Electrical Engineering problems!!! Linear & switching mode power regulators: 1. What is the major weakness of a Buck Regulator that compared with a Linear Regulator? Is't efficiency? Passive harmonics filter: 1. If the filter reactance for harmonics is a negative value, what is the meaning behind that? Relation to direction? 2. Passive filter can provide certain capacitive compensation to the ac traction power system. However, when there is off-peak hour, very few trains running in the system. Any problem will introduced by the filter? Energy saving? Thanks.