Hep please - what resistor size.

[punkieys17]

I am flummoxed. This is a commercial circuit from a pump. It incinerated the resistor and the thyrstor. The thyrsitor is correct but when i connect the pump and energise the reed switch it works once or twice then the thyristor burns out.
The only variable is the resistor size. Its on a 240V AC line. Yhe Igt is stated between 5 & 50MA and the Vgt at 1.2v. Please someone advise to the correct size...and show me the calculation. Any help greatly appreciated. The circuit diagram is complete as in the unit.

 

[Bluejets]

200R...??

 

[kellys_eye]

but when i connect the pump and energise the reed switch it works once or twice then the thyristor burns out.

Is the motor ok? Sounds like it's stalled, seized or otherwise knackered to me.....

 

[bertus]

Hello,

Have a look at the attached application note.

Bertus

 

[kellys_eye]

Might also be because you have the device connected wrongly - double check the pinout and your orientation.

 

[Sunnysky]

i would use a ZCS opto-triac instead of a Reed switch.

 

[danadak]

SCR / Triac Handbook :

https://archive.org/download/scrmanual/SCR%20MANUAL.pdf

Regards, Dana.