While browsing the web for information about a problem our company is trying to solve at a customer site, I found enlightening information on your web site. Here is the problem we are troubleshooting right now. It is not be relevant whether you can provide assistance or not at this point. The main purpose of this message is to get my thoughts on paper.
Our company manufactures induction heating power supplies which we install on industrial equipment. Our power supplies are rated at 6 kwatts each and run at about 30 kHz. They run on 208 Volts 3 phase power. The AC line sees a three phase rectifier and a 30 ufd filter capacitor. No power factor correction circuits are installed within our power supplies. Total current harmonic distortion is around 30 %. Demand for each power supply is modulated from 0 to maximum power by a process control system.
A typical installation will have anywhere from 50 to 100 of our induction power supply connected to the secondary of a Wye connected main transformer. Standard electrical distribution panels with circuit breakers feed individual power supplies. Our power supplies are floating from ground as we use fully encapsulated workcoils. All power supplies are housed in a steel cabinet which is grounded to the equipment. Of course, the chassis of our power supplies are grounded to the cabinet.
We have more than two dozens induction heating system installed since 2001, totalling close to 1900 induction power supplies. All starting up successfully except one. system started up in 2003 which showed a weird problem. This system had 72 power supplies installed in one cabinet. Some power supplies started failing randomly right after the installation. Being unable to find anything wrong with our equipment or with the installation, our service engineer decided out of despair to disconnect individual ground wires running from the neutral of the transformer secondary to each power supplies. The power supplies failures stopped immediately. We scratched our heads while unsuccessfully trying to understand why running wires directly from each one of our power supplies chassis back to the main transformer neutral would cause our power supplies to fail.
Two week ago, we installed a 61 power supplies system which is behaving strangely like the one described above. We lost 8 power supplies in one day, then 10, then everything ran well for a week. Now we are loosing a couple of power supplies a day. Our service engineer is not back from the site, but he says that the power supplies are not individually wired back to the transformer neutral.
Could a large quantities of small individual power supplies, running at varying power demands, thus at varying current harmonics distortion, cause a weird phenomenon on either the voltage or the current fed from the transformer to each power supply?
Our company manufactures induction heating power supplies which we install on industrial equipment. Our power supplies are rated at 6 kwatts each and run at about 30 kHz. They run on 208 Volts 3 phase power. The AC line sees a three phase rectifier and a 30 ufd filter capacitor. No power factor correction circuits are installed within our power supplies. Total current harmonic distortion is around 30 %. Demand for each power supply is modulated from 0 to maximum power by a process control system.
A typical installation will have anywhere from 50 to 100 of our induction power supply connected to the secondary of a Wye connected main transformer. Standard electrical distribution panels with circuit breakers feed individual power supplies. Our power supplies are floating from ground as we use fully encapsulated workcoils. All power supplies are housed in a steel cabinet which is grounded to the equipment. Of course, the chassis of our power supplies are grounded to the cabinet.
We have more than two dozens induction heating system installed since 2001, totalling close to 1900 induction power supplies. All starting up successfully except one. system started up in 2003 which showed a weird problem. This system had 72 power supplies installed in one cabinet. Some power supplies started failing randomly right after the installation. Being unable to find anything wrong with our equipment or with the installation, our service engineer decided out of despair to disconnect individual ground wires running from the neutral of the transformer secondary to each power supplies. The power supplies failures stopped immediately. We scratched our heads while unsuccessfully trying to understand why running wires directly from each one of our power supplies chassis back to the main transformer neutral would cause our power supplies to fail.
Two week ago, we installed a 61 power supplies system which is behaving strangely like the one described above. We lost 8 power supplies in one day, then 10, then everything ran well for a week. Now we are loosing a couple of power supplies a day. Our service engineer is not back from the site, but he says that the power supplies are not individually wired back to the transformer neutral.
Could a large quantities of small individual power supplies, running at varying power demands, thus at varying current harmonics distortion, cause a weird phenomenon on either the voltage or the current fed from the transformer to each power supply?
