General > General Technical Chat
Isolation transformer - Voltage between output and ground
Ian.M:
Try reversing the primary connections and measure again. Its likely that one end of the primary is closer to the secondary, and you want that end connected to Neutral to minimise the capacitively coupled common mode voltage on the secondary.
N.B. Measure AC voltage at each end of the secondary with respect to ground and take the lower reading as the capacitive coupling is almost certainly asymmetric, as it will be between the last layer of the primary and the first layer of the secondary (or visa versa depending on which winding is on the outside)
@Siwastaja
Or build your own ESD grounding point with two 1Meg high voltage resistors, from a 1st world manufacturer, in series, properly mounted and insulated so they cant (easily) short out. Then it doesn't really matter if the ESD lead has a crappy resistor!
Zero999:
1M is low for ESD. I would go for a higher value, perhaps 10M, made with 10, 1M resistors in series. Where I used to work, one of the ESD points just went to a piece of copper foil glued to the wall, via 1M resistor, which measured about 10M to mains earth.
S. Petrukhin:
--- Quote from: EPAIII on February 11, 2024, 06:15:01 am ---But I worked with those static sensitive ICs and other components. In 45+ years how many did I destroy with static electricity discharges? ZERO!
--- End quote ---
Perhaps your skin has low resistance, or your shoes are soaked in sweat salts, etc. - there is no static charge accumulating on yours. :)
However, 45 years of practice is not a reliable refutation of science.
Nevertheless, I agree with you that the precautions for static electricity are elevated to an unreasonable drama. Like ROH, deionized water instead of alcohol, component drying is a field for business and income generation. In the West, they like to create fright and make money from it.
Most often, it is enough to remove the charge once before starting work.
jonpaul:
Stray capacitances Pri-Sec and Sec -earth will from a divicder
EMI filters add capacitances with VDE X and Y capacitors.
The currents are tiny at mains freq and usual capacitances.
Measure all the stry/parasitic, drew an equiv clt and you can see the reaspon
Jon
m k:
In my case personal ESD protection was mandatory, everywhere.
The whole area of the building was also ESD protected.
During winter times static charges were still around.
Personal wrist wrap was clearly needed.
There I also learned that major part of ESD damages are partial.
The machine is still operational, but below its standard.
Later I educated how a computer shop can stop their constant intermittent problems with installed and still warrantied memories.
Unfortunate to end user, after warrantied period the original source of the problem is moot.
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