Re: [jallist] Re: Newby: How can i do this better?
- On Tue, 26 Oct 2004 08:18:04 -0000, "Vasile Surducan" <vasile@...-cj.ro>
>> You can't turn a TRIAC off. You will have to wait for a zero-So you have motor and a TRIAC in series with the mains.
>crossing before it
>> turns off itself.
> A triac is turning off when the A1-A2 current is zero or is
>changing his direction (is negative). This has nothing to do with the
>main voltage. If it has, then you can't project static relays which
>are turning off when you tell it to switch and not when the mains is
>zerror crossing. There are many tehniques to switch OFF an triac when
>you want to, no matter the mains. Even I can send you a book about
>this, will be unusefull, is in romanian. I will search on my
>database, maybe I'll found something in english.
The mains is at this moment about 100V and rising. The TRIAC is conducting a
current of , say 1A.
Do tell me how to shut the triac off in <100 us by applying voltage to the
Ir. E.E. van Andel, Fine Wire Heat Exchangers, Fiwihex B.V. www.fiwihex.com
Wierdensestraat 74, NL-7604 BK Almelo, The Netherlands eur@...
phone +31-546-491106 fax +31-546-491107 mobile +31-653-286573
> Do tell me how to shut the triac off in <100 us by applyingYou can't, but you can turn it off by applying a pulse to the triac
> voltage to the gate.
itself of the opposite polarity. IIRC this was a common way to do PWM
with thyristors, long before power mosfets became dominant in this area.
Wouter van Ooijen
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: www.voti.nl/hvu
- --- In firstname.lastname@example.org, "Wouter van Ooijen" <wouter@v...>
> > Do tell me how to shut the triac off in <100 us by applying
> > voltage to the gate.
> You can't, but you can turn it off by applying a pulse to the triac
> itself of the opposite polarity. IIRC this was a common way to do
> with thyristors, long before power mosfets became dominant in thisarea.
Eur, you'll be then surprised to found that a triac may be switched
OFF also in pure DC. The methode is highly used right now (and not
only in the past like Wouter said)for high power DC-AC variable
frequency converters. Usualy it use an auxiliary shut off thyristor
(and a phase modifying circuit). There is another world which is
dealing with this and is called "power electronics".