IEEE Electrification Magazine - September 2013 - 19

The configuration of
the pantograph has
drastically changed,
reflecting strong
demands for noise
reduction of the
pantograph.

Some manufacturers propose a
power set with an injection-enhanced
gate transistor (IEGT) or integrated
gate commutated turn-off thyristor
devices.
The HSR industry is now waiting
for new power devices with lower
loss and more switching speed than
silicon devices to reduce the weight
and size of power converters. Among
the several wide-gap devices under
development, the silicon carbide
(SiC) shot-key barrier diode might be
the closest to the application, according to the latest papers. For example, Mitsubishi Electric
reported 28% maximum improvement of total loss and
18% average improvement with 300-kW inverter set.
Besides drive systems, the rolling stock carries auxiliary
power sources of several hundred kilowatts for air conditioning and lighting for passengers and controlling and
cooling. We also have to count information processing systems, telecommunication systems, and signal systems.
Every system is full of semiconductors.

Packaging and Cooling
The packaging and cooling technique of the power circuit
is one of the key technologies of HSR. From the beginning,
each car in the trainset of Japanese Shinkansen had traction motors. This type of system is called a distributed
power train or EMU. In this case, although rated power is
smaller than concentrated type, every power component

should be set within the limited space
under the floor.
The cooling system began with
forced air driven by a blower. There are
several approaches available today,
such as forced air, heat pipes, ebullient
cooling with perfluorocarbon, natural
air, and water cooling. Figure 10 shows
the history of cooling.
In any case, all of the power components are integrated in limited space.
When engineers design the onboard propulsion system, they should carefully
consider a total balance of power flow,
thermal flow, air flow, mass balance, ease of manufacturing
and maintenance, and cost. The specification of the recent
power converter/inverter set for N700 type Shinkansen using
3,300-V, 1,200-A IGBTs with natural air flow cooling is
1,600 kW/1,320 kg.
The expected direction of future HSR improvements
might be higher speed and more comfort. Thus, expected
power devices for HSR should be higher voltage, larger
current, with faster switching and more efficient power
devices. Of course, cost is an important problem; however, the market for HSR is growing, and we can hope for
a volume efficiency effect.
Since new wide-gap power semiconductors such as SiC
or gallium nitride will improve the efficiency of onboard
power converters, trains can reduce the weight and size of
converters. For example, one of the expected applications of
an SiC device is a medium frequency propulsion convertor,

Source (Three Phase)
Source Impedance

Scott Connected Feeding Transformer

Main Phase
Bus

Main
Phase
Feeding
Circuit

Teaser Bus

Inverter

Inverter
Transformer

Teaser
Feeding
Circuit
dc Side
Capacitor

RPC

Figure 11. A railway static power conditioner (power balancer).
IEEE Elec trific ation Magazine / s ep t em be r 2 0 1 3

Table of Contents for the Digital Edition of IEEE Electrification Magazine - September 2013