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Re: SCR based coil



Hello Nick, 
 
You wrote:
"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
15A
 at 450V and cost 0.89 each.  They are therefore perfect for use in big banks
 to drive a tesla."
SNIP

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,
Reinhard