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30A DRSSTC dimmer

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Danielle

Sat Aug 11 2007, 05:26AM

Registered Member #632 Joined: Mon Apr 09 2007, 01:09AM
Location:
Posts: 267

well I think i have designed a dimmer that could work up to 300A on either 120 or 240 I have all the parts but I would like it if I could have some input before starting.

also something wrong id that the UCCs are the 22 not 21s I need them because they are huge IGBTs

Electroholic

Sat Aug 11 2007, 06:17AM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

is ti just me of is the "anit" parallel diode in the wrong way

Danielle

Sat Aug 11 2007, 06:22AM

Registered Member #632 Joined: Mon Apr 09 2007, 01:09AM
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Posts: 267

umm oops its built in so thats not a problem but does it check out every other way?

Andrew L.

Sat Aug 11 2007, 09:44AM

Registered Member #515 Joined: Sun Feb 11 2007, 02:06PM
Location: Slovenia/Ljubljana
Posts: 94

Where are you going to get a bridge rectifier that can handle up to 300A?

Steve Conner

Sat Aug 11 2007, 10:50AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I know a guy who built these PWM dimmers to run stage lighting off a generator that went crazy with ordinary phase angle dimmers. It will work fine for resistive loads, but inductive loads will send it to a flaming death, because there's no path for the inductive current while the IGBT is off. I don't know what it does with capacitive loads, but I don't think it will be pleasant.

About the anti-parallel diode, you just drew it the wrong way round. Real devices have it in the other way, with the cathode to the collector.

You don't need C5.

Carbon_Rod

Sat Aug 11 2007, 11:44AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
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I don't think you will be able to drive that IGBT anywhere near 300A. If you ignore the standard switching circuit and decide to fire these with a simple driver, one can expect a safe operation curve of around 60% of the rated maximum.

For the cost, a 300A triac is simpler and cheaper (several times over) since they are often used in fuser control module replacements in copiers. If you are running outlet voltage levels with a resistive load it is an easy decision.

Bridges often have cheap and slow diodes, ( fried the 100A units often while well under the SOA.)

Gaffers tend to use correcting drive transformers at each plug box to prevent associated line and safety issues. Even short runs need GFI protection and redundant grounding systems by code.

Interesting project,

Marko

Sat Aug 11 2007, 11:54AM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Hi.

I really don't see what are you trying to achieve with this circuit. As Steve said, you will not be able to run capacitive or inductive loads. Not much use unless you need to dim like several tens of kilowatts of incandescent lights.

Normal triac dimmer wih hard firing will work well with inductive loads because of it's zero current turnoff, and capacitive loads if a small snbber inductor is added in series to limit dI/dt at turnon. Triac can be replaced with SCR's incorporated into diode bridge or doubler.

IGBT's are used for dimming as well, but that's another story. They are used simply because their turn-on speed can be slowed down and are used solely for interference reduction purposes.
They still have a zero cross detector to turn them off, and in everything else behave just like normal triac dimmers.

Steve Conner

Sat Aug 11 2007, 12:32PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Yes, I prefer SCRs for stuff like this, because they are pretty hard to destroy (all you need to protect them is a fuse) and easy to drive.

Marko and I have experimented with a load of different SCR and triac based circuits, and you can read about our efforts in other threads on the board. Here is my latest circuit, dimming a NST and neon sign :P

Marko

Sat Aug 11 2007, 01:25PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Hey, that is cool. What do all the pot's on the box do? Which circuit did you use, guessing by the size of box it's all mains-powered?

Bored Chemist

Sat Aug 11 2007, 01:36PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

If you are planning to dim a lot of lights then remember that the current through a cold lamp filament is roughly 10 times higher than the running current. With a dimmer rated for 300 amps you can probably only safely dim about a 30 amp load.

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