Is it a Good Thing, or a Bad Thing, that I Float my MOT's?
ScottH, Sun Apr 16 2017, 03:57AMI 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?
Re: Is it a Good Thing, or a Bad Thing, that I Float my MOT's?
Finn Hammer, Sun Apr 16 2017, 10:12AM
Scott,
What is it you are trying to protect yourself from, by standing on that rubber mat?.
Cheers, Finn Hammer
Finn Hammer, Sun Apr 16 2017, 10:12AM
ScottH wrote ...
I have to stand on a rubber mat to be safe in this scenario.
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
Re: Is it a Good Thing, or a Bad Thing, that I Float my MOT's?
ScottH, Sun Apr 16 2017, 10:21AM
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.
ScottH, Sun Apr 16 2017, 10:21AM
Finn Hammer wrote ...
Scott,
What is it you are trying to protect yourself from, by standing on that rubber mat?.
Cheers, Finn Hammer
ScottH wrote ...
I have to stand on a rubber mat to be safe in this scenario.
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.
Re: Is it a Good Thing, or a Bad Thing, that I Float my MOT's?
Dr. Slack, Sun Apr 16 2017, 04:05PM
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.
Dr. Slack, Sun Apr 16 2017, 04:05PM
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.
Re: Is it a Good Thing, or a Bad Thing, that I Float my MOT's?
ScottH, Mon Apr 17 2017, 01:22PM
That is very interesting, I never thought about the coil having a capacitance to the core. Thanks for the info.
ScottH, Mon Apr 17 2017, 01:22PM
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.
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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