C
I have a circuit that I need help in troubleshooting. The circuit is a 3 phase 480 volt supply feeding an SCR assembly that is controlled by a 4-20ma signal from a temp controller. The output goes to a 110kva transformer where the primary is 480v and the secondary is 107v used to heat a heating configuration in delta where each heater is 36.7kw at 107volts. This is a phase fired SCR controller with RMS Current limit and an over current trip with a relay output. This includes a auto trip reset module when fault disappears. adjustment range is about 30 to 125% of units current rating limit and 30 to 200% for the over current trip. system is protected with MOV RC snubber and fuses.
The system is started and heats properly and then for an unknown reason the scrs stop firing and the unit trips on over current. I have monitored the line current and have seen nothing to cause this. The auto reset does not work and manual startup is required. I have 3 systems here so I took this unit and exchanged it with one that is working and the problem did not follow the hard ware. I am perplexed and wondering if someone has some ideas on what is going on.
Thanks
The system is started and heats properly and then for an unknown reason the scrs stop firing and the unit trips on over current. I have monitored the line current and have seen nothing to cause this. The auto reset does not work and manual startup is required. I have 3 systems here so I took this unit and exchanged it with one that is working and the problem did not follow the hard ware. I am perplexed and wondering if someone has some ideas on what is going on.
Thanks