Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2002-09-10
2004-04-27
Riley, Shawn (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C363S131000
Reexamination Certificate
active
06728116
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a magnetic circuit of a core-type electromagnet, inclusive of electric motors, having coils wound around ferromagnetic substances or of a coreless electromagnet having only coils wound, and more particularly to an electric circuit and a magnetic circuit constructed with two or more electromagnet coils wherein one coil is wound clockwise (S direction) and the other coil is wound counterclockwise (Z direction) and for providing a one-direction direct-current series control method of using a phenomenon that magnetic polarities are changed according to winding directions as electric currents flow with controls of a semiconductor switching device or a superconductive switching device mounted in front of the coils wound in the respective directions and a method of inducing alternating magnetic flux.
BACKGROUND ART
An alternating magnetic flux induction method which has been used so far is a method of generating an alternating electromotive force in a sinusoidal waveform due to changes of flux linkage of an induced magnetic flux in an armature coil wherein the magnetic flux of a field system is alternately induced in the armature by rotating the field system mounted on a shaft due to mechanical power and the mechanical power is obtained by attractive and repulsive forces generated through alternate applications of voltages to both ends of coils wound in an electric motor or other magnetic circuit.
The voltage or the voltage-applying method obtained as above is referred to as alternate current (AC). A concrete description added to the above will be as follows by using a view of
FIG. 1
for showing a circuit of a conventional transformer.
An alternating switching method is repeated wherein, in coils
2
and
3
wound around a core
1
of a ferromagnetic substance, a direct current (DC) voltage is applied to an input terminal
4
for a certain period of time in an “A” direction and then cut off, and just after the cutoff, the DC voltage is applied to an opposite input terminal
5
in a “B” direction. Therefore, an alternating electromotive force is generated from output terminals
6
and
7
.
The voltage applications through the alternating switching method require a high voltage application to obtain a rotation force of a high torque since reactance, that is, a functional resistance (alternate current resistance), is generated due to collisions with currents flowing against a current flow direction in addition to a coil material resistance to interrupt electric current applications in a proportion of a frequency magnitude.
In a theoretical description, the impedance is divided into a material resistance R and a reactance X largely changing according to frequencies, and the reactance is divided into the inductive reactance and the capacitive reactance. Impedance Z may be expressed as a following formula when a material resistance R, inductance L, capacitance C are connected in series:
Z
=
R
+
jX
=
R
+
j
(
X
L
-
X
C
)
=
R
+
j
(
wL
-
1
wC
)
,
and
&LeftBracketingBar;
Z
&RightBracketingBar;
=
R
2
+
X
2
=
R
2
+
(
wL
-
1
wC
)
2
[
ohm
]
In the above formula, if alternating magnetic flux may be induced without frequency changes, the reactance term jX is cancelled out, so there exists only the material resistance R.
However, a push-pull inverter showing in
FIG. 2
as a conventional voltage-applying method can obtain an alternating electromagnetic force from the output terminal
3
by applying a DC voltage, but has difficulties in real-time switching controls of both terminals since currents flow into a coil connected to a left-side switch and a coil connected to a right-side switch by switches about a common ground coil to generate the alternating electromagnetic force, deteriorates energy efficiency since currents are cut off due to current collisions when both switches all turn on as well as a phase difference of voltage and current is generated due to a dead time, and generates a reactance of interrupting current flows due to a current flow inertia when the both switches mounted on both sides are abruptly turned on and off to obtain an alternating electromotive force.
A description is made in detail as follows through a view shown in FIG.
2
.
As shown in
FIG. 2
a
, if an S
1
switch
24
turns on in the state that an S
2
switch
25
turns off, a circuit is formed in which the positive voltage of a voltage source
23
is applied in a “C” direction from a common ground
26
to part of a coil
21
connected to the S
1
switch, and to the negative voltage of the voltage source
23
along the S
1
switch
24
.
At this time, a current waveform
27
shown in
FIG. 2
b
appears across an output coil
3
, and, in reverse, if the S
1
switch
24
turns off and the S
2
switch
25
turns on, a circuit is formed in which the positive voltage of the DC voltage source
23
is applied from the common ground
26
to the part of the coil
22
connected to the S
2
switch, and to the negative voltage of the voltage source
23
along the S
2
switch
25
, so a current waveform shown in
FIG. 2
b
appears across the output coil
3
.
When the above is repeated, an alternating electromotive force is generated across the output coil
3
by a mutual induction. When a description is made with a digital logic formula, the push-pull inverter may be interpreted as a combinational logic-type switch circuit of the Exclusive-OR(XOR) type.
However, such switching power input method, in case that it is applied to an electromagnet or a transformer using an iron core, a mutual induction appears to be distorted due to an instant saturation of a magnetic substance as well as electric currents are not conducted owing to current collision when all the switches turn on due to imbalance appearing between peak values of two switching currents caused by a switching time difference of the switches
24
and
25
, and energy consumption increases due to a leakage inductance of a magnetic substance caused by the mutual induction and a hysteresis loss appearing upon interchanging N and S poles.
Particularly, since the method can be realized only a control method of a parallel structure, much more currents are required than a control method of a series structure upon applying currents at respective phases, an amount of electric power consumption increases a lot as an amount of heat release increases in proportion to the current amounts, and the heat becomes a cause of function deterioration.
Further, a method of driving an inverter of a two-phase hybrid electric motor of a two-power source type as shown in
FIG. 3
has an object of rapidly increasing currents by applying a voltage over a rating voltage to the electric motor the instant inputs to the armature change due to the switch-on and switch-off of a switching transistor for rapid clockwise (CW) and counterclockwise (CCW) conversions.
That is, in a state that a voltage of 24 V is applied from a power source
31
, it is structured that clockwise (CW) rotations are caused by turning on a transistor (TR
1
)
33
-
1
(when a transistor (TR
2
)
33
-
2
is turned off) with a transistor (TR
3
)
35
-
1
and a transistor (TR
4
)
35
-
2
alternately switching, and, in reverse, counterclockwise (CCW) rotations are caused by turning off the transistor (TR
1
)
33
-
1
in case that a transistor (TR
5
)
35
-
3
and a transistor (TR
6
)
35
-
4
are alternately switching.
The characteristics of this circuit increase response capability by rapidly increasing currents with support of 6.3 V of a power source
32
upon clockwise and counterclockwise conversions.
However, the driving circuit has a problem in that a high voltage is applied again as to a phase having been already operating with a low voltage, and can not maximize current efficiency since the circuit operates in a driving control method between phases based on a parallel-structured voltage input type.
In the meantime,
FIG. 4
a
and
FIG. 4
b
are views for showing an inverter circuit of a three-phase 180-degree conducting type electric motor and for explaining a meth
Enertec Korea Co., Ltd.
Riley Shawn
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