Electricity: electrical systems and devices – Control circuits for electromagnetic devices – Including compensation for thermal change of electromagnetic...
Reexamination Certificate
2001-09-25
2003-06-03
Huynh, Kim (Department: 2182)
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
Including compensation for thermal change of electromagnetic...
C361S161000, C361S106000
Reexamination Certificate
active
06574084
ABSTRACT:
TECHNICAL FIELD
This invention relates to an electromagnetic repulsion drive switching device for closing/opening a pair of contacts by a drive force utilizing an electromagnetic repulsion.
BACKGROUND ART
FIG. 22
is a construction diagram of an electromagnetic repulsion drive switching device of the prior art, and
FIG. 23
is a drive circuit diagram of FIG.
22
.
FIG. 22
shows the state in which a stationary contact
1
a
and a movable contact
1
b
of a vacuum valve
1
are opened (or parted) so that individual terminals
2
a
and
2
b
are “open”. A capacitor
3
is charged to a predetermined voltage from a charging power source
4
through a charge resistor
5
. When a contact-closing thyristor switch
7
a
is turned “ON” with a contact-closing gate signal from a gate pulse unit
6
, a pulsating drive current flows from the capacitor
3
to a contact-closing coil
8
a
so that a magnetic field is generated. As a result, an induction current is so generated in a repulsion member
9
that a magnetic field reversed from the magnetic field of the coil
8
a
is generated. By the interactions between the magnetic field generated by the contact-closing coil
8
a
and the magnetic field generated by the repulsion member
9
, this repulsion member
9
receives an electromagnetic repulsion from the coil
8
a
. The movable contact
1
b
, as integrated with the repulsion member
9
by the electromagnetic repulsion force, moves upward in
FIG. 22
to close (or contact)the individual contacts
1
a
and
1
b.
Since the electromagnetic repulsion drive switching device of the prior art has the construction thus far described, the several characteristics of an electrolytic capacitor to be used as the capacitor
3
generally vary with the working temperature. As a result, the drive current flow through the individual coils
8
a
and
8
b
fluctuates and raises a problem that the electromagnetic repulsion force is unstable.
Here: numeral
10
designates a reflux diode; numeral
11
a discharge resistor; and numeral
12
a voltage detector.
FIG.
24
(
a
) is a temperature characteristic diagram of the electrostatic capacitance of the capacitor
3
; FIG.
24
(
b
) is a temperature characteristic diagram of an equivalent series resistor of the capacitor
3
; FIG.
24
(
c
) is a temperature characteristic diagram of the drive current peak value of the individual coils
8
a
and
8
b
; and FIG.
24
(
d
) is an explanatory diagram illustrating waveforms of the drive currents of the individual coils
8
a
and
8
b.
FIG.
24
(
a
) is a temperature characteristic diagram of the electrostatic capacity of the capacitor
3
; FIG.
24
(
b
) is a temperature characteristic diagram of an equivalent series resistor of the capacitor
3
; FIG.
24
(
c
) is a temperature characteristic diagram of the drive current peak value of the individual coils
8
a
and
8
b
; and FIG.
24
(
d
) is an explanatory diagram illustrating waveforms of the drive currents of the individual coils
8
a
and
8
b.
In FIG.
24
(
a
), the electrostatic capacitance of the capacitor
3
is decreased by 20% at the working temperature of −20° C., as compared with that at +20° C. In FIG.
24
(
b
), the equivalent series resistor of the capacitor
3
is increased at −20° C. to about three times as high as that at +20° C. If the range of the drive current peak value, within which the precise actions are made within the working temperature range from −20° C. to +40° C., is the “working range” of FIG.
24
(
c
), a decrease of about 20% occurs at −20° C. from that at +20° C. The waveforms are illustrated in FIG.
24
(
d
).
In FIG.
24
(
d
), numeral
13
a
designates the drive current of the capacitor
3
at +20°
0
C., and numeral
13
b
designates the drive current of the capacitor
3
at −20° C. Thus, a reliably workable drive current peak value cannot be obtained on the low temperature side. If the working temperature of the capacitor
3
rises, on the other hand, the drive current increases to raise the electromagnetic repulsion force. There arises another problem that the mechanical load is augmented.
This invention has been conceived to solve the aforementioned problems and has an object to provide an electromagnetic repulsion drive switching device which is enabled to open/close the contacts precisely by confining the drive current for a contact-closing coil and a contact-opening coil within a predetermined range even if the working temperature of a capacitor changes.
DISCLOSURE OF THE INVENTION
According to this invention, there is provided an electromagnetic repulsion drive switching device in which a contact-closing coil and a contact-opening coil are arranged to confront a repulsive member having a conductivity, and in which a drive current is fed to a selected one of the individual coils from a capacitor charged to a predetermined charge voltage by a charging power source, so that a stationary contact and a movable contact are brought into and out of contact by a repulsion force of the electromagnetic force generated between the coil and the repulsion member. The electromagnetic repulsion drive switching device comprises voltage control means for controlling the output voltage of the charging power source so that the peak value of the drive current may fall within a predetermined range with respect to a temperature change of the capacitor. By controlling the fluctuations of the electrostatic capacity with respect to the temperature change of the capacitor with the output voltage of the charging power source, the peak value of the drive current is enabled to fall within the predetermined range to stabilize the switching actions.
In this invention, on the other hand, the voltage control means controls the output voltage of the charging power source such that when the working temperature of the capacitor is a first temperature for the reference, the charge voltage is set to Vc, and the drive current is set to I, and such that when the working temperature of the capacitor is a second temperature and the drive current is &agr;·I, the charge voltage of the capacitor is set to Vc/&agr;. As a result, the switching actions can be stabilized by confining the drive current within the allowable working range.
In this invention, on the other hand, the voltage control means controls the charge voltage of the capacitor as a product of the reference voltage and a resistance ratio, so that the resistance of a resistor having a temperature dependency is confined in a formula for calculating the resistance ratio. As a result, the switching actions can be stabilized by confining the drive current within the allowable working range.
In this invention, on the other hand, the resistor having the temperature dependency has a resistance having negative characteristics with respect to the temperature, and a voltage suppression element for suppressing the voltage is connected in parallel with the resistor. Even if the capacitor becomes lower than the limit working minimum temperature, the voltage suppression element can act to control the impedance at the two ends of the resistor so that the charge voltage of the capacitor can be set to the allowable maximum impressed voltage or lower.
In this invention, on the other hand, the repulsion member is made of a flat metal member and there enables a simple structure.
In this invention, on the other hand, the repulsion member is a repulsion coil for generating an electromagnetic force in the direction opposed to that of an electromagnetic force which is generated by a selected one of a contact-closing coil and a contact-opening coil. As a result, the electromagnetic force can be easily adjusted.
In this invention, on the other hand, the temperature of the capacitor is controlled to fall within a predetermined range by temperature control means so that the peak value of the drive current of the capacitor may fall within the allowable working range. With this construction, too, the switching actions can be stabilized.
In this invention, on the other hand, t
Kagawa Kazuhiko
Kishida Yukimori
Moritoh Eiji
Nakashima Tokio
Nishioka Takafumi
Huynh Kim
Leydig , Voit & Mayer, Ltd.
Mitsubishi Denki & Kabushiki Kaisha
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