OK guys- I have a few PQ questions:
I am troubleshooting (3) HVAC control cabinets. Each cabinet is fed by its own 120V circuit, but all 3 share the same neutral. There is one single phase 120/24 VAC control transformer per cabinet. The transformer primary shows high levels of 3rd order harmonics, and at random times of the day, the N-G voltages are peaking at over 5 volts. They have burned up numerous boards.
X2 is grounded, and the customer asked if this is required by the NEC.?
What is an acceptable level of voltage and current harmonics? Can triplen harmonics pass through a single phase transformer, and if so, can they destroy circuit boards?
I am guessing that the harmonics from all 3 cabinets are adding on the neutral, overloading it, and causing the voltage rise on N-G. Am I on the right track?
Thanks-
Bryan
I am troubleshooting (3) HVAC control cabinets. Each cabinet is fed by its own 120V circuit, but all 3 share the same neutral. There is one single phase 120/24 VAC control transformer per cabinet. The transformer primary shows high levels of 3rd order harmonics, and at random times of the day, the N-G voltages are peaking at over 5 volts. They have burned up numerous boards.
X2 is grounded, and the customer asked if this is required by the NEC.?
What is an acceptable level of voltage and current harmonics? Can triplen harmonics pass through a single phase transformer, and if so, can they destroy circuit boards?
I am guessing that the harmonics from all 3 cabinets are adding on the neutral, overloading it, and causing the voltage rise on N-G. Am I on the right track?
Thanks-
Bryan