# I was trying to build an LTspice model for three phase uncontrolled rectifier.

#### aiemon

Joined Oct 28, 2017
3
The problem that i am facing at the time of simulation is with grounding. The ground of three phase source should be separated from the bridge. I was trying to use transformer to separate the ground but it is giving faulty wave shape. My point is how to insulate the rectifier bridge from the ground of source. Help in this issue will be much appreciated.

#### crutschow

Joined Mar 14, 2008
25,242
I don't quite understand your problem.

Ltspice requires only one ground point and you can put that wherever you want.

#### aiemon

Joined Oct 28, 2017
3
I don't quite understand your problem.

Ltspice requires only one ground point and you can put that wherever you want.
The simulation circuit that I have posted, the value of voltage and current is not the same as it shows in the calculation. Again main purpose of my query is to find a way to isolate the three phase supply from the bridge. This isolation problem is the main challenge to make it functional by far that i have found.

#### ajune

Joined Oct 24, 2017
10
Hi,

Please elaborate further the word isolate the 3 phase supply from the bridge.
Its normal already providing ac input to the bridge as per your schematic.

#### crutschow

Joined Mar 14, 2008
25,242
The simulation circuit that I have posted, the value of voltage and current is not the same as it shows in the calculation.
How are they different?
What calculation?
Again main purpose of my query is to find a way to isolate the three phase supply from the bridge. This isolation problem is the main challenge to make it functional by far that i have found.
I see no reason for having this isolation.
I believe you are chasing a non-existent problem unless you can better explain why it is needed.

#### Alec_t

Joined Sep 17, 2013
11,501
You can 'isolate' the bridge from ground by putting a 100Meg resistor between the two. That will keep Spice happy.

#### aiemon

Joined Oct 28, 2017
3
You can 'isolate' the bridge from ground by putting a 100Meg resistor between the two. That will keep Spice happy.
Where should I put this resistor? Can you please specify? In the common ground of all sources or in between the ground and bridge?

#### crutschow

Joined Mar 14, 2008
25,242
Here's an LTspice simulation of a 3-phase rectifier circuit, which works fine with one ground at the bridge output.

#### Alec_t

Joined Sep 17, 2013
11,501