This paper presents a new hybrid diverter design
for on-load tap changers. The design uses active-shunt’ current diversion principles. At its core, the design employs a low-voltage high-current switch-mode amplifier to divert current out of the
mechanical contacts and into a pair of anti-parallel thyristors.
Commutation between transformer taps may then be performed by the thyristors. The amplifier and thyristors are placed outside the normal load current path and only conduct during a tap
change, producing efficiency savings and improving robustness when compared to previous hybrid OLTC implementations. An amplifier control loop that autonomously produces zero-current
conditions at switch opening and zero-voltage conditions at switch closure is demonstrated
Experimental results investigating the wear characteristics of contacts operated under the new hybrid diverter are presented, along with comparison results from a passive-type switching scheme. Contact lifetime of over 25 million operations is demonstrated under the new scheme.