Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DUAL STATOR WINDING CONNECTION
FIELD OF THE INVENTION
The present invention relates to a dual stator winding for a
dynamoelectric machine wherein a pair of windings are phase
displaced thirty electrical degrees from each other and are adapted
to be connected in one of two winding configurations to allow the
dynamoelectric machine to operate with a twelve pulse power
source or alternatively a conventional power source.
BAC&CGROUND OF THE INVENTION
It is common to find dynamoelectric machines of both single
and dual three pha;>e stator winding configurations operating at the
same industrial site. For example, an ore grinding mill usually has
two dual stator winding motors which drive the mill at variable
speed through pinions where the motors are supplied by a twelve
pulse source. At the same installation other mills running at
constant speed may require a single stator winding motor
connected to a conventional power source and having the same or
close to same rating as the dual stator winding motors.
Accordingly) motors of similar design but of different winding
configurations are manufactured to meet the requirements of the
mill site. If standardization of winding configuration could be
achieved, then reduced manufacturing costs and an improved
motor application flexibility may be realized.
Standardizing the winding configuration of stators to operate
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from conventional and non-conventional supplies has not been
feasible because of the requirement that dual stator windings
operate with a twelve pulse load commutated inverter (LCI) source.
The twelve pulse source voltage is commonly obtained from two six
pulse LCI supplies operating in parallel and displaced thirty
electrical degrees in phase from each other. The thirty electrical
degrees phase shift in the twelve pulse LCI source is obtained by
using two transformers, one for each six pulse LCI source. One
transformer is connected in a delta-delta configuration to one of the
six pulse LCI supplies while the other transformer is connected in a
delta-wye configuration to the other six pulse LCI source so that the
output voltages of the transformers and six pulse LCI supplies are
displaced thirty electrical degrees.
The design of the stator windings of the motor to operate in
conjunction with the two six pulse LCI supplies has resulted in the
motor having two windings wound about the stator with the
respective phases of each of the two windings being thirty electrical
degrees displaced from each other. Consequently) it is not
possible to connect the dual displaced stator windings to a
conventional power source because the windings are displaced in
phase from each other so as to operate with a twelve pulse LCI
source. Typical six and/or twelve pulse LCI supplies operating in
conjunction with single and dual displaced stator windings of
motors are described in U.S. Patent Nos. 4,654,572 issued March
31, 1987 to Hirata, 4,814,964 issued March 21, 1989 to Schauder
et al, 4,873,478 issued October 10) 1989 to Weiss) and 4,426,611
issued January 17) 1984 to Espelage et al.
SUMMARY OF THE INVENTION
It is therefor an object of the present invention to provide a
dynamoelectric machine having a dual stator winding that may be
adapted either at the manufacturing site or in the field to operate in
conjunction with a twelve pulse power source or alternatively with a
conventional power source.
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In accordance with an aspect of the present invention there is
provided in a dynamoelectric machine having a dual stator winding
comprising a pair of windings each having three phase windings
connected in a star configuration from a respective neutral such
that the voltages of corresponding phase windings of each of the
pair of windings are normally displaced from each other by 30
electrical degrees. The improvement is characterized in that of
each of the three phase windings of each pair of windings includes
a first and a second terminal at its midpoint which terminals are
normally connected to each other. The first terminal of each of the
three phase windings of the pair of windings is adapted to be
connected to the second terminal of its corresponding phase
winding and the nuetrals of the pair of windings being adapted to be
connected to each other so that the voltage between each winding
has zero electrical degrees of displacement. By connecting the
terminals in this latter arrangement it is possible to connect the
dynamoelectric machine to a conventional three phase power
source or to a six pulse LCI.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the nature and objects of the
present invention reference may be had to the accompanying
diagrammatic drawings in which: ,
Figure 1 is a schematic representation of the dual winding
synchronous motor of the present invention connected in a
conventional manner to a twelve pulse LCI power source;
Figure 2 is a schematic representation of the dual winding
synchronous motor of the present invention connected to a non-
conventional manner to a conventional power source; and,
Figures 3A and 3B are electrical phasor diagrams illustrating
the displacement in phase angles between the winding
configurations of Figures 1 and 2 respectively.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to Figure 1 there is shown a dual stator winding 10
for a dynamoelectric machine. The dual stator winding is illustrated
in a conventional connection arrangement to a twelve pulse load
commutated inverter (LCI) power source 12.
The dual stator winding 10 comprises a first winding 14
having three phase windings 14a, 14b and 14c connected in a star
configuration from a first neutral 16. Nuetral 16 is shown grounded
through a resistance. Each of the three phase windings 14a, 14b
and 14c includes at its respective midpoint first and second
terminals 18 and 20, respectively. In this connection arrangement
the terminal 18 is connected to terminal 20 of each phase winding.
The ends of each phase winding 14a, 14b and 14c remote from
neutral 16 are respectively connected to source lines a1, b1, and c1
of channel 22 of power source 12.
The dual stator winding further includes a second winding 24
having three phase windings 24a, 24b and 24c connected in a star
configuration from a second neutral 26. Nuetral 26 is shown
grounded through a resistance. Each of the three phase windings
24a, 24b and 24c includes at its respective midpoint first and
second terminals 28 and 30, respectively. In this connection
arrangement the terminal 28 is connected to terminal 30 of each
phase winding. The ends of each phase winding 24a, 24b and 24c
remote from neutral 26 are respectively connected to source lines
a2) b2, and c2 of channel 32 of power source 12.
With the dual stator windings connected as described above,
corresponding phases 14a and 24a, 14b and 24b, and 14c and 24c
of windings 14 and 24 are displaced 30 electrical degrees. This
permits the line terminal ends of the phase windings of the
windings 14 and 24 to be connected to respective six pulse power
supplies 22 and 32 of 12 pulse LCI source 12.
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Figure 1 illustrates the application of the present invention in
what is commonly referred to as a twelve pulse load commutated
inverter drive system of the basic type described in aforementioned
U.S. Pat. No. 4,426,611. !n the twelve pulse system, the motor
stator has two sets of windings 14 and 24 whose voltages are
phase displaced with respect to each other by 30 electrical
degrees. Two LCI channels 22 and 32 supply the two sets of
windings 14 and 24. Channel 22 includes a source side converter
34, a load side inverter 36 and a link circuit 38. Three legs a1) b1,
and c1 of the load side converter 22 are connected respectively to
phase windings 14a, 14b, and 14c of winding 14. In a similar
manner) channel 32 includes a source side converter 44) a load
side inverter 46 and a link circuit 48. Three legs a2, b2, and c2 of
the load side converter 48 are connected respectively to phase
windings 24a, 24b, and 24c of winding 24.
The two load commutated inverter circuits, or two channels
22 and 32, are suppiied by a transformer arrangement indicated
generally at 150 which includes a delta connected primary 152
connected to a power source LI, L2, L3. A first secondary winding
154 of the transformer 152 is in a wye configuration and supplies
the source converter 34 of channel 22. In a similar manner a delta
connected secondary 156 supplies the source side converter 44 of
channel 32. Operation of the power circuit illustrated in Figure 1 is
such that the respective channels 22 and 32 produce sine waves
which are 30 electrical degrees phase displaced.
Referring to Figure 2, there is shown a schematic
representation of the dual winding synchronous motor of the
present invention connected to a conventional three phase
alternating power source 50. It should be understood that the
winding circuit of the stator winding shown in Figures 1 and 2 would
be the same, however) the only difference would be the
connections of the line terminals for each phase, the nuetrai
connections and connections of the midpoint terminals.
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Accordingly, the stator winding of Figure 2 has the same numeral
designations as the winding of Figure 1.
In Figure 2, the first nuetral 16 of winding 14 is connected to
the second neutral 26 of winding 24. The first terminal 18 of each
of phase windings 14a) 14b, and 14c is connected to the second
terminal 30 of the corresponding phase winding 24a, 24b, and 24c
of winding 24. Similarly, the first terminal 28 of each of phase
windings 24a, 24b, and 24c is connected to the second terminal 20
of the corresponding phase winding 14a, 14b, and 14c of winding
14. Also) the line terminal ends of corresponding phases 14a and
24a, 14b and 24b and 14c and 24c are connected together and
meet respectively at source lines a3, b3, and c3. This connection
arrangement of the dual windings 14 and 24 provides for a cross
connected corresponding windings that result in the voltage in each
adjacent cross connected corresponding winding having zero
electrical degrees displacement. A more detailed description of the
electrical displacement of the voltages in windings 14 and 24 of
Figures 1 and 2 is provided hereinafter with reference to Figure 3.
Referring to Figures 3A and 3B the phasor diagrams are
illustrated showing the resultant phase displacements of the
winding configurations of Figures 1 and 2) respectively. For
simplification, the phasors have been identified by the same
designation as the phase winding the phasor represents. In Figure
3A the voltage phasors are shown for each phase of each winding
as phasors 14a and 24a, 14b and 24b) and 14c and 24c. Each
voltage phasor 14a, 14b, and 14c is displaced from each
corresponding voltage phasor 24a, 24b, and 24c by 30 electrical
degrees. With respect to each of the phasors 14a, 14b and 14c of
winding 14, these phasors are displaced 120 electrical degrees
from each other. The relative displacement of the phasors 24a,
24b, and 24c of winding 24 are also displaced from each other by
120 electrical degrees. Each phasor of each phase winding is
shown in Figure 3A to comprise a first and a second part
representative of the winding on either side of the mid point. Hence
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phasor 14a comprises the sum of phasors 14a(1 ) and 14a(2). The
disignations for the phasors in windings 14b, 14c, 24a, 24b, and
24c are similar to that described for winding 14a in Figure 3A.
Referring to Figure 3B, the resultant phasors represents a
sum of the voltage in each corresponding phase winding. From
Figure 2 it can be seen that corresponding phase windings 14a and
24a are cross coupled or connected at their respective midpoints.
The voltage phasor in phase winding 14a between nuetral 16 and
terminal 18 is depicted in Figure 3 as 14x(1 ). The voltage phasor
in phase winding 14a between terminal 20 and source terminal a3
is depicted as 14a(2). The phasor 24x(1 ) is for the voltage in
winding 24a between neutral 26 and terminal 28. The phasor
24a(2) represents the voltage between in phase winding 24a
between terminal 30 and source terminal a3. Because nuetrals 16
and 26 are connected to each other and phase windings 14a and
24a are connected to the same source terminal) the voltage phasor
of 14a(2) is added to the phasor 24a(1 ) and the phasor 24a(2) is
added to phasor 14a(2). The resultant voltage between each cross
connected phase winding has zero electrical degrees of
displacement. The designations for the phasors and resultant
phasors in windings b and c are similar to that described for
winding a in Figure 3B.
It should be understood that it is envisaged that the winding
terminals 18 and 20 and 28 and 30 may comprise terminals that
are accessible during assembly and are hard connected at
assembly or may comprise a double pole single throw switch for
each phase.
