scr connection 1

[kingstitch]

hi Guys

If An SCR connected in series with an (AC)load,has its Anode and Cathode reversed ,will it still function.

Kingstitch

 

[Skogsgurra]

If it is connected to AC, it will have the A and C connections reversed twice per period. So that is not a problem.

If you mean that it has been mounted the "wrong way", the problem lies more in how the heat sink is grounded and how the gate/cathode wires are connected.

It seems to be a very bad idea to have just one SCR connected. Aren't there two of them? Or more?

Gunnar Englund

http://www.gke.org

 

[BrianG]

Is the SCR used for phase control of a.c. or is it producing variable d.c.?

Whilst it's normal to use a triac for a.c. control, or pairs of SCRs, it is possible to control a.c. with one SCR by connecting it across a bridge rectifier. We used to do this years ago before decent sized triacs became available.

 

[Skogsgurra]

I totally forgot about that one Brian. We did so too. But losses made us use double thyristors instead. Couldn't get rid of the heat. Had close to 200 W losses at 100 amps and bridge/SCR while double SCRs have about 40 W.

Gunnar Englund

http://www.gke.org

 

[fsmyth]

The SCR does not care which line is which, since it sees both
polarities as it functions. If you reverse the SCR, the gate
reference has changed, and the results will vary from poor to
unpredicable, depending on the circuit. Some DIAC circuits
will work anyway, but the phase angle never approaches 180
degrees.
<als>
Brian, skoggs - I am working at a plant where SCR's are
still used in induction heating inverters; 700vdc at some
ungodly amperage, SCR's used on the rectifier side and on the
inverter side. Still learning. Still amazed.
<als>

 

[Skogsgurra]

Right fsmyth,

Learning is a life-long experience. The pessimist says: "and when you know everything, you die". The optimist says: "I wonder what I will learn in my next life?"

Gunnar Englund

http://www.gke.org