Triac regulator

fr0st · 18th November 2004, 06:24 AM

I'm currently working on plans for an EDM (electrical discharge machining).

Bascically is cuts metal by controlled electric discharges. The problem I have is that I need to be able to change the voltage at currents up to about 10 amps with the voltage between 50 and 200 volts.

For current limiting, I'm using a high side fet to switch in series with an inductor. A comparitor measuring the voltage drop over a load sensing resistor will control the duty cycle of the fet.

For voltage, I was thinking of using a triac to chop the AC either coming out of a transformer or directly attached to the mains. Linear regulation is impractical due to the high current and voltage. I've done simple triac switching with a microcontroller before using mains to much success in making drag lights.

What I was thinking is to use a triac to switch a portion of a mains wave to bring the voltage down to what I need. Since you can't easily switch a triac off till the AC wave goes through zero, the uC must wait a certain amount of time before turning on the triac.
By turning on the triac at the appropriate time, only a certain portion of a wave will be going through the transformer.

If conservatively fused, can I eliminate the transformer alltogether?
I'm don't really want to find a 1500w transformer.

Is this a practical way of doing it?

Any comments?

TwoSpoons · 18th November 2004, 09:11 PM

Normally you will be controlling either current or voltage but not both at the same time: for a set voltage the current is controlled by the load, for a set current the voltage is controlled by the load.

The buck converter is probably your best bet, but if you're trying to handle 1500W I'd look at using an IGBT - drives like a FET, switches like a BJT, handles big volts and big currents easily.

fr0st · 19th November 2004, 06:15 AM

This is the site I've been basing my ideas around
http://cscott.net/Projects/FabClass/final/edesign1.html

I looked into it further today and it seems it does have voltage regulation

I just didn't understand how it was being used.
Sorry about that

on with the project

18th November 2004, 06:24 AM	#1
fr0st diyAudio Member Join Date: Dec 2002 Location: Australia	Triac regulator I'm currently working on plans for an EDM (electrical discharge machining). Bascically is cuts metal by controlled electric discharges. The problem I have is that I need to be able to change the voltage at currents up to about 10 amps with the voltage between 50 and 200 volts. For current limiting, I'm using a high side fet to switch in series with an inductor. A comparitor measuring the voltage drop over a load sensing resistor will control the duty cycle of the fet. For voltage, I was thinking of using a triac to chop the AC either coming out of a transformer or directly attached to the mains. Linear regulation is impractical due to the high current and voltage. I've done simple triac switching with a microcontroller before using mains to much success in making drag lights. What I was thinking is to use a triac to switch a portion of a mains wave to bring the voltage down to what I need. Since you can't easily switch a triac off till the AC wave goes through zero, the uC must wait a certain amount of time before turning on the triac. By turning on the triac at the appropriate time, only a certain portion of a wave will be going through the transformer. If conservatively fused, can I eliminate the transformer alltogether? I'm don't really want to find a 1500w transformer. Is this a practical way of doing it? Any comments?

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Need a Triac	zedrider	Parts	1	28th September 2007 03:38 PM
SCR or TRIAC?	Wombat2	Parts	3	6th June 2006 03:21 AM
How to measure a Triac with a multimeter?	Charles Hansen	Parts	3	1st September 2005 02:25 AM
Triac Question	vinay	Pass Labs	8	26th August 2003 08:31 PM
triac's used as crowbar??	hugobross	Solid State	19	12th August 2002 04:02 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

18th November 2004, 09:11 PM	#2
TwoSpoons diyAudio Member Join Date: Oct 2004	Normally you will be controlling either current or voltage but not both at the same time: for a set voltage the current is controlled by the load, for a set current the voltage is controlled by the load. The buck converter is probably your best bet, but if you're trying to handle 1500W I'd look at using an IGBT - drives like a FET, switches like a BJT, handles big volts and big currents easily.

19th November 2004, 06:15 AM	#3
fr0st diyAudio Member Join Date: Dec 2002 Location: Australia	This is the site I've been basing my ideas around http://cscott.net/Projects/FabClass/final/edesign1.html I looked into it further today and it seems it does have voltage regulation I just didn't understand how it was being used. Sorry about that on with the project

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)