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Registered Member #18429
Joined: Sat May 18 2013, 02:05AM
Location:
Posts: 19
I am building a general-purpose inverter (60Hz AC --> 40-140 kHz AC) for powering flyback transformers, induction heaters, etc. The project link I'm referencing can be found here: http://uzzors2k.4hv.org/index.php?page=multiinverter I am aware of the hazards present from the high voltages in themselves; however, what I am more concerned about is the fact that schematic shows the a direct connection to unisolated mains.
If it is possible to do so safely, I would like to use this circuit without an isolation transformer. However, that brings up several question:
1. The author built his inverter within a salvaged ATX power supply metal enclosure. Can I ground the metal case, or would this cause problems due to the fact that the circuitry runs unisolated?
2. If I did ground the metal case, I would certainly need to ensure that the MOSFET heatsinks did not make contact with the case---correct? Is there a practical way to isolate the heatsinks from the case?
3. I realize it would be exceedingly dangerous to leave the case ungrounded, with the unioslated circuit. If this were necessary (due to 1 and 2), I suppose enclosing the ATX case with plastic would provide enough safety?
Also keep in mind that I would be the only person using this inverter--it will not be sold/installed/used in an environment with anyone else, just to clear up potential liability concerns.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Grounding the case shouldn't be a problem. I would also connect the ground rail of the control circuit to the case ground.
You can isolate the heatsinks from the case. This is usually done by mounting them on a circuit board and mounting the board to the case. But nylon screws and nuts are also handy. Alternatively, you can connect the heatsinks to the case and isolate the MOSFETs from the heatsinks using thermal insulating washers.
Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
I ran my inverter off of an isolation transformer connected to the mains. I think having a direct mains connection is asking for a problem. Why take the chance when an isolation transformer gives you another layer of protection?
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Mains-powered project considerations
