Re: SCR based coil
"I wondered if anyone has thought about using big bipolars for the
drive. The transistors used for scan coil drive circuits in TV are rated a
at 450V and cost £0.89 each. They are therefore perfect for use in big banks
to drive a tesla."
The transistor ratings you mention above are OR values not AND values. In
other words, the transistors are able to handle either a MAXIMUM of 15A or a
MAXIMUM of 450V, but not both at the same time. This depends on the power
disapation rating of your transistor. For example if it has a 150W rating,
then you could switch 15A (max), but only at 10V, etc.
For a transistor that could switch 450V AND 15A at the same time, it would
have to be able to handle 6750 watts. That would be a VERY BIG transistor.
Plus transistors are slow devices if you compare them to a SCR, etc. A
transistor acts like a variable resistor, whereas a SCT acts more like a
switch. Using a big trigger pulse on an SCR will turn on the complete die
(semiconductor surface). This fact plus the fact that an SCR acts more like a
switch lets these devices handle very high ratings, eventhough the SCRs, etc
are not very large (size-wise).
coiler greets from germany,