Electric power conversion systems – Current conversion – With condition responsive means to control the output...
Reexamination Certificate
2002-05-21
2004-06-08
Patel, Rajnikant B. (Department: 2838)
Electric power conversion systems
Current conversion
With condition responsive means to control the output...
C363S097000, C318S625000, C318S566000
Reexamination Certificate
active
06747882
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electric power conversion device for variable-speed controlling of a motor driving a pump, for example and more specifically, to an electric power conversion device equipped with multiplex control units to enable it to continue controlling even if a control circuit breaks down in operation.
2. Description of the Related Art
For example, with respect to a power conversion device such as one used in a recirculation pump power equipment with variable frequency control in a nuclear power plant, generally only one control unit for controlling variable frequency is equipped with the power conversion device. That is, although a control device is composed as a single component, in an institution for which advanced reliability is required, such as a nuclear power plant, redundant dual components having both an operation system and a standby system as multiplex control units are adopted in consideration of safety.
Hereafter, a conventional example of the multiplex control units of the power conversion device is explained in reference to
FIGS. 7 through 10
. As shown in
FIG. 7
, a power conversion device
100
is connected between an AC power supply
1
and a motor
3
for driving a recirculation pump and is composed of a power converter
20
for variable-speed control of the motor
3
.
As shown in
FIG. 7
, a conventional power conversion device has multiplex control units of a power converter
20
, that is, it is composed of the power converter
20
as a control target, a control circuit A
121
and a control circuit B
122
, which are arranged dual to control the power converter
20
, a selector switch
21
for switching from one control circuit to another control circuit, and a selection circuit
22
for outputting a changeover selection signal to the selector switch
21
. When the control circuit A
121
is operating, the control circuit B
122
is a standby. An input side circuit of the power converter
20
is connected to current transformers (CT)
101
and
102
for detecting circuit current, and an output side circuit of the power converter
20
is connected to power transformers
111
and
112
, respectively. Detected outputs from the current transformer
101
and the power transformer
111
and detected outputs from the current transformer
102
and the power transformer
112
are inputted to the control circuit A
121
and the control circuit B
122
, respectively.
As shown in FIG.
8
A and
FIG. 8B
, in an ordinary state, the power converter
20
is controlled and driven by the control circuit A
121
as an operating unit (this is denoted as S
41
in FIG.
8
). When the power converter
20
works normally but the control circuit A
121
is broken for some reason (S
42
), the selection circuit
22
outputs a changeover selection signal to the selector switch
21
, and the selector switch
21
changes a contact from the control circuit A
121
to the control circuit B
122
(S
43
), and the control circuit B
122
, which was a standby equipment, starts to control the power converter
20
(S
44
), and continues the control of the power converter
20
.
Moreover, as shown in FIG.
9
A and
FIG. 9B
, in a case that the control circuit A
121
controls the power converter
20
(S
51
in
FIG. 9
) and monitors a state of the power converter
20
by receiving detected signals of circuit and voltage from the current transformer
101
and the power transformer
111
, respectively, etc., when the power converter
20
breaks down (S
52
), the control circuit A
121
detects an abnormal state of the power converter
20
(S
53
), the selector switch
21
receives a changeover selection signal outputted from the selection circuit
22
and switches a contact from the control circuit A
121
to the control circuit B
122
(S
54
). In this situation, if the control circuit B
122
also detects an abnormal state of the power converter
20
, it judges this detection as a failure of the power converter
20
and stops operation of the power converter
20
.
In the above-mentioned conventional multiplex control units of the power conversion device
2
, when the control unit A
121
in an operation has broken (from S
61
to S
62
in FIG.
10
), it is possible that the power converter
20
itself is influenced by the breakage of the control unit
121
and enters an abnormal state (S
63
).
In this case, while the power converter
20
has been in the abnormal state, even if the selector switch
21
changes a contact from the control circuit A
121
to the control circuit B
122
to try to continue the control of the power converter (S
64
), the control circuit B
122
also detects a failure of the power converter
20
(S
65
) since the power converter
20
is still in an abnormal state, and thus the power converter has to be stopped (S
66
) and here it becomes impossible to keep controlling of the power converter
20
. Therefore, there is an issue concerning the reliability for a motion of the power control device
100
. That is, though it may be equipped with multiplex control units, a breakdown of single a control circuit may make it impossible to continue controlling the power converter
20
and there is a possibility that the power conversion device
100
will stop operating.
SUMMARY OF THE INVENTION
In view of the foregoing, it is a main object of this invention is provide a power conversion device for addressing this issue with high reliability, equipped with multiplex control units for enabling continued operating and controlling of the power converter even if the single control unit breaks while preventing the power converter from being influenced by the breakdown.
Other and further objects of this invention will become apparent upon an understanding of the illustrative embodiments to be described herein or will be indicated in the appended claims while various advantages not referred to herein will be appeared to one skilled in the art upon employment of the invention in practice.
According to an aspect of the present invention, there is provided a power conversion device including, a power converter which controls a motor in variable speed control, a first control circuit which outputs a first control signal to control the power converter, a second control circuit which outputs a second control signal to control the power converter, a first detector which detects a state of the power converter and outputs a first detection signal to the first control circuit, a second detector which detects a state of the power converter and outputs a second detection signal to the second control circuit, a switch which receives the first control signal and the second control signal and outputs one of the first control signal and the second control signal to the power converter, a selection circuit which outputs a changeover selection signal to the switch for outputting the second control signal instead of the first control signal when the switch has outputted the first control signal and the first control circuit fails.
According to another aspect of the present invention, there is provided a power conversion device including, a power converter which controls a motor in variable speed control, a first control circuit which outputs a first control signal to control the power converter, a second control circuit which outputs a second control signal to control the power converter, a restore circuit which outputs a restoring signal to restore the power converter to return a previous state of the power converter, a first detector which detects a state of the power converter and outputs a first detection signal to the first control circuit, a second detector which detects a state of the power converter and outputs a second detection signal to the second control circuit, a switch which receives the first control signal, the second control signal and the restoring signal and outputs one of the first control signal, the second control signal and the restoring signal to the power converter, and a selection circuit which outputs a chan
Tanaka Atsushi
Yoshida Hiroshi
Foley & Lardner LLP
Patel Rajnikant B.
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