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Registered Member #61373
Joined: Sat Dec 17 2016, 01:45PM
Location: San Antonio, TX
Posts: 87
I have the cores of 2 MOT's connected electrically, and they work just as good without the cores being Earth grounded. The secondaries won't arc any current to the Earth when floating, just a small weak spark (maybe a few ma judging by the spark). I can generate the same large arcs from the HV hot to the core potential as I can when the MOT's are grounded.
When I have the cores grounded, I still get the same power output, but the current will flow to Earth. I have to stand on a rubber mat to be safe in this scenario.
Is it a good thing that I run the MOT's this way? Why is there a weak spark to Earth in the floating setup?
Registered Member #61373
Joined: Sat Dec 17 2016, 01:45PM
Location: San Antonio, TX
Posts: 87
Finn Hammer wrote ...
ScottH wrote ...
I have to stand on a rubber mat to be safe in this scenario.
Scott,
What is it you are trying to protect yourself from, by standing on that rubber mat?.
Cheers, Finn Hammer
Current potentially going through my "chicken stick", to me, then to ground. You never know what HV may do sometimes. Its to isolate me from the ground.
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
The mains winding is fully insulated from the core, with probably a few 10s pf pF capacitance between mains winding and core. As a MOT is rated to be connected to mains, we already know that this insulation has survived tests at 1500V ac, and maybe more.
If the core is not grounded, there is still a path from core to 'groundy' wires like live and neutral, via this capacitance. 2.1kV across a few 10s of pF, even at the low frequency of a few 10s of Hz, is still likely to give a visible, if weedy, discharge to ground.
Registered Member #61373
Joined: Sat Dec 17 2016, 01:45PM
Location: San Antonio, TX
Posts: 87
Dr. Slack wrote ...
The mains winding is fully insulated from the core, with probably a few 10s pf pF capacitance between mains winding and core. As a MOT is rated to be connected to mains, we already know that this insulation has survived tests at 1500V ac, and maybe more.
If the core is not grounded, there is still a path from core to 'groundy' wires like live and neutral, via this capacitance. 2.1kV across a few 10s of pF, even at the low frequency of a few 10s of Hz, is still likely to give a visible, if weedy, discharge to ground.
That is very interesting, I never thought about the coil having a capacitance to the core. Thanks for the info.
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Is it a Good Thing, or a Bad Thing, that I Float my MOT's?
