The main supply transformer is specified in a way that the supply reactant works as a limiting factor of peak asymmetric fault current; and non-compliance with this specification can be destructive for Rectifier semi-conductor devices. Over current protection is provided. Line current measuring CT’s are constantly measuring the line input current and this information is fed to trip section of control card. Where a reference is set.
The moment actual current exceeds the reference current, electronics on trip section of control card shuts off the rectifier driver PCB via sequence section of control card. This is an extremely fast protection. Over frequency protection is provided. A feedback from step-down Transformer, connected to MF AC output is fed to crowbar memory section of control card, which constantly monitors the width of AC output cycles. As soon as the width of any AC output cycle goes below a reference width (as set in Crowbar section through a mono-stable) the electronics on this section operates to shut-off rectifier.