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Basic Engineering Question - Electric Isolation

by mia077
Tags: basic, electric, engineering, isolation
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mia077
#1
Feb6-09, 12:06 PM
P: 1
I'm trying to determine exactly what electric isolation is and how to break isolation. Is Galvanic isolation the same as electric isolation? I have found some information on Galvanic but not Electrical. If anyone has a good resource to recommend on the subject I would appreciate it. Thanks
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gunslingor
#2
Feb6-09, 02:38 PM
P: 25
More information is required. What are you trying to isolate, and what are you trying to isolate from?
stewartcs
#3
Feb6-09, 02:47 PM
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Quote Quote by mia077 View Post
I'm trying to determine exactly what electric isolation is and how to break isolation. Is Galvanic isolation the same as electric isolation? I have found some information on Galvanic but not Electrical. If anyone has a good resource to recommend on the subject I would appreciate it. Thanks
I've heard the term used only in the context of electrically separating one circuit from another.

CS

MATLABdude
#4
Feb7-09, 01:07 AM
Sci Advisor
P: 1,724
Basic Engineering Question - Electric Isolation

Quote Quote by mia077 View Post
I'm trying to determine exactly what electric isolation is and how to break isolation. Is Galvanic isolation the same as electric isolation? I have found some information on Galvanic but not Electrical. If anyone has a good resource to recommend on the subject I would appreciate it. Thanks
Well, it depends on what you mean by electric isolation. The first meaning (a synonym of insulation) is just keeping your electrical thingamajig (be it a piece of electronics, a wire, or high-voltage transmission cable) from forming an electrical connection with the things / people around it. This is usually accomplished by, say, wrapping a very poor conductor (e.g. certain plastics) around your wire / cable / device, or by suspending it away from any conducting surfaces using, say, a ceramic or glass insulator.

But the other meaning, the one I suspect may be more pertinent, is to transmit a digital or analog signal from point A to point B without actually making an electrical connection and having electrons flow from point A to B. An example of this would be wireless RF transmission (though this is usually the most expensive method of isolation and thus the one that's least used).

Normally, you desire isolation (and try your best not to break it) because you can protect one side from being damaged along with the other (e.g. when you have a current surge, or an electrostatic discharge), or have different ground levels, or have especially noisy power or ground lines, and want to keep this noise isolated away from another part of the circuit.

With all the above, my usual working definition of galvanic isolation is just electric isolation:
http://en.wikipedia.org/wiki/Galvanic_isolation

To accomplish this, you'd usually use optoisolators (convert the electrical signal to light via an LED, and then convert the light back to an electrical signal via a phototransistor), or a digital isolator (converts via magnetic flux--you can think of it as sort of a very small isolation transformer).

I hope the above has been useful, or, at the very least, understandable (I tend to lose some of my understandability after a day or two without sleep).

EDIT: And reading comprehension.
Naty1
#5
Feb7-09, 08:44 AM
P: 5,632
Is Galvanic isolation the same as electric isolation?
Depends how technical you'd like to get, but yes they are basically the same. Galvanic isolation is a specific type of electrical isolation. Boats, ships and underground fuel storage tanks are typical applications requiring galvanic protection, either isolation or more commonly bonding.

In salt water marine environments,for example, galvanic isolation means that you mount and underwater piece of metal on a boat, such as a water intake (seacock) and keep it electrically isolated from everything else on the boat.

By using a rubber hose to connect the seacock to an engine and when mounted on a fiberglass hull, little if any galvanic corrosion will occur. But if that same seacock is mounted on a steel hull, it must be mounted on an insulating pad, the bolts thru the steel encased in caulking, and bolt holes in the steel are oversized to permit insulating caulk around the seacock.

Instead of galvanic isolation, the typical approach is to wire eveything together via a heavy conducting connector called bonding. Everything is in turn connected to sacrifical anodic zincs which give up electons (via ion flow)and prevent decay of the valuable seacock.

All this is a bit different than electrolysis which is often mistakenly used to mean galvanic corrosion. Electrolysis is stray current, leakage, induced corrosion while galvanic corrosion results from dissimilar metals immersed in an electrolyte (a battery).
Pumblechook
#6
Feb7-09, 11:28 AM
P: 359
There are switches called 'isolators' which are used to allow equipment or wiring to worked on in safety. They may or may are not designed to break or make current.


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