Question

describe the symptoms that would result if one of the diodes in the bridge rectifier failed by becoming an open circuit. What symptoms would result if it failed by becoming a short circuit?

Answer 1

If one of the diode (D1) is shorted by connecting a wire parallel to it, then no current will flow through this diode during positive half cycle (when D1 and D3 operate).

Here consider a diagram

During other half cycle (when D2 and D4 operate) , two diodes will conduct and due to this, load resistance (RL) will get shorted.

due to this, the AC source will see short circuit. so large amount of current will flow through diode D3 and D4 and no current will flow through load resistance.

As there will be no voltage drop across Load Resistance therefore output will be zero during negative half cycle (when D2 and D4 operate) due to which circuit will act as a Half Wave Rectifier Circuit and due to very low impedance large amount of current will flow through diode which results in excess heating of diode