IEEE Electrification Magazine - June 2016 - 59

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a silicon-controlled rectifier (SCR) (S 1) and coupled
inductor. The principle of operation can be described as
follows. At start-up, S1 is gated on and the capacitor (C)
is charged from the source through the coupled
inductor with the charging resistor (R). At this time,
the source supplies the load through the coupled
inductor and S1. Once the steady state is reached, the
gate signal is removed from S 1. A fault at the load
causes the capacitor to discharge through diode (D2)
and the secondary side of the coupled inductor. This
transient discharge current naturally reflects back to
the source by the turns ratio N2/N1. That is, the working
aspect of the coupled inductor is such that when the
breaker output current (i o ) rises due to a fault, the
source current (is) decreases. These laboratory measurements are shown in Figure 2. In this setup, the initial
source and load current are 6A when a short-circuit is
applied at the load side. As can be seen, the breaker output current can go up to nearly 100A. The source current rapidly responds by going to zero, and
the S1 switches off. The capacitance then
resonates with the coupled inductance,
but this is stopped by the diode (D1). The
coupled-inductor dc breaker has an automatic and rapid response to a fault. Additionally, the source does not experience the fault
current. The amount of transient current that will
switch off the breaker can be set using the turns ratio of
the coupled inductor. Another mode of operation for the
coupled-inductor breaker is as a dc switch. Any time the
source is supplying the load, the breaker can be purposefully switched off by gating S 2. This causes the
capacitor to discharge through the secondary of the
coupled-inductor and S 2. As with the fault, this discharge current causes S1 to switch off.

Bidirectional Coupled-Inductor DC Breaker
Figure 3 shows a version of the coupled-inductor dc
breaker that is capable of bidirectional power flow. It
contains a center-tapped transformer as well as
IEEE Electrific ation Magazine / j une 2 0 1 6

59



Table of Contents for the Digital Edition of IEEE Electrification Magazine - June 2016

IEEE Electrification Magazine - June 2016 - Cover1
IEEE Electrification Magazine - June 2016 - Cover2
IEEE Electrification Magazine - June 2016 - 1
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IEEE Electrification Magazine - June 2016 - Cover3
IEEE Electrification Magazine - June 2016 - Cover4
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http://www.nxtbook.com/nxtbooks/pes/electrification_september2019
http://www.nxtbook.com/nxtbooks/pes/electrification_june2019
http://www.nxtbook.com/nxtbooks/pes/electrification_march2019
http://www.nxtbook.com/nxtbooks/pes/electrification_december2018
http://www.nxtbook.com/nxtbooks/pes/electrification_september2018
http://www.nxtbook.com/nxtbooks/pes/electrification_june2018
http://www.nxtbook.com/nxtbooks/pes/electrification_december2017
http://www.nxtbook.com/nxtbooks/pes/electrification_september2017
http://www.nxtbook.com/nxtbooks/pes/electrification_march2018
http://www.nxtbook.com/nxtbooks/pes/electrification_june2017
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http://www.nxtbook.com/nxtbooks/pes/electrification_september2016
http://www.nxtbook.com/nxtbooks/pes/electrification_december2015
http://www.nxtbook.com/nxtbooks/pes/electrification_march2016
http://www.nxtbook.com/nxtbooks/pes/electrification_march2015
http://www.nxtbook.com/nxtbooks/pes/electrification_june2015
http://www.nxtbook.com/nxtbooks/pes/electrification_september2015
http://www.nxtbook.com/nxtbooks/pes/electrification_march2014
http://www.nxtbook.com/nxtbooks/pes/electrification_june2014
http://www.nxtbook.com/nxtbooks/pes/electrification_september2014
http://www.nxtbook.com/nxtbooks/pes/electrification_december2014
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