How are my grounds

147

01:27:57

Two different potential voltages need to be common grounded so there is no floating ground to create a static charge and burn out you're electronic components with spurious spike's. Two different voltages like 177v & 16.7volt, are grounded in this drawing & you will always see this connection in a air conditioning system where motor components are used & needed. 

The motors produced a large back EMF which in turn is a static charge on the field windings,  this charge passed back to ground normally but can damage electronic components if  grounding is improper or the field windings start to fail.

All components hooked to mains must be grounded by electrical code. So there is never a chance of floating ground potential.

published 10 years ago

thebugger

10 years ago

It's all good. No floating grounds. That's the perk of having a transformer it allows you to physically (galvanically) separate one part of the circuit from the other. This came in handy with old tv's where the mains would usually get rectified, meaning that the chassis can often become dangerously charged at mains potential and if you had to plug in earphones, they'd be at mains potential too. Imagine having them on your head. Brain dead instantly. So decoupling transformers used to be used to make a separate ground, that doesn't depend on the live or neutral of the plug 🔌

yra

10 years ago

Ouch!! No kidding brain dead. I was not aware of this. Thanks for the info. Mostly i have worked with commercial equipment in kitchens and factory type stuff from the past 30+ years, not to much call for tubes.

yra

10 years ago

I did have a ham amp bite me one time, you can bet i installed a bleed resistor right than, well maybe when my eye's stopped spinning.

thebugger

10 years ago

I recently got a few HV caps diacharged through me, and worst through my two hands, so the first thing i put was a bleeding resistor too. Anyway up to the 1990s mains rectification was a widely uses technique to skip on the costly and bulky power transformers. That led to a very high electrocution risk, and this technique was abandoned. Even transistorised TV's used this technique for the cathode ray tube, which also required high voltages. Anyway, transformers are a good way to galvanically separate the live and neutral, so that you may choose a permanent position for your ground.

yra

10 years ago

Galvanic is the right word, being all you taste after is metal. Galvanically is a word i have not heard or used in a decade and I think the last time was for plumbing pipe. That is my new old word for the day.

rich11292000

10 years ago

I was installing new ballasts in a truck shop that put out 750vrms/1060vpeak/2121vpeaktopeak. The high frequency output would cause voltage to escape the insulated wires. Touching the metal light while shoving the hot wires in, it felt more like a burn than a shock, burnt my arm hairs and shaved me like a razor.

thebugger

10 years ago

Yes after 1000V the current is high enough to burn the skin, rather than cause the muscles to spasm. That is good in a way, because the energy us high enough to knock you off the source, and not making you get a tighter grip.

yra

10 years ago

I never liked working on more than 600 volts so very dangerous have to keep track of all fingers, too easy to touch things in a control panel.

thebugger

10 years ago

Keep it as a rule of thumb, if you're working with voltages higher than 60V, keep one hand behind the back at all times. I've had a few shocks between the two hands, and it's very dangerous.

add comment in editor