hello everybody

how about the positioning of thyristor fuses in dc drives for single quadrant applications
1) either in the line side( we will have only three)
2)before/after thyristors( in this case we will have 6 fuses)

which type is advantageous

ram

Hello ram

It is always best to postion the protection fuses upstream of the devices that you are protecting.

There are two issues to be concerned about when applying semiconductor fuses to SCRs. The first is to ensure that the total clearing I²t is less than the maximum I²t of the SCRs, and the second is to ensure that the current carrying capacity of the fuse is higher than the maximum current that it will have to carry. i.e. during an overload or rapid acceleration.
If the current carrying capacity is well in excess of the maximum phase current, then you can fit the fuses in the incoming phases.
If the current carrying capacity is a bit marginal, then you can fit the fuses in series with each SCR. This will subject the fuse to 70% of the line current.

Best regards,
Mark.