Galvanic Isolation, What does it mean for my power supply

[gavztheouch]

Hi,

After researching potential power supplies for my Granite device drivers, I discovered my DC power source needs to be Galvanicly Isolated to work with Teros drives.

What do I need to do, or check to make sure my current power supply has Galvanic Isolation?

Gav

[Al_The_Man]

It is another way of saying Electrically Isolated.
I am assuming that in this case it probably means that the P.S. should be electrically isolated from ground?
Al.

[H.O]

It means that there is no electrical connection between the primary and secondary sides of the power supply. Variacs are typical examples of transformers that (usually) doesn't have galvanic isolation between the input and output - not good in this case.

[gavztheouch]

So, is it rare to find a power supply that does not have Galvanic Isolation?

[Al_The_Man]

It is rare to find a power supply that is not isolated.
The reason is that in most parts of the world, the primary supply is common to earth ground.
With the primary and secondary isolated it allows the option of allowing the DC to float or the DC common to be connected to earth ground if it was so wished.
Your PC power supply is an example of this, it is isolated from the mains supply, but the DC common is then referenced to earth ground.
Al.

[Xerxes]

Originally Posted by H.O It means that there is no electrical connection between the primary and secondary sides of the power supply. Variacs are typical examples of transformers that (usually) doesn't have galvanic isolation between the input and output - not good in this case.

Correct.

Typical isolated power supplies are:
-Most of regulated switching power supplies
-Transformers (with isolated primary and secondary)
-Safety isolation transformers
-PC power supply is isolated but not having floating output (which is Ok, too)

Typical non-isolated (non-safe) supplies are:
-Direct rectification of mains AC voltage
-Autotransformer
-Variacs

[gavztheouch]

YouTube - CNC Power Supply 110V

YouTube - CNC Power Supply 110V

I took a video of the supply this afternoon to hopefully see if anyone might be able to identify what type of transformer I have? Its the big black lump at the start of the video. It looks like the wires come from the transformer, pass through a rectifiying diode, then into the big capacitor.

[Al_The_Man]

It is hard to say conclusively, a pause on the transformer label would have helped, but I would say there is a 99.9% chance that is an Isolation transformer.
It looks like a standard DC supply of that vintage.
The main issue of a transformer being isolated is primarily one of safety rather than functionality.
If it were a non-isolated type and the correct steps were taken to confirm the connections, it is still possible to use it, it would just be that the secondary of the transformer would be referenced to ground.
Al.

[Xerxes]

Originally Posted by Al_The_Man If it were a non-isolated type and the correct steps were taken to confirm the connections, it is still possible to use it, it would just be that the secondary of the transformer would be referenced to ground. Al.

Yes but if you insert wall plug in wrong orientation (50% chance at least with european plug) then you get mains AC voltage as ground reference which would be very dangerous.

To confirm if its isolated: disconnect all wires from it and measure ohms between primary and secondary windings. If it shows infinite ohms, it is isolating type.

Transformer info http://www.allaboutcircuits.com/vol_2/chpt_9/5.html

[Al_The_Man]

As I pointed out, it is one of safety rather than functionality.
Al.