and said more like about 11.5 amps because 500 volts and 11.5 amps equals 5750 watts. I finally convinced him to go measure the current and then went off to do the job I had been doing before being side-tracked by this issue. Later the lead-hand told me that Aubrey had measured 15 amps and that he had to admit I was right. The dies were producing around 7500 watts instead of the 5700 they were rated at. No wonder they were blowing so often and at $300-400 each it was adding up fast, over $7100 last month alone for just one machine whereas we usually spend maybe $1000/month on it and sometimes nothing at all. The next step is to install a variable voltage controller for the dies at a cost of around $20,000 which will be paid for in about three months at the current rate the dies are blowing.
This just goes to prove that no matter how much you know or think you know you should NEVER forget the basics as that is what you often have to revert too in order to solve some of the most baffling of problems. From now on I must remember to ask Devon or Mike about any electrical issues that may come up.
Aubrey, the electrician, said that he couldn’t understand why there was a problem. When I said that the dies would be drawing far more current than they should and thus producing far more heat than they should he disagreed. I said it only stands to reason that the current would go up as the voltage was too high. This is where it gets good. He said “No, the current will go DOWN as the voltage goes up”. I just looked at him and then said "No, it will go UP as the voltage is increased”. He still disagreed and said that in order for the dies to produce rated power the current will go down as the voltage goes up in accordance with the laws of electricity. I just looked at him again and couldn't believe I was hearing this from a licensed industrial electrician. I then told him he was wrong and he disagreed again and asked me how I thought they would make more heat than they were supposed too. All the while this was going on the department lead-hand was present and just listening. I then said that I agree that in order to keep the power output constant the current requirement would indeed go down as the voltage was increased but the problem with that was that the power was NOT constant and in order for it be so than the resistance of the load would have to change in order to change the current. Again he disagreed. I asked him how the resistance of the die's heating element was able to be changed and he replied that it didn't. That part he got right. I finally asked him what would happen if he connected 240 volts to a 120 volt lightbulb. “It would blow” he said “BINGO!! JUST LIKE THE DIES ARE!!” I said. After a quick mental math exercise I told him that I would bet the dies were drawing between 14 and 15 amps at 500 volts based on their 440 volt rating. Again he disagree and said more like about 11.5 amps because 500 volts and 11.5 amps equals 5750 watts. I finally convinced him to go measure the current and then went off to do the job I had been doing before being side-tracked by this issue. Later the lead-hand told me that Aubrey had measured 15 amps and that he had to admit I was right. The dies were producing around 7500 watts instead of the 5700 they were rated at. No wonder they were blowing so often and at $300-400 each it was adding up fast, over $7100 last month alone for just one machine whereas we usually spend maybe $1000/month on it and sometimes nothing at all. The next step is to install a variable voltage controller for the dies at a cost of around $20,000 which will be paid for in about three months at the current rate the dies are blowing.
This just goes to prove that no matter how much you know or think you know you should NEVER forget the basics as that is what you often have to revert too in order to solve some of the most baffling of problems. From now on I must remember to ask Devon or Mike about any electrical issues that may come up.
