sup, Electronics newbie here trying to design my first regulated

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Anonymous
2016-02-19 20:48:37 Post No. 949132
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Anonymous 2016-02-19 20:48:37 Post No. 949132 [Report]

sup, Electronics newbie here trying to design my first regulated DC power supply. Why does my transformer explode when I simulate my circuit in multisim?
I have managed to prevent damage to the transformer by placing a high power resistor at 25 Ohms between the output of the bridge rectifier and the capacitor bank, however this causes a large performance decrease. Is there a way to fix this without significantly reducing my output?
The transformer should output approx. 24Vrms AC.

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Anonymous 2016-02-19 21:12:02 Post No.949139
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Anonymous 2016-02-19 21:12:02 Post No.949139 [Report]

I had a similar problem with some other simulation software (livewire). Had a similar setup: transformer -> bridge -> caps -> regul -> caps -> load. For some reason, the bridge diodes keep exploding at the start of the simulation. Never solved the issue with the simulation, but our best guess at that time was that the unloaded caps (at the start of the simulation) were threated as a short circuit, making the diodes blow.

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Anonymous 2016-02-19 21:35:05 Post No.949143
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Anonymous 2016-02-19 21:35:05 Post No.949143 [Report]

>>949132
Uh... Because the peak value will be around 34V and you have a 25V zener there?

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Anonymous 2016-02-19 21:39:19 Post No.949144
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Anonymous 2016-02-19 21:39:19 Post No.949144 [Report]

>>949143
I decreased the transformer output voltage to 12Vrms and removes the zener, the same thing happens. I tried putting a voltage divider in place of the zener aswell to no effect

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Anonymous 2016-02-19 21:42:06 Post No.949145
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Anonymous 2016-02-19 21:42:06 Post No.949145 [Report]

>>949144
Like >>949139 hints at, try adding a 0,1 ohm resistor between the caps and the rectifier to simulate trace/wire resistance. Alternatively, a 0,1 ohm resistor in series with the output of the transformer. Or both.