What is an Electro-mechanical/solid state tap changer?
A. In electro-mechanical devices in which regulation is achieved by selecting one of a number of tapping of a transformer, by means of relays. They usually reduce input voltage variations of 15% to 6% of constant load. Load variations will degrade this accuracy to about 10%. However, the physical mechanics of the relays result in spurious switching and possible relay failure. Solid state tap changers use triacs in series with the taps of a transformer. Eight or more triacs may be used; however spurious transients entering the tap changer can cause two triacs to fire simultaneously and this, with over current or over voltage, can cause the triacs to fail. The incorporation of isolation and surge protection into tap changers results in this type of device being called a power line conditioner or an electronics line conditioner.
