tha attached PDF is a schematic of what i have so far Please tell me if there is anything wrong

Styx;

The oscilator in your diagram, is the 0 and I0 0v and +5v respectivly or -5v and +5v also what frequency does this need to run at?

Does G1 need to be a + or - trigger?

Attached Files

Wave.pdf (17.7 KB, 16 views)

 

I'm sorry, I know this isn't helpful but it just looks worng, unfortutnately I don't have time at the moment to tell you what's wrong with it at the moment as I need to go now.

__________________
I also post at the following sites:
http://www.stop-microsoft.org http://www.heated-debates.com
Screen name: Aloone_Jonez
And http://www.silicontronics.com, same screen name as here.

 

1) As stated the "gate-drive" I sketch won't really work - it was ment as a concept (it should have a couple of IC's really), ie how to get a floating voltage to teh gate (as it stands it suffers from slow turn-off. As I said I don't really like transformer-based gate-drives (hence why no real detail in that quick sketch).
I much prefer just dropping down say a: HCPL-3140-000E (opto gate-drive) with a IE0515D (5V in, 15V out isolated DCC converter). Add a couple of cap's across the output of the DCC (6uF and a 100nF), add a 200R gate resistor with gate terminating resistor and you have a very capable gate-drive

2) Again with the gate-drive, you have a local-cap of 100uF, it definitly won't work with that! - if you were going for the XFMR isolated gate-drive, said cap needs to be small to enable fast switching times (few nF). A fully-ON FET won't draw hardly any current through its gate and that cap is more just to smooth out what the rectifier pushes out

3) yr main AC rectifier really should have a transformer on it to provide isolate for safety

4) there is no DC-link capacitor for this converter, as it stands yr DC-link will follow a fully-recitifed profile. IE humps. Put a big capacitor down (NOTE ripple-current rating depending on how much current you will be sinking into load)

5) the FET's need reverse diodes otherwise the whole thing will blow up with an inductive load

__________________
Nothing is impossible.
Once a problem is realised, the rest is just details

 

Thanks for the diagnosis heres a new schematic

Attached Files

Wave2.pdf (17.3 KB, 16 views)

 

So will this one work or have i missed something?

 

That still looks wrong to me.

What's the purpose of the potential dividers and capacitors on the MOSFETs' gates?

What's T2? Is it an isolation transformer? If so good idea, well done!

There's no filter capacitor on the 240V rectifier.

__________________
I also post at the following sites:
http://www.stop-microsoft.org http://www.heated-debates.com
Screen name: Aloone_Jonez
And http://www.silicontronics.com, same screen name as here.

 

Its lacking some finite details but concept-wise it is virtually there

At a guess it would be a series gate-resistor to control the charging of the FET and a terminating resistor to pull the gate down to its source
a 1k & 1k values however are wrong.
A 200R for the series resistor and maybe a 10k from gate-source maybe

Yes, but he is gonna have to check the VA rating and all that jaz\

THAT is definitly needed, no questions asked at all

__________________
Nothing is impossible.
Once a problem is realised, the rest is just details

 

The opto-coupler gate drives and DC-DC converters are incorrectly connected to the MOSFETs.

It looks like he's connected the output from the DC-DC converter to the gates via potential dividers with capacitors from the gates to sources.

He wants to connec Vcc and Vee on the gate drive opto-isolator IC to the + and 0V of the DC-DC converters, the gate drive outputs to the gates (a 10hm: resistor or ferrite bead might be required here) and the LEDs to the PIC's outputs.

__________________
I also post at the following sites:
http://www.stop-microsoft.org http://www.heated-debates.com
Screen name: Aloone_Jonez
And http://www.silicontronics.com, same screen name as here.

 

Ive got to admit that most of this is confusing me I have done a bit of electronic before but usually same simple timer and switching circuits and nothing with mains.

The values on the schematics are just the standard one that are in the programming im not sure what values they should be.

these are the dc-dc converters that i was going to use http://www.rapidonline.com/netalogue/specs/84-2510e.pdf I took the pin configurations from them.

 

This bit i dont understand

 

Have you looked at the datasheet for the opto-isolator IGBT/MOSFET date driver IC you're using?

The output goes the the MOSFET's gate, to avoid high frequency oscillation there should be a low value resistor between it and the gate.

If Styx doesn't return in a couple of days I'll post a schematic demonstaring how to drive one MOSFET using the DC-DC converter and the optoisolated gate driver IC.

__________________
I also post at the following sites:
http://www.stop-microsoft.org http://www.heated-debates.com
Screen name: Aloone_Jonez
And http://www.silicontronics.com, same screen name as here.

 

try this

--padding--

Attached Images

driver.png (17.0 KB, 11 views)

__________________
Nothing is impossible.
Once a problem is realised, the rest is just details

 

Thanks alot guys youv'e been a real help

Hopefully ive got this right this time, I think ive understood what youve been saying

just a couple of questions, can 2 FET's be driven from 1 driver to save on components and board space? and I want to protect the pumps from any possible damage and was thinking of puttting a fuse in, would i put this after the board on the 240VAC out?

Attached Files

Wave3.pdf (21.3 KB, 5 views)

 

Also I cant find the MCPL-3140-000E in the UK suppliers that i use would this one be a suitable replacement? http://docs-europe.electrocomponents...6b80028805.pdf

 

That ought to do the job, although it isn't as good to the IC origionally suggested, it's more than good enough for this application.

__________________
I also post at the following sites:
http://www.stop-microsoft.org http://www.heated-debates.com
Screen name: Aloone_Jonez
And http://www.silicontronics.com, same screen name as here.