Trying to get the signal generator for IGBT gate driver to be isolated from the rest of the circuit. The circled ground symbols and chassis ground aren't connected which is why its labeled as floating.

Is using a transformer in the circuit going to isolate it or there is a better method for this?

 

hi p48,
Why does that section have to be floating.?
E

 

Although you have an opto-isolator in the signal path, the supply is common to both parts. So no, not isolated.

For a true isolated IGBT gate driver you could use an optio-isolator in the signal path and use an isolated supply to power the gate drive circuit - possibly using a DC-DC converter.

Edit:
You can get special ICs that do the isolation and gate drive all in one such as this and this but you will still need an isolated power supply for each IC.

 

OK. I see. The circuit between the transformer and opto-isolator is floating. My mistake!

Would be good to ground all the points shown in your circuit for safety.

 

I was making sure the signal source is infact its isolated from the rest of the supply circuit.

And this is very good. But no isolation is perfect so if the signal source is not grounded the whole signal-source circuit could float at some unknown and possibly dangerous voltage. Better for safety and ease of maintenance and fault-finding to have the circuit grounded.

 

hi,
The leftside twin connector has the 'float' gnd, so how does the remainder of the circuit get a common path.?
E

 

If the circuit is actually connected exactly as drawn, then the section is indeed isolated, except for whatever leakage exists in the transformer. So is the complaint that it is not isolated? The use of that symbol often leads to errors and so if a circuit is to be constructed as an isolated section it is much wiser to draw that connection as another line in the circuit drawing. Certainly it takes a bit more effort to draw, but it avoids construction errors that can be rather expensive.
And the circuit as shown certainly does have an isolated DC to DC converter. BUT the very top line and the ground symbol of the elements past the opto-isolator leave that section not isolated.

REDRAW the circuit with all of the grounds shown as conductors and the cause of the lack of isolation will be immediately obvious.

So the question stands, what do you want to isolate from what?

 

The original circuit could have the desired isolation fairly simply. First, move the very top line connection that supplies the circuit to the right of the opto-isolator to instead connect to the + side of that first 220 MFD capacitor just past the rectifiers. Then change the ground connections from all of the devices to the right of the opto isolator to the same common as the diode bridge negative terminal. At that point the whole output section will be isolated from the incoming connection. It may be that the isolated power transformer will ned to deliver more power, but that change should not affect the isolation.