Electrical Shock on the Body of Dimmer Modules

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sundar-edaboard

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We have developed Dimmer module with metal body. The body is earthed with Main Earth and SMPS's Chassis Earth.

When i disconnect the 230V AC Main Earth of the module, I can measure 145V AC between the body and phase & getting electrical shock in the metal body. The dimmer is based on TRIAC. SMPS based power supply.

How to solve the problem.

Thanks in advance...


Regards,
Sundar.A
 

I suspect your selected triac is not of the isolated tab type. Check it and post diagram if possible.
Best of luck.
 
Normally Vg is 2 diode drops fom MT2. Since MT1, MT2 are 4 quadrant with polarity AC should work, except one s Hot and the other is neutral.

Neutral is grounded usually only at transformer pole thus 5% of line can be expected on Neutral from load drop.

Verify your polarity and isolation of MT2.
 

These TRIACS are insulated tabs but have internal leakage which increases to 3 mA at 125'C . Also your 220pf contributes some AC leakage therefore you will read high voltage with high impedance probe. A dummy load is needed for safety if accesible to human touch.

example of Y1 class AC rated caps in 220pF
**broken link removed**
 
Yep as long as the caps in the control circuit power supply mains filters are Class Y, it looks like at worst you need to isolate the heatsink for the triacs.

Looks like a fairly conventional DMX512 input stage lighting rack to me, I am somewat surprised that rolling your own is cost effective.

Now given this thing is going to be fed from a supply somewhat larger then domestic (32 or 63A is conventional over here),you may also wish to carefully consider the breaking capaicity of your fuses and how much you may wish to oversize your power semis by (Compare the surge current rating of the triacs with the fusing curve for your fuses).

Regards, Dan.
 
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