Re: Diodes and SCR's

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>

> got a question about diodes and scr's:
> can an scr be used as a diode?

	Yes.  In a couple of ways.

> well....  can 4 scrs be used as a full wave bridge rectifier???

	Yes.  Or two can be used, with two regular rectifiers.
	(Usually r are not used for straight rectification, as
	diodes are less expensive than SCRs of equivalent rating.)

> and if they can be used as a FWBR  how does 
> one wire up the gates to do so??    

	Roughly/simplistically:
	Strap the gate to the Anode, usually with a resistor.
	SCR should turn itself on.  Can get more
	sophisticated.

	(One can do a 'controlled rectifer' with phase control to
	drive the gates, to control the voltage, analagous,
	tho less robust, than a variac.  Usually uses only
	two devices to control, the others being static
	rectifiers.  The 'two SCR' version is a lot simpler,
	as gate drive gets tricky)

 
> I just found out that the diodes I have been using in my power supply 
> are rated for 100 V 70 A ( et up as a full wave BR)

	Is this the device rating, or the bridge rating?
	(eg 1 amp diodes in a bridge make up a bridge capable
	of 2A....)

> and Ive been pumping 300VAC into them at 60A ....  either I blew

> up something and  didnt see it go

	UNlikely at those power levels, I'd expect.
	See, hear, smell would all notice.  8)>>

> OR...  these diodes are EXTREMELY underrated and are handling

> the abuse.

	There is margin in all ratings, varying from device to
	device and from type to type.  Also, the two diodes in
	either polarity  are in series, so (with luck) the
	overvoltage will share...  (usual concerns about
	devices in series not sharing equally apply...)
	best
	dwp

...the net of a million lies...
	Vernor Vinge
There are Many Web Sites which Say Many Things.
	-me