Server power supplies in series.

[Pumpkinguy]

Can someone explain to me and dumb it down a little, the point of isolating the ground on one power supply when using 2 or more in series? Also, if using 3 in series for 36v do we isolate the ground on 2 of the 3 or just the middle unit if cases are touching.

If none of the cases are touching, let's say with 1/4" of plywood in between do we need to isolate grounds at all?

Thanks.

 

[fltundra]

Can someone explain to me and dumb it down a little, the point of isolating the ground on one power supply when using 2 or more in series? Also, if using 3 in series for 36v do we isolate the ground on 2 of the 3 or just the middle unit if cases are touching.

If none of the cases are touching, let's say with 1/4" of plywood in between do we need to isolate grounds at all?

Thanks.

Because the grounds would be tied together threw the ac input if you didn't isolate the low voltage ground from the metal chassis, or remove the ac ground from one.
Best to float the low voltage side of the PS to keep things safe.

 

[fltundra]

Also, if using 3 in series for 36v do we isolate the ground on 2 of the 3 or just the middle unit if cases are touching.

2 of the 3.

 

[Pumpkinguy]

2 of the 3.

Thanks. If they are taped together, jist any 2 or 2 in a specific order? Also, do I need to isolate grounds if the cases aren't touching? Thanks

 

[fltundra]

Thanks. If they are taped together, jist any 2 or 2 in a specific order?

Any two. What your looking to achieve is NO continuity between the DC ground and the AC ground(chassis) on two of the 3 PS.

http://www.tjinguytech.com/my-projects/diy-24v-47a

 

[fltundra]

Also, do I need to isolate grounds if the cases aren't touching? Thanks

yes

 

[Pumpkinguy]

yes

Thanks for everything. I read that blog the other day. I decided i am gonna do a 36v supply. I have 4 power supplies, 3 of which are brand new. I will isolate the DC ground on the first 2 in the series and leave the last one bonded.