1. Home
  2. Electronics Design
  3. Total controlled SCR tripase bridge problem

Total controlled SCR tripase bridge problem

Hi,

i've a system that a total controlled thipase bridge wich control the primary of an step-up transformer. The secondary has a traditional greatz bridge. With a pasing control of the scr i can regulate the dc output from

300-t0 4000 Vcc.

Some day ago this "machine" had this problem:

withauot load i set a DC output ant the the set point is maintened but there is an oscillation with a very low freq. around 600mHz.

When i connect the load the dc tension start to oscillate and the scr bridge give strange noise.

After these oscillation sometimes the dc stabilize and bridge "sound" good.

So.........is it possible that a scr foult?

How can i check if a scr is dead?

Thanks for any help

Reply to
max
Loading thread data ...

It is extrewmely unlikely that there is a bad SCR. You can check the output for a characteristic notch in the DC voltage at 1 x like frequency. It will be much worse under load.

But, a .6 Hz fluctuation has to be a control loop problem. Was this control designed to regulate with no load? It is quite possible an electrolytic capacitor in the loop compensation circuit has deteriorated.

A shorted SCR would cause a fuse to blow in spectacular fashion. An open SCR is unlikely. A failure of a component in the SCR gate driver could cause one SCR to never be fired, but it seems unlikely this is actually the problem you are seeing.

Jon

Reply to
Jon Elson

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.