CA2086185C - Dual stator winding connection - Google Patents

Abstract

There is disclosed a dynamoelectric machine having a dual stator winding comprising a pair of windings each connected in a three phase star configuration from a respective neutral. The three phases of each of the pair of windings are normally displaced from each other by 30 electrical degrees. The improvement includes first and second terminals at the midpoint of each of the three phases of each of the pair of windings which terminals are normally connected to each other. This allows the dynamoelectric machine to be connected to a twelve pulse LCI source.
Alternatively, the first terminal of each three phase windings may be connected to the second terminal of its corresponding phase winding to provide cross connected windings having zero electrical degrees displacement. The line terminals of the corresponding cross connected windings may be connected to a conventional power source.

Description

~o~sm5 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 .. ,: w 208fi~.85 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.

208fi1~5 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.

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.

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.

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 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.

Claims (5)

1. 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 voltages of corresponding phase windings of each of the pair of windings are normally displaced from each other by 30 electrical degrees, 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 being 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.

2. A dynamoelectric machine having a stator winding comprising:
a first winding having three phase windings connected in a star configuration from a first neutral point, each of the three phase windings including first and second terminals at its midpoint;
a second winding having three phase windings connected in a star configuration from a second neutral point, each of the three phase windings including first and second terminals at its midpoint;
the first and second terminals of each phase winding of each pair of windings normally being connected to each other to provide a dual stator winding with the first and second windings having corresponding phase voltages normally displaced thirty electrical from one another; and, the first and second neutrals being adapted to be connected to each other, the first terminal of each phase winding of the first winding being adapted to be connected to the second terminal of the corresponding phase winding of the second winding, and the first terminal of each phase winding of the second winding being adapted to be connected to the second terminal of the corresponding phase winding of the first winding to provide cross connected corresponding windings so that the voltage between each phase cross connected corresponding winding has zero electrical degrees of displacement.

3. The dynamoelectric machine of claim 2 wherein line terminals for the corresponding cross connected windings are adapted to be connected to the same source.

4. The dynamoelectric machine of claim 1 wherein the first and second neutrals are grounded when connected in the normal winding configuration.

5. The dynamoelectric machine of claim 2 wherein the first and second neutrals are grounded when connected in the normal winding configuration.