DIYbanter - View Single Post - C4 Racing from Newbury

Andrew Gabriel

In article ,
(greenaum) writes:
On Tue, 15 Feb 2011 18:06:00 -0000, "Mortimer"
sprachen:

I was very proud to be a member of the winning team who managed not to blow
their thyristor up

Was that one of the initial criteria?

I ask because it seems pretty stupid using such a marginally specced
component. Surely variable mark/space includes 100:0. Even 95:5 must
have been pushing it for the component.

Also... don't thyristors stay switched on as long as they have enough
voltage across them?

No.

Or was it AC flowing through them?

Well, DC flowing through them (they only pass current in one direction).

There are also gate turn-off thyristors (GTO) which can also be turned
off using the gate electrode, but the last time I used a thyristor was
before GTO thyristors were invented, so I've never played with one.

I'm sure
you'll have known this at the time, but wouldn't a simple transistor /
FET have been better?

They're much easier to blow up. A thyristor can only be On or Off, and
in neither state is there scope for enormous power dissipation
(although the GTO thyristors do have some more explosive failure modes).
On the other hand, a FET is continuously variable beween On and Off,
and in the half-On state, a tiny package measuring just a few mm²
can generate 1000's of times the power dissipation you might have been
designing for if intended for On/Off switching. FETs are also static
sensitive.

--
Andrew Gabriel
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