0
\$\begingroup\$

I have a motor that constantly rotates in reverse, the current is measured at 5-8A, and the selenium rectifier (Fwd: 1.2A Rev: 150V) is used.But it didn't take long to burn, what should I replace it with? my circiutmy selenium rectifier

\$\endgroup\$
  • \$\begingroup\$ Why are you putting 5A through a 1A diode? This is likely a very old setup, selenium diodes were obsolete 50 years ago. Did something change recently? Was a larger motor substituted? Is the "connector" a terminal block? Is there any relay switching going on? \$\endgroup\$ – Mattman944 May 30 at 8:37
  • \$\begingroup\$ The only thing that has me hesitating to say just use a silicon diode is the word "snub" on the diagram. It could be that the reverse characteristics of the selenium diode are important in some setups, like when the terminal block is wired to use alternating current. If you are only using DC, you may not need the diode at all. But, I don't have enough confidence to say for sure, I am still struggling to understand the diagram. There are a few people here that know a lot more about motors than me, maybe one of them will have something to say. \$\endgroup\$ – Mattman944 May 30 at 8:49
  • \$\begingroup\$ you have a resistive lead, maybe add a higher resistance in series with that and use a 10A silicon diode. 6V @1.2A suggests 4 ohms might be the right ballpark, \$\endgroup\$ – Jasen May 30 at 8:58
0
\$\begingroup\$

The supply is applied between CONTROL WIRE #1 and CONTROL WIRE #3? It looks like the diode it there only to freewheel the current through the field coil (which is usually highly inductive) when power is removed. It shouldn't be taking current continuously, only momentarily on disconnection, so the continuous rating of the diode isn't the issue. The forward drop of the rectifier plus the resistance of the "RESISTIVE LEAD" would serve to decay the current quickly.

Selenium diodes are used since they have no reverse recovery issues, silicon diodes have to absorb a certain amount of charge to establish the depletion region, still allowing a short voltage spike to be generated. A Schottky diode would work in place of the selenium device if you need to replace it.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.