Electric power conversion systems – Current conversion – Having plural converters for single conversion
Reexamination Certificate
2000-11-09
2001-10-02
Wong, Peter S. (Department: 2834)
Electric power conversion systems
Current conversion
Having plural converters for single conversion
C363S069000
Reexamination Certificate
active
06297978
ABSTRACT:
BACKGROUND
Propulsion systems for traction vehicles such as locomotives commonly use a diesel engine prime mover to drive electric generating means for supplying energy to a plurality of direct current (DC) traction motors. The generating means typically comprises a 3-phase dual output alternator where each output comprises three phase windings interconnected in a 3-phase star configuration. The alternator voltages are rectified and applied to relatively positive and negative DC buses between which the respective pairs of motors which are generally connected in parallel.
Referring now to
FIG. 1
, which depicts a typical series-parallel alternator-rectifier system
10
comprising a dual winding AC power supply (e.g. alternator)
200
interconnected with a rectifier assembly
14
including series-parallel switches
46
and
48
. The three different phases of the first set of windings
210
are respectively identified as
222
,
224
, and
226
, which may typically represent what is commonly termed as phases A, B, and C respectively. Likewise, the three different phases of the second set of windings
220
are identified as
212
,
214
, and
216
, which again, may typically represent what is commonly termed as phases A prime, B prime, and C prime respectively for the second set of windings
220
.
The rectifier assembly
14
is formed by an array of rectifiers or rectifiers, which are interconnected and arranged between the dual winding AC power supply
200
and the positive DC bus
100
p
and negative DC bus
100
n
. In
FIG. 1
, the rectifier assembly
14
has two series-parallel switches
46
and
48
and three primary legs connected in parallel circuit relationship between the DC buses. Each leg of the three primary legs comprises a four rectifiers (e.g. diodes) connected in series with one another and oriented to conduct current in a direction from negative DC bus
100
n
to positive DC bus
100
p
. A first primary leg
120
comprises a first rectifier
22
, a second rectifier
24
, a third rectifier
52
, and a fourth rectifier
54
connected in series with one another and oriented to conduct current in a direction from negative DC bus
100
n
to positive DC bus
100
p
. The second primary leg
130
comprises a first rectifier
30
, a second rectifier
32
, a third rectifier
60
, and a fourth rectifier
62
similarly connected and oriented. Finally, the third primary leg
140
also comprises a first rectifier
38
, a second rectifier
40
, a third rectifier
68
, and a fourth rectifier
70
in the same connection and orientation.
The first set of windings
210
of the AC power supply
200
is connected to the respective primary legs of the rectifier assembly
14
by three lines
102
,
104
, and
106
. Where line
102
connects at the junction of rectifiers
22
and
24
of the first primary leg, line
104
connects at the junction of rectifiers
30
and
32
of the second primary leg, and line
106
connects at the junction of rectifiers
38
and
40
of the third primary leg. Similarly, the second set of windings
220
of the dual winding AC power supply
200
is correspondingly connected to the respective primary legs of the rectifier assembly
14
by three lines
112
,
114
, and
116
. Where line
112
connects at the junction of rectifiers
52
and
54
of the first primary leg, line
114
connects at the junction of rectifiers
60
and
62
of the second primary leg, and line
116
connects at the junction of rectifiers
68
and
70
of the third primary leg. Thus, the two sets of windings
210
and
220
are effectively connected in parallel between the DC buses
100
n
and
100
p
with the series-parallel switches
46
and
48
open.
Since each of these two paths includes passing through the same number of rectifiers and since the voltage of phase
212
has the same instantaneous magnitude and polarity as the voltage of phase
222
, the parallel paths share current substantially equally. It is noteworthy the current passes through at least four rectifiers to complete the circuit. Note also, that each of the outboard rectifiers
22
,
30
,
38
,
54
,
62
, and
70
now have to conduct twice as much current as each of the inboard rectifiers
24
,
32
,
40
,
52
,
60
, and
68
. Therefore, the current rating of these rectifiers is commonly based on the higher duty of the outboard rectifiers, or the rectifier assembly
14
should be physically arranged so that the outboard rectifiers receive preferential cooling.
In addition, the described arrangement of the rectifier assemblies may be supplemented by adding rectifiers or rectifier legs to the rectifier assembly
14
. Each supplemental leg similarly connected and conducting current in a similar fashion as described above. For example, a supplemental leg in parallel to each of the legs described above. Such a configuration is depicted in
FIG. 1
with first, second and third supplemental legs
122
,
132
, and
142
respectively. Those skilled in the art will appreciate that such a parallel configuration as described provides effectively double the current rectification capability for the overall system thereby allowing for the use of reduced rating components (e.g., lower current rating rectifiers) or for higher current capability negative DC bus
100
n
and
100
p.
The above described configuration results in the certain rectifiers of each leg being required to conduct more current than others in the leg. Further, in a typical configuration the individual rectifiers may very well be part of a larger package including several individual rectifiers and further may even include interconnections between the individual elements within the package. In consideration of such a typical application, some rectifiers is such a package may be required to conduct more current than others, while others may see varying voltage constraints. This type of configuration forces under-utilization of some components to satisfy the rating requirements of others. It is therefore seen to be desirable to have a rectifier assembly, configured to reduce or eliminate under-utilized components, thereby providing maximal capability within a particular rectifier's ratings.
SUMMARY OF THE INVENTION
An exemplary embodiment is disclosed for a series-parallel rectifier system and methodology, employing multiple parallel rectification paths. The system includes a dual winding AC power supply with phase matched alternating voltages and a rectifier apparatus coupled to the AC power supply. The rectifier apparatus comprises a series-parallel switches and rectifier legs interconnected in a parallel circuit relationship, with each leg comprising several rectifiers connected in series and oriented to conduct current from a negative DC bus to a positive DC bus. Bypass legs comprising two rectifiers connected in series and oriented so as to conduct current from said negative DC bus to said positive DC bus are added in place of redundant rectifier legs and interconnected with the AC power supply.
An alternative embodiment is disclosed for a series-parallel rectifier system and methodology, employing multiple parallel rectification paths. The system includes a dual winding AC power supply with phase matched alternating voltages and a rectifier apparatus coupled to the AC power supply. The rectifier apparatus comprises series-parallel switches and rectifier legs interconnected in a parallel circuit relationship, with each leg comprising several rectifiers connected in series and oriented to conduct current from a negative DC bus to a positive DC bus. The rectifier legs are interconnected with the AC power supply.
REFERENCES:
patent: 3932765 (1976-01-01), Townshend
patent: 4009431 (1977-02-01), Johnson
patent: 4138706 (1979-02-01), Johnson et al.
patent: 4328427 (1982-05-01), Bond
patent: 4339704 (1982-07-01), McSparran et al.
patent: 4866591 (1989-09-01), Cook et al.
patent: 5894414 (1999-04-01), Jiang
Cronmiller Robert E.
Kumar Ajith Kuttannair
Cantor & Colburn LLP
General Electric Company
Vu Bao Q.
Wong Peter S.
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