Inductors

[robbietan]

It seems that inductors are manufactured either as 3% or 5%. Why is this so?

 

[bphgravity]

Perhaps for the ease of production, standardization, reduction of costs, and ease of compatibility?

 

[robbietan]

all I can search is that line inductors are a replacement for isolation transformers. is the 3% or 5% rating somehow related to the impedance of isolation transformers?

 

[petersonra]

line reactors increase the source impedance. this reduces the maximum current flow through the semiconductors in the event of of short circuit.

 

[robbietan]

sir petersonra, that is what I thought. however, I cannot seem to find a rationale (even in the Web) as to how/why a 3% value reactance came to be a standard for line inductor manufacturers. and how a 3% additional impedance can protect against current surges.