FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
SHORT CIRCUIT DETERMINATION DEVICE, ELECTRONIC APPARATUS, AND
SHORT CIRCUIT DETERMINATION METHOD
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION
ORGANISED AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE
ADDRESS IS 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 1008310,
JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED
2
DESCRIPTION
Technical Field
[0001] The present disclosure relates to a short circuit determining device, an
electronic apparatus, and a method of determining a short circuit.5
Background Art
[0002] Electric railway vehicles of an AC feeding system include a transformer that
transforms the voltage of AC power fed from a substation via an overhead wire into a
desired voltage value, and a power conversion apparatus that converts the AC power after
voltage transformation by the transformer into desired AC power and feeds the converted10
AC power to a load device. Examples of such a transformer and a power conversion
apparatus to be installed in an electric railway vehicle are disclosed in Patent Literature 1.
Citation List
Patent Literature
[0003] Patent Literature 1: Unexamined Japanese Patent Application Publication15
No. H6-141404
Summary of Invention
Technical Problem
[0004] Patent Literature 1 discloses an electric vehicle control apparatus that
includes a transformer, a power conversion device, and a protection circuit for protecting20
circuitry. The protection circuit includes means for detecting a circuit ground fault,
which is connected to the ground terminal of the transformer and the connecting point
between the converter and the inverter of the power conversion device. This means for
detecting a circuit ground fault can detect a ground fault occurring at a position other than
the predetermined ground point in the circuitry of the electric vehicle control apparatus,25
but cannot detect abnormalities, such as a short circuit in the secondary winding of the
transformer, other than the ground fault.
3
[0005] An objective of the present disclosure, which has been accomplished in
view of the above situations, is to provide a short circuit determining device, an electronic
apparatus, and a method of determining a short circuit that can achieve determination of
whether a short circuit occurs in a secondary winding of a transformer.
Solution to Problem5
[0006] In order to achieve the above objective, a short circuit determining device
according to the present disclosure includes a first current acquirer, a second current
acquirer, and a short circuit determiner. The first current acquirer acquires a first current
value, which is a value of current flowing into a primary winding of a transformer. The
transformer transforms a voltage of AC power fed to the primary winding and outputs the10
AC power after voltage transformation from one or more secondary windings of the
transformer. The second current acquirer acquires a second current value, which is a
value of current flowing from each of the one or more secondary windings. The short
circuit determiner determines, based on the first current value and a second current value
referred to a primary side, or a first current value referred to a secondary side and the15
second current value, whether a short circuit occurs in each of the one or more secondary
windings. The second current value referred to the primary side and the first current
value referred to the secondary side are calculated from the first current value, the second
current value, the number of turns of the primary winding, and the number of turns of
each of the one or more secondary windings.20
Advantageous Effects of Invention
[0007] The present disclosure can achieve determination of whether a short circuit
occurs in the secondary winding, on the basis of the first current value and the second
current value referred to the primary side, or the first current value referred to the
secondary side and the second current value, which are calculated from the first current25
value, the second current value, the number of turns of the primary winding, and the
number of turns of the secondary winding.
4
Brief Description of Drawings
[0008] FIG. 1 is a block diagram illustrating a short circuit determining device and
a power conversion apparatus according to Embodiment 1;
FIG. 2 illustrates an exemplary flow of current in the case of a short circuit in a
secondary winding of a transformer in Embodiment 1;5
FIG. 3 illustrates hardware components of the short circuit determining device
according to Embodiment 1;
FIG. 4 is a flowchart illustrating a short circuit determining process executed by
the short circuit determining device according to Embodiment 1;
FIG. 5 is a block diagram illustrating a short circuit determining device and a10
power conversion apparatus according to Embodiment 2;
FIG. 6 is a flowchart illustrating a short circuit determining process executed by
the short circuit determining device according to Embodiment 2; and
FIG. 7 illustrates a modification of the hardware components of the short circuit
determining device according to the embodiments.15
Description of Embodiments
[0009] A short circuit determining device, an electronic apparatus, and a method of
determining a short circuit according to some embodiments of the present disclosure are
described in detail below, with reference to the accompanying drawings. In the
drawings, the components identical or corresponding to each other are provided with the20
same reference symbol.
[0010] Embodiment 1
A typical example of an electronic apparatus installed in a railway vehicle is a
power conversion apparatus installed in a railway vehicle to convert electric power fed
from a power source into AC power to be fed to a load device and feed the converted AC25
power to a motor. A power conversion apparatus 1 illustrated in FIG. 1 is installed in a
railway vehicle of an AC feeding system. The railway vehicle of an AC feeding system
5
is provided with, as well as the power conversion apparatus 1, a transformer 20 that
transforms the voltage of AC power fed from a power source 91 and feeds the AC power
after voltage transformation to the power conversion apparatus 1.
[0011] The power conversion apparatus 1 converts the AC power, fed from the
power source 91 via a circuit breaker 92 and transformed by the transformer 20, into AC5
power to be fed to a load device, specifically, a motor 93, and feeds the converted AC
power to the motor 93. A typical example of the motor 93 is a three-phase induction
motor for generating propulsion force of the railway vehicle. The power conversion
apparatus 1 includes a short circuit determining device 31 that determines whether a short
circuit occurs in the transformer 20. In response to a short circuit in the transformer 20,10
the power conversion apparatus 1 opens the circuit breaker 92 and thus electrically
disconnects the transformer 20 from the power source 91.
[0012] The power source 91 is installed in the railway vehicle. A typical example
of the power source 91 is a current collector that acquires AC power from the substation
via a power supply line. The current collector is a pantograph or a contact shoe, for15
example. The power supply line is an overhead wire or a third rail, for example.
[0013] The electrical path between the power source 91 and the transformer 20 is
provided with a circuit breaker 92 that electrically connects or disconnects the
transformer 20 to or from the power source 91. The circuit breaker 92 is closed or
opened by the power conversion apparatus 1 or a circuit breaker controller, which is not20
illustrated. The circuit breaker 92 when closed electrically connects the transformer 20
to the power source 91. The circuit breaker 92 when opened electrically disconnects the
transformer 20 from the power source 91.
[0014] The transformer 20 includes a primary winding 21 electrically connected to
the power source 91 via the circuit breaker 92, and a secondary winding 22 electrically25
connected to the electronic apparatus, specifically, the power conversion apparatus 1.
The transformer 20 transforms the voltage of AC power fed from the power source 91 to
6
the primary winding 21 via the circuit breaker 92, and outputs the AC power after voltage
transformation from the secondary winding 22 to the power conversion apparatus 1.
[0015] One end of the primary winding 21 is electrically connected to the circuit
breaker 92. The other end of the primary winding 21 is grounded via a component, such
as ground ring, ground brush, or wheel, which is not illustrated.5
[0016] One end of the secondary winding 22 is electrically connected to one of the
primary terminals of a power conversion circuit 11 included in the power conversion
apparatus 1. The other end of the secondary winding 22 is electrically connected to the
other of the primary terminals of the power conversion circuit 11.
[0017] The power conversion apparatus 1 is electrically connected to the secondary10
winding 22. The power conversion apparatus 1 converts the AC power output from the
secondary winding 22 into electric power to be fed to the load device, specifically, the
motor 93, and feeds the converted electric power to the motor 93.
[0018] The power conversion apparatus 1 includes the power conversion circuit 11
of which the primary terminals are electrically connected to the secondary winding 2215
and the secondary terminals are electrically connected to the motor 93, a circuit controller
12 that controls the power conversion circuit 11, the short circuit determining device 31
that determines whether a short circuit occurs in the secondary winding 22, and a circuit
protector 13 that electrically disconnects the primary winding 21 from the power source
91 when a short circuit is determined to occur in the secondary winding 22.20
[0019] The power conversion circuit 11 converts the AC power fed from the
secondary winding 22 via the primary terminals into three-phase AC power to be fed to
the motor 93, and then feeds the three-phase AC power from the secondary terminals to
the motor 93. For example, the power conversion circuit 11 includes a converter that
converts the AC power fed from the secondary winding 22 into DC power and outputs25
the DC power, a capacitor charged with the DC power output from the converter, and an
inverter that converts the DC power fed from the converter via the capacitor into
7
three-phase AC power.
[0020] Each of the converter and the inverter includes multiple switching elements,
such as insulated gate bipolar transistors (IGBTs), gate turn-off thyristors (GTOs), or
metal-oxide-semiconductor field-effect transistors (MOSFETs). The switching
elements perform switching operations and thus allow the converter and the inverter to5
perform power conversion.
[0021] The circuit controller 12 controls the switching elements included in the
power conversion circuit 11, in accordance with an operation command for the railway
vehicle acquired from a cab, which is not illustrated, and a result of determination by the
short circuit determining device 31. For example, the circuit controller 12 transmits10
pulse width modulation (PWM) signals to the individual gate terminals of the IGBTs of
the converter and the inverter and thus controls the IGBTs.
[0022] During running of the railway vehicle, the circuit controller 12 controls the
power conversion circuit 11 in accordance with an operation command. The circuit
controller 12, when receiving a result of determination indicating the occurrence of a15
short circuit in the transformer 20 from the short circuit determining device 31, stops the
power conversion circuit 11.
[0023] The circuit protector 13 controls the circuit breaker 92, in accordance with a
result of determination by the short circuit determining device 31. In detail, the circuit
protector 13 maintains the circuit breaker 92 to be closed, while the short circuit20
determining device 31 keeps determining that no short circuit occurs in the secondary
winding 22. When the short circuit determining device 31 determines that a short
circuit occurs in the secondary winding 22, the circuit protector 13 opens the circuit
breaker 92 and electrically disconnects the primary winding 21 of the transformer 20
from the power source 91.25
[0024] The short circuit determining device 31 includes a first current acquirer 32
that acquires a first current value, which is a value of current flowing into the primary
8
winding 21, and a second current acquirer 33 that acquires a second current value, which
is a value of current flowing from the secondary winding 22. The short circuit
determining device 31 further includes a short circuit determiner 34 that determines
whether a short circuit occurs in the secondary winding 22, on the basis of the first
current value, the second current value, the number of turns of the primary winding 21,5
and the number of turns of the secondary winding 22.
[0025] The first current acquirer 32 measures a first current value, which is a value
of current flowing in the electrical path between the power source 91 and the primary
winding 21. In detail, the first current acquirer 32 measures a first current value, with a
current-transformer (CT) type current sensor CT1 provided to the conductor that connects10
the circuit breaker 92 to the one end of the primary winding 21.
[0026] The second current acquirer 33 measures a second current value, which is a
value of current flowing in the electrical path between the secondary winding 22 and the
electronic apparatus, specifically, the power conversion apparatus 1. In detail, the
second current acquirer 33 measures a second current value, with a CT type current15
sensor CT2 provided to the conductor that connects one end of the secondary winding 22
to one of the primary terminals of the power conversion circuit 11.
[0027] The short circuit determiner 34 determines whether a short circuit occurs in
the secondary winding 22, on the basis of the first current value and a second current
value referred to the primary side, or a first current value referred to the secondary side20
and the second current value, which are calculated from the first current value, the second
current value, and the turn ratio of the transformer 20. The short circuit determiner 34 is
assumed to preliminarily retain information on the turn ratio of the transformer 20.
[0028] As an exemplary abnormality in the secondary winding 22, the conductor
that connects the one end of the secondary winding 22 to the power conversion circuit 1125
may be electrically connected directly to the conductor that connects the other end of the
secondary winding 22 to the power conversion circuit 11, for example. This direct
9
connection causes current to flow through a closed circuit defined through the secondary
winding 22, for example, as illustrated by the solid-line arrow in FIG. 2. In the case of a
short circuit at a position closer to the secondary winding 22 than the current sensor CT2,
no current flows in the current sensor CT2, so that the second current value to be acquired
by the second current acquirer 33 is sufficiently smaller than that in the case of no short5
circuit in the secondary winding 22.
[0029] Because of such a small second current value in the case of a short circuit in
the secondary winding 22 described above, the short circuit determiner 34 in
Embodiment 1 determines whether a short circuit occurs in the secondary winding 22, on
the basis of the difference between the first current value and the second current value10
referred to the primary side, specifically, the current value on the primary side of the
transformer 20 calculated from the second current value. When the absolute value of
the difference between the first current value and the current value on the primary side of
the transformer 20 calculated from the second current value is at least a first threshold, a
short circuit is deemed to occur in the secondary winding 22. In contrast, when the15
absolute value of the difference between the first current value and the current value on
the primary side of the transformer 20 calculated from the second current value is smaller
than the first threshold, no short circuit is deemed to occur in the secondary winding 22.
The first threshold is defined in accordance with a possible range of amplitude of current
flowing into the primary winding 21. For example, the first threshold is a value20
calculated by multiplying the lower limit of the possible range of amplitude of current
flowing into the primary winding 21 by a positive coefficient smaller than 1, for example,
0.5. The short circuit determiner 34 is assumed to preliminarily retain information on
the first threshold.
[0030] FIG. 3 illustrates hardware components of the short circuit determining25
device 31 having the above-described configuration. The short circuit determining
device 31 includes a processor 81, a memory 82, and an interface 83. The processor 81,
10
the memory 82, and the interface 83 are connected to each other via buses 80. The
functions of the short circuit determining device 31 are implemented by software,
firmware, or a combination of software and firmware. The software and firmware are
described in the form of programs, and stored in the memory 82. The processor 81
reads and executes the programs stored in the memory 82, and thus achieves the5
above-described functions of the components. In other words, the memory 82 stores
programs for executing the processing of the components of the short circuit determining
device 31.
[0031] Examples of the memory 82 include non-volatile or volatile semiconductor
memories, such as random access memory (RAM), read-only memory (ROM), flash10
memory, erasable programmable read-only memory (EPROM), and electrically erasable
and programmable read-only memory (EEPROM), magnetic disks, flexible disks, optical
disks, compact discs, mini discs, and digital versatile discs (DVDs).
[0032] The short circuit determining device 31 is connected to the current sensors
CT1 and CT2, the circuit controller 12, and the circuit protector 13 via the interface 83.15
The interface 83 includes interface modules compliant with one or more standards as
appropriate for connection destinations.
[0033] The short circuit determining device 31 having the above-described
configuration executes a short circuit determining process, which is described below with
reference to FIG. 4. In response to start of running of the railway vehicle and closing of20
the circuit breaker 92, the short circuit determining device 31 initiates the process
illustrated in FIG. 4.
[0034] The first current acquirer 32 acquires a first current value, which is a value
of current flowing into the primary winding 21, and the second current acquirer 33
acquires a second current value, which is a value of current flowing from the secondary25
winding 22 (Step S11).
[0035] The short circuit determiner 34 calculates a difference ΔD1 between the first
11
current value IP and the current value on the primary side of the transformer 20 calculated
from the second current value IS1, using Expression (1) below (Step S12). In detail, the
short circuit determiner 34 subtracts the product of the second current value IS1 and the
inverse of the turn ratio NP/NS1 of the transformer 20, from the first current value IP, and
thus calculates a difference ΔD1.5
[0036] Expression 1
[0037] The short circuit determiner 34 determines whether the absolute value of the
difference ΔD1 calculated in Step S12 is at least the first threshold (Step S13). When
the absolute value of the difference ΔD1 calculated in Step S12 is at least the first10
threshold (Step S13; Yes), the short circuit determiner 34 outputs a result of
determination indicating the occurrence of a short circuit, to the circuit controller 12 and
the circuit protector 13 (Step S14). In response to this result, the circuit controller 12
stops the power conversion circuit 11, and the circuit protector 13 opens the circuit
breaker 92. This operations causes the transformer 20, of which the secondary winding15
22 has a short circuit, to be electrically disconnected from the power source 91. After
Step S14, the short circuit determining device 31 repeats Step S11 and the subsequent
steps described above.
[0038] In contrast, when the absolute value of the difference ΔD1 calculated in Step
S12 is smaller than the first threshold (Step S13; No), the short circuit determiner 3420
outputs a result of determination indicating no short circuit, to the circuit controller 12
and the circuit protector 13 (Step S15). In response to this result, the circuit controller
12 continues to operate the power conversion circuit 11 in accordance with an operation
command. The circuit protector 13 does not open the circuit breaker 92, and maintains
the circuit breaker 92 to be closed. After Step S15, the short circuit determining device25
31 repeats Step S11 and the subsequent steps described above.
12
[0039] As described above, the short circuit determining device 31 according to
Embodiment 1 can determine whether a short circuit occurs in the secondary winding 22
of the transformer 20, on the basis of the first current value and the second current value
referred to the primary side, which are calculated from the first current value, the second
current value, and the turn ratio of the transformer 20.5
[0040] Embodiment 2
The configuration of the transformer 20 in Embodiment 1 is a mere example.
The transformer 20 may include multiple secondary windings, for example. The
configuration of the short circuit determining device 31 in Embodiment 1 is a mere
example. The short circuit determining device 31 may open the circuit breaker 92.10
The description of Embodiment 2 demonstrates the transformer 20 and the short circuit
determining device 31 having a configuration different from that in Embodiment 1,
focusing on the differences from Embodiment 1.
[0041] As illustrated in FIG. 5, the transformer 20 in Embodiment 2 includes a
primary winding 21, and multiple secondary windings, specifically, secondary windings15
22 and 23. The secondary winding 22 is electrically connected to a power conversion
apparatus 1, as in Embodiment 1. The secondary winding 23 is electrically connected to
a power conversion apparatus 2. The transformer 20 transforms the voltage of AC
power fed from the power source 91 to the primary winding 21 via the circuit breaker 92,
and outputs the AC power after voltage transformation from the secondary winding 22 to20
the power conversion apparatus 1, and outputs the AC power after voltage transformation
from the secondary winding 23 to the power conversion apparatus 2.
[0042] The power conversion apparatus 2 converts the AC power, fed from the
power source 91 via the circuit breaker 92 and transformed by the transformer 20, into
AC power to be fed to a load device, specifically, a motor 94, and feeds the converted AC25
power to the motor 94. A typical example of the motor 94 is a three-phase induction
motor for generating propulsion force of the railway vehicle.
13
[0043] The power conversion apparatus 2 includes a power conversion circuit 14 of
which the primary terminals are electrically connected to the secondary winding 23 and
the secondary terminals are electrically connected to the motor 94, and a circuit controller
15 that controls the power conversion circuit 14.
[0044] The power conversion circuit 14 converts the AC power fed from the5
secondary winding 23 via the primary terminals into three-phase AC power to be fed to
the motor 94, and then feeds the three-phase AC power from the secondary terminals to
the motor 94. For example, the power conversion circuit 14 includes a converter that
converts the AC power fed from the secondary winding 23 into DC power and outputs
the DC power, a capacitor charged with the DC power output from the converter, and an10
inverter that converts the DC power fed from the converter via the capacitor into
three-phase AC power.
[0045] Each of the converter and the inverter includes multiple switching elements,
such as IGBTs, GTOs, or MOSFETs. The switching elements perform switching
operations and thus allow the converter and the inverter to perform power conversion.15
[0046] The circuit controller 15 controls the switching elements included in the
power conversion circuit 14, in accordance with an operation command for the railway
vehicle acquired from the cab and a result of determination by the short circuit
determining device 31. For example, the circuit controller 15 transmits PWM signals to
the individual gate terminals of the IGBTs of the converter and the inverter and thus20
controls the IGBTs.
[0047] During running of the railway vehicle, the circuit controller 15 controls the
power conversion circuit 14 in accordance with an operation command. The circuit
controller 15, when receiving a result of determination indicating the occurrence of a
short circuit in the transformer 20 from the short circuit determining device 31, stops the25
power conversion circuit 14.
[0048] The power conversion apparatuses 1 and 2 both exclude the short circuit
14
determining device 31 and the circuit protector 13, unlike the power conversion apparatus
1 according to Embodiment 1.
[0049] In Embodiment 2, the short circuit determining device 31 is an independent
device separate from the power conversion apparatuses 1 and 2. The second current
acquirer 33 of the short circuit determining device 31 acquires second current values,5
which are values of current flowing from the respective secondary windings 22 and 23.
In other words, the second current acquirer 33 measures a second current value of the
secondary winding 22, which is a value of current flowing in the electrical path between
the secondary winding 22 and the power conversion circuit 11, and a second current
value of the secondary winding 23, which is a value of current flowing in the electrical10
path between the secondary winding 23 and the power conversion circuit 14.
[0050] In detail, the second current acquirer 33 measures second current values of
the secondary windings 22 and 23, with a CT type current sensor CT2 provided to the
conductor that connects one end of the secondary winding 22 to one of the primary
terminals of the power conversion circuit 11, and a CT type current sensor CT3 provided15
to the conductor that connects one end of the secondary winding 23 to one of the primary
terminals of the power conversion circuit 14.
[0051] The short circuit determiner 34 determines whether a short circuit occurs in
the secondary windings 22 and 23, on the basis of the first current value and second
current values referred to the primary side, which are calculated from the first current20
value, the second current value, the number of turns of the primary winding 21, and the
numbers of turns of the respective secondary windings 22 and 23. The short circuit
determiner 34 is assumed to preliminarily retain information on the number of turns of
the primary winding 21 and the numbers of turns of the respective secondary windings 22
and 23.25
[0052] As an exemplary abnormality, a short circuit may occur in at least either of
the secondary windings 22 and 23. For example, a short circuit may occur in the
15
secondary winding 22, specifically, the conductor that connects the one end of the
secondary winding 22 to the one of the primary terminals of the power conversion circuit
11 may be electrically connected directly to the conductor that connects the other end of
the secondary winding 22 to the other of the primary terminals of the power conversion
circuit 11. This direct connection causes current to flow through a closed circuit defined5
through the secondary winding 22. In the case of a short circuit at a position closer to
the secondary winding 22 than the current sensor CT2, no current flows in the current
sensor CT2, so that the second current value of the secondary winding 22 to be acquired
by the second current acquirer 33 is sufficiently smaller than that in the case of no short
circuit in the secondary winding 22.10
[0053] For another example, a short circuit may occur in the secondary winding 23,
specifically, the conductor that connects the one end of the secondary winding 23 to the
power conversion circuit 14 may be electrically connected directly to the conductor that
connects the other end of the secondary winding 23 to the power conversion circuit 14.
This direct connection causes current to flow through a closed circuit defined through the15
secondary winding 23. In the case of a short circuit at a position closer to the secondary
winding 23 than the current sensor CT3, no current flows in the current sensor CT3, so
that the second current value of the secondary winding 23 to be acquired by the second
current acquirer 33 is sufficiently smaller than that in the case of no short circuit in the
secondary winding 23.20
[0054] Because of such a small sum of second current values in the case of a short
circuit in at least either of the secondary windings 22 and 23 described above, the short
circuit determiner 34 determines whether a short circuit occurs in at least either of the
secondary windings 22 and 23, on the basis of the difference between the first current
value and the second current values referred to the primary side, specifically, current25
values on the primary side of the transformer 20 calculated from the second current
values. When the absolute value of the difference between the first current value and
16
the current value on the primary side of the transformer 20 calculated from the second
current values is at least the first threshold, a short circuit is deemed to occur in at least
either of the secondary windings 22 and 23. In contrast, when the absolute value of the
difference between the first current value and the current value on the primary side of the
transformer 20 calculated from the second current values is smaller than the first5
threshold, no short circuit is deemed to occur in the secondary windings 22 and 23.
[0055] The short circuit determining device 31 also includes, in addition to the
components of the short circuit determining device 31 according to Embodiment 1, a
circuit protector 35 that controls the circuit breaker 92. The circuit protector 35 closes
or opens the circuit breaker 92, in accordance with a result of determination by the short10
circuit determiner 34. In detail, the circuit protector 35 maintains the circuit breaker 92
to be closed, while the short circuit determiner 34 keeps determining that no short circuit
occurs in the secondary windings 22 and 23. When the short circuit determiner 34
determines that a short circuit occurs in at least either of the secondary windings 22 and
23, the circuit protector 35 opens the circuit breaker 92 and electrically disconnects the15
primary winding 21 of the transformer 20 from the power source 91.
[0056] The short circuit determining device 31 has the hardware components
identical to those in Embodiment 1, except for the connection destinations via the
interface 83. In Embodiment 2, the interface 83 is connected to the current sensors CT1,
CT2, and CT3 and the circuit controllers 12 and 15.20
[0057] The short circuit determining device 31 having the above-described
configuration executes a short circuit determining process, which is described below with
reference to FIG. 6. In response to start of running of the railway vehicle and closing of
the circuit breaker 92, the short circuit determining device 31 initiates the process
illustrated in FIG. 6.25
[0058] The first current acquirer 32 acquires a first current value, which is a value
of current flowing into the primary winding 21, and the second current acquirer 33
17
acquires second current values, which are values of current flowing from the respective
secondary windings 22 and 23 (Step S21).
[0059] The short circuit determiner 34 calculates a difference ΔD2 between the first
current value and the current value on the primary side of the transformer 20 calculated
from the second current value, using the Expression (2) below (Step S22). In detail, the5
short circuit determiner 34 subtracts the sum of the second current value IS1 multiplied by
the number NS1 of turns of the secondary winding 22 and divided by the number NP of
turns of the primary winding 21 and the second current value IS2 multiplied by the
number of turns NS2 of the secondary winding 23 and divided by the number NP of turns
of the primary winding 21, from the first current value IP, and thus calculates a difference10
ΔD2. The second current value IS1 indicates a value of current flowing from the
secondary winding 22, and the second current value IS2 indicates a value of current
flowing from the secondary winding 23.
[0060] Expression 2
15
[0061] The short circuit determiner 34 determines whether the absolute value of the
difference ΔD2 calculated in Step S22 is at least the first threshold (Step S23). When
the absolute value of the difference ΔD2 calculated in Step S22 is at least the first
threshold (Step S23; Yes), the short circuit determiner 34 outputs a result of
determination indicating the occurrence of a short circuit, to the circuit controllers 12 and20
15 and the circuit protector 35 (Step S24). In response to this result, the circuit
controllers 12 and 15 stop the power conversion circuits 11 and 14.
[0062] The circuit protector 35, when receiving a result of determination indicating
the occurrence of a short circuit, opens the circuit breaker 92 (Step S25). After Step S25,
the short circuit determining device 31 repeats Step S21 and the subsequent steps25
18
described above.
[0063] In contrast, when the absolute value of the difference ΔD2 calculated in Step
S22 is smaller than the first threshold (Step S23; No), the short circuit determiner 34
outputs a result of determination indicating no short circuit, to the circuit controllers 12
and 15 and the circuit protector 35 (Step S26). In response to this result, the circuit5
controllers 12 and 15 continue to operate the power conversion circuits 11 and 14 in
accordance with an operation command. The circuit protector 35 skips Step S25,
specifically, does not open the circuit breaker 92, and maintains the circuit breaker 92 to
be closed. After Step S26, the short circuit determining device 31 repeats Step S21 and
the subsequent steps described above.10
[0064] As described above, the short circuit determining device 31 according to
Embodiment 2 can determine whether a short circuit occurs in the secondary windings 22
and 23, on the basis of the first current value, the second current value, the number of
turns of the primary winding 21, and the numbers of turns of the respective secondary
windings 22 and 23, and can electrically disconnect the transformer 20 from the power15
source 91 in the case of a short circuit in the secondary winding 22 or 23.
[0065] The above-described embodiments of the present disclosure are mere
examples. The power conversion apparatuses 1 and 2 can be installed in any vehicle or
apparatus in which the power conversion apparatuses 1 and 2 are fed with electric power.
The power conversion apparatuses 1 and 2 can also be installed in vehicles, such as diesel20
vehicles, other than the electric railway vehicle.
[0066] The transformer 20 may have a configuration other than that in the
above-described examples. The transformer 20 may include any number of secondary
windings. The secondary windings included in the transformer 20 may have the same
number of turns or different number of turns.25
[0067] The short circuit determining process executed by the short circuit
determiner 34 may be a process other than those in the above-described examples. For
19
example, the short circuit determiner 34 may determine whether a short circuit occurs in
the secondary winding 22, on the basis of a first current value referred to the secondary
side and the second current value. In detail, the short circuit determiner 34 may
calculate a difference ΔD1’ between a current value on the secondary side of the
transformer 20 calculated from the first current value IP and the second current value IS1,5
using Expression (3) below. In detail, the short circuit determiner 34 may subtract the
second current value IS1 from the product of the first current value IP and the turn ratio
NP/NS1 of the transformer 20, and thus calculate a difference ΔD1’.
[0068] Expression 3
10
[0069] In this case, the short circuit determiner 34 determines whether the absolute
value of the difference ΔD1’ is at least a second threshold. The second threshold is
defined in accordance with a possible range of amplitude of current flowing from the
secondary winding 22. For example, the second threshold is a value calculated by
multiplying the lower limit of the possible range of amplitude of current flowing from the15
secondary winding 22 by a positive coefficient smaller than 1, for example, 0.5. The
short circuit determiner 34 is assumed to preliminarily retain information on the second
threshold.
[0070] In another exemplary case where multiple secondary windings included in
the transformer 20 have the same number of turns, the short circuit determiner 34 of the20
short circuit determining device 31 according to Embodiment 2 may determine whether a
short circuit occurs in each of the secondary windings, on the basis of the first current
value, the second current value, the number of turns of the primary winding 21, and the
number of turns of the secondary winding.
[0071] In detail, the short circuit determiner 34 calculates a difference ΔD3 between25
20
the first current value and a current value on the primary side of the transformer 20
calculated from each of the second current values, using Expression (4) below. In
Expression (4) below, M indicates the number of secondary windings included in the
transformer 20, and NS indicates the number of turns of the secondary winding. k
indicates a natural number equal to or larger than 1 and equal to or smaller than M, and5
ISk indicates a second current value, which is a value of current flowing from each of the
secondary windings.
[0072] Expression 4
[0073] The short circuit determiner 34 calculates a difference ΔD3 for each of the10
secondary windings, and determines whether the absolute value of the difference ΔD3 is
at least the first threshold. When the absolute value of the difference ΔD3 is at least the
first threshold in either of the secondary windings, a short circuit is deemed to occur in
this secondary winding.
[0074] Alternatively, the short circuit determiner 34, when determining that a short15
circuit occurs in at least any of the secondary windings, may determine whether a short
circuit occurs in each of the secondary windings, on the basis of the second current values
of the secondary windings. Specifically, the short circuit determiner 34 may determine
whether the second current value of each of the secondary windings has an amplitude
falling within a range of values sufficiently low to be deemed 0. In the case of a short20
circuit, a current value detectable by a current sensor is sufficiently small, as described
above. The short circuit determiner 34 thus determines whether a short circuit occurs in
each of the secondary windings, on the basis of whether the second current value of each
of the secondary windings has an amplitude falling within a range of values sufficiently
low to be deemed 0.25
[0075] Alternatively, the short circuit determiner 34 may determine whether a short
21
circuit occurs in the secondary winding, on the basis of the ratio of the second current
value referred to the primary side to the original first current value, or the ratio of the first
current value referred to the secondary side to the original second current value.
Specifically, the short circuit determiner 34 may determine whether a short circuit occurs
in the secondary winding 22, on the basis of the ratio of the current value on the primary5
side of the transformer 20 calculated from the second current value to the first current
value. When the absolute value of the ratio of the current value on the primary side of
the transformer 20 calculated from the second current value to the first current value is
equal to or smaller than a third threshold, a short circuit is deemed to occur in the
secondary winding 22. The third threshold is a positive value smaller than 1, for10
example, 0.5. The short circuit determiner 34 is assumed to preliminarily retain
information on the third threshold.
[0076] Alternatively, the short circuit determiner 34 may determine whether a short
circuit occurs in the secondary winding 22, on the basis of the ratio of the current value
on the secondary side of the transformer 20 calculated from the first current value to the15
second current value. When the ratio of the current value on the secondary side of the
transformer 20 calculated from the first current value to the second current value is equal
to or smaller than the third threshold, a short circuit is deemed to occur in the secondary
winding 22.
[0077] The electronic apparatus connected to the transformer 20 is not necessarily20
the power conversion apparatus 1 or 2 and may be any electronic apparatus.
[0078] The power conversion apparatuses 1 and 2 may feed electric power to any
load device, such as lighting equipment or air conditioner, other than the motors 93 and
94.
[0079] The current sensors CT1, CT2, and CT3 may be disposed at positions other25
than those in the above-described examples. For example, the current sensor CT1 may
be provided to the conductor connected to the other end of the primary winding 21. The
22
current sensor CT2 may be provided to the conductor that connects the other end of the
secondary winding 22 to the other of the primary terminals of the power conversion
circuit 11. The current sensor CT3 may be provided to the conductor that connects the
other end of the secondary winding 23 to the power conversion circuit 14.
[0080] The first current acquirer 32 may obtain an amplitude of current flowing into5
the primary winding 21 from the measured value of current flowing into the primary
winding 21, and use this amplitude as a first current value.
[0081] The second current acquirer 33 may obtain an amplitude of current flowing
from the secondary winding 22 from the measured value of current flowing from the
secondary winding 22, and use this amplitude as a second current value of the secondary10
winding 22. The second current acquirer 33 may obtain an amplitude of current flowing
from the secondary winding 23 from the measured value of current flowing from the
secondary winding 23, and use this amplitude as a second current value of the secondary
winding 23.
[0082] Although the circuit protector 13 is included in the power conversion15
apparatus 1 in Embodiment 1, the circuit protector 13 may also be achieved as a function
of an integrated train control and monitoring device.
[0083] Although the short circuit determining device 31 is separate from the power
conversion apparatuses 1 and 2 in Embodiment 2, the short circuit determining device 31
may also be included in the power conversion apparatus 1 or 2. Alternatively, the short20
circuit determining device 31 may be achieved as a function of the train control and
monitoring device.
[0084] The short circuit determining device 31 may have hardware components
other than those in the above-described examples. The short circuit determining device
31 may be achieved by a processing circuit 84, as illustrated in FIG. 7. The processing25
circuit 84 is connected to the current sensors CT1 and CT2, the circuit controller 12, and
the circuit protector 13, via an interface circuit 85.
23
[0085] In the case where the processing circuit 84 is dedicated hardware, the
processing circuit 84 includes a single circuit, a combined circuit, a processor, an
application specific integrated circuit (ASIC), a field programmable gate array (FPGA),
or a combination thereof, for example. The individual components of the short circuit
determining device 31 may be achieved by separate processing circuits 84 or by the same5
processing circuit 84.
[0086] A part of the functions of the short circuit determining device 31 may be
performed by dedicated hardware, whereas another part of the functions may be
performed by software or firmware. For example, the first current acquirer 32 and the
second current acquirer 33 may be achieved by the processing circuit 84 illustrated in10
FIG. 7, whereas the short circuit determiner 34 may be achieved by programs stored in
the memory 82 when the programs are read and executed by the processor 81 illustrated
in FIG. 3, in the short circuit determining device 31 according to Embodiment 1.
[0087] The foregoing describes some example embodiments for explanatory
purposes. Although the foregoing discussion has presented specific embodiments,15
persons skilled in the art will recognize that changes may be made in form and detail
without departing from the broader spirit and scope of the invention. Accordingly, the
specification and drawings are to be regarded in an illustrative rather than a restrictive
sense. This detailed description, therefore, is not to be taken in a limiting sense, and the
scope of the invention is defined only by the included claims, along with the full range of20
equivalents to which such claims are entitled.
Reference Signs List
[0088] 1, 2 Power conversion apparatus
11, 14 Power conversion circuit
12, 15 Circuit controller25
13, 35 Circuit protector
20 Transformer
24
21 Primary winding
22, 23 Secondary winding
31 Short circuit determining device
32 First current acquirer
33 Second current acquirer5
34 Short circuit determiner
80 Bus
81 Processor
82 Memory
83 Interface10
84 Processing circuit
85 Interface circuit
91 Power source
92 Circuit breaker
93, 94 Motor15
CT1, CT2, CT3 Current sensor
25
We Claim:
[Claim 1] A short circuit determining device (31), comprising:
a first current acquirer (32) to acquire a first current value, the first current value
being a value of current flowing into a primary winding (21) of a transformer (20), the5
transformer (20) transforming a voltage of AC power fed to the primary winding (21) and
outputting the AC power after voltage transformation from a plurality of secondary
windings (22, 23) of the transformer (20);
a second current acquirer (33) to acquire second current values, the second current
values being values of current flowing from the plurality of secondary windings (22, 23);10
and
a short circuit determiner (34) to determine, based on the first current value and
second current values referred to a primary side, whether a short circuit occurs in at least
any of the plurality of secondary windings (22, 23), the second current values referred to
the primary side being calculated from the first current value, the second current values of15
the plurality of secondary windings (22, 23), a number of turns of the primary winding
(21), and numbers of turns of the plurality of secondary windings (22, 23), wherein
when the short circuit determiner (34) determines that a short circuit occurs in at
least any of the plurality of secondary windings (22, 23), the short circuit determiner (34)
determines, based on the second current values of the plurality of secondary windings (22,20
23), whether a short circuit occurs in each of the plurality of secondary windings (22, 23).
[Claim 2] A short circuit determining device (31), comprising:
a first current acquirer (32) to acquire a first current value, the first current value
being a value of current flowing into a primary winding (21) of a transformer (20), the25
transformer (20) transforming a voltage of AC power fed to the primary winding (21) and
outputting the AC power after voltage transformation from a plurality of secondary
26
windings (22, 23) of the transformer (20), the plurality of secondary windings (22, 23)
having a same number of turns;
a second current acquirer (33) to acquire second current values, the second current
values being values of current flowing from the plurality of secondary windings (22, 23);
and5
a short circuit determiner (34) to determine, for each of the plurality of secondary
windings (22, 23), based on the first current value and second current values referred to a
primary side, or a first current value referred to a secondary side and the second current
values, whether a short circuit occurs in at least any of the plurality of secondary
windings (22, 23), the second current values referred to the primary side and the first10
current value referred to the secondary side being calculated from the first current value,
the second current value of each of the plurality of secondary windings (22, 23), a
number of turns of the primary winding (21), and a number of turns of each of the
plurality of secondary windings (22, 23).
15
[Claim 3] The short circuit determining device (31) according to claim 1 or 2,
wherein the first current acquirer (32) measures the first current value, the first current
value being a value of current flowing in an electrical path between a power source (91)
and the primary winding (21), the power source (91) feeding electric power to the
transformer (20).20
[Claim 4] The short circuit determining device (31) according to any one of
claims 1 to 3, wherein the second current acquirer (33) measures the second current
values, the second current values being values of current flowing in electrical paths
between the plurality of secondary windings (22, 23) and corresponding electronic25
apparatuses electrically connected to the plurality of secondary winding.
27
[Claim 5] The short circuit determining device (31) according to any one of
claims 1 to 4, further comprising:
a circuit protector (35) to electrically disconnect the primary winding (21) from a
power source (91) when the short circuit determiner (34) determines that a short circuit5
occurs, the power source (91) feeding electric power to the primary winding (21) of the
transformer (20).
[Claim 6] An electronic apparatus electrically connected to any of a plurality of
secondary windings (22, 23) of a transformer (20), the transformer (20) transforming a10
voltage of AC power fed to a primary winding (21) of the transformer (20) and outputting
the AC power after voltage transformation from the plurality of secondary windings (22,
23), the electronic apparatus comprising:
the short circuit determining device (31) according to any one of claims 1 to 4 to
determine whether a short circuit occurs in at least any of the plurality of secondary15
windings (22, 23) of the transformer (20).
[Claim 7] The electronic apparatus according to claim 6, further comprising:
a circuit protector (13) to electrically disconnect the primary winding (21) from a
power source (91) when the short circuit determiner (34) determines that a short circuit20
occurs, the power source (91) feeding electric power to the primary winding (21) of the
transformer (20).
[Claim 8] An electronic apparatus, electrically connected to any of a plurality of
secondary windings (22, 23) of a transformer (20), the transformer (20) transforming a25
voltage of AC power fed to a primary winding (21) of the transformer (20) and outputting
the AC power after voltage transformation from the plurality of secondary windings (22,
28
23), the electronic apparatus comprising:
the short circuit determining device (31) according to claim 5 to determine whether
a short circuit occurs in at least any of the plurality of secondary windings (22, 23) of the
transformer (20).
5
[Claim 9 ] The electronic apparatus according to any one of claims 6 to 8, further
comprising:
a power conversion circuit (11, 14) electrically connected to any of the plurality of
secondary windings (22, 23) of the transformer (20), the power conversion circuit (11,
14) being configured to convert the AC power output from the connected one of the10
plurality of secondary windings (22, 23) into electric power to be fed to a load device,
and output the converted electric power to the load device.
[Claim 10] The electronic apparatus according to claim 9, further comprising:
a circuit controller (12, 15) configured to control the power conversion circuit (11,15
14), wherein
the circuit controller (12, 15) stops the power conversion circuit (11, 14), when the
short circuit determiner (34) determines that a short circuit occurs.
[Claim 11] A method of determining a short circuit, the method comprising:20
acquiring a first current value, the first current value being a value of current
flowing into a primary winding (21) of a transformer (20), the transformer (20)
transforming a voltage of AC power fed to the primary winding (21) and outputting the
AC power after voltage transformation from a plurality of secondary windings (22, 23) of
the transformer (20);25
acquiring second current values, the second current values being values of current
flowing from the plurality of secondary windings (22, 23);
29
determining, based on the first current value and second current values referred to a
primary side, whether a short circuit occurs in at least nay of the plurality of secondary
windings (22, 23), the second current values referred to the primary side being calculated
from the first current value, the second current values of the plurality of secondary
windings (22, 23), a number of turns of the primary winding (21), and numbers of turns5
of the plurality of secondary windings (22, 23), and
upon determining that a short circuit occurs in at least any of the plurality of
secondary windings (22, 23), determining, based on the second current values of the
plurality of secondary windings (22, 23), whether a short circuit occurs in each of the
plurality of secondary windings (22, 23).10
[Claim 12] A method of determining a short circuit, the method comprising:
acquiring a first current value, the first current value being a value of current
flowing into a primary winding (21) of a transformer (20), the transformer (20)
transforming a voltage of AC power fed to the primary winding (21) and outputting the15
AC power after voltage transformation from a plurality of secondary windings (22, 23) of
the transformer (20), the plurality of secondary windings (22, 23) having a same number
of turns;
acquiring second current values, the second current values being values of current
flowing from the plurality of secondary windings (22, 23); and20
determining, for each of the plurality of secondary windings (22, 23), based on the
first current value and second current values referred to a primary side, or a first current
value referred to a secondary side and the second current values, whether a short circuit
occurs in at least any of the plurality of secondary windings (22, 23), the second current
values referred to the primary side and the first current value referred to the secondary25
side being calculated from the first current value, the second current value of each of the
plurality of secondary windings (22, 23), a number of turns of the primary winding (21),
30
and a number of turns of each of the plurality of secondary windings (22, 23).