US1849519A - Method of starting alternating current machinery - Google Patents

Description

March 15, 1932. F. w. GAY I 7 1,849,519

METHOD OF STARTING ALTERNATING CURRENT MACHINERY Filed May 29, 1930 2 Sheets-Sheet l FIQ. 5

INVENTOR March 15, 1932.

F, w. GAY 1,849,519

METHOD OF STARTING ALTERNATING CURRENT MACHINERY Filed May .29, 1930 2 Sheets-Sheet 2 FIG. 6.

INVENTOR Patented Mar. 15, 1932 PATENT OFFICE FRAZER W. GAY, OF NEWARK, NEW JERSEY METHOD OF STARTING ALTERNATING- CURRENT MACHINERY Application filed May 29, 1930.

This invention relates, generally, to the starting of alternating current machines, and the invention has reference more particularly, to means for starting such motors as may conveniently be-adapted to have their stator windings divided into two parallel windings for normal operation.

\ In my U. S. patent application Ser. No.

124,191 I explain the disadvantages inherent 0 in present systems of starting alternating current machines.

The principal object of the present invention is to provide a novel means for starting alternating current motors, synchronous condensers, frequency changers, etc., said starting means being adapted to inherently provide the proper starting voltages for said machines, whereby the starting operation is performed smoothly and without the neces- 29 sity of going through a series of high speed operations.

Another object of the present invention is to provide a novel starting means of the above character which is of extremely simple construction and which employs merely the machine winding and relatively inexpensive switches for elfecting the starting of the machine.

Still another object of the present invention lies in the provision of a starting means of the above character which is easily 0perated to efiect the starting of a machine. the starting action being progressive and continuous and taking place without sudden or violent current interruptions.

A further object of the present invention is to provide a starting means ofthe above character which merely requires the closing of switches to complete the starting operation, such switches being closed without the subsequent occurrence of high voltage or cur rent surges.

Another object of the present invention is to provide a novel starting means of the above character which allows a minimum starting current to flow and accomplishes the passage from starting to running position by the simple closure of a switch; such switch being closed at a time when the voltage across Serial No. 457,073.

the opencontacts isat a minimum and relatively very low value.-

A further object of the present invention lies in the provision of a starting means employing a series and then parallel arrangement during the starting operation and in which each phase winding is continuous, having a minimum number of wires tapped thereto and brought out of the machine to effect the parallel arrangement.

In carrying out the invention in its preferred form, each phase winding of the electrical machine is wound in two winding groups, each such winding group being preferably distributed circumferentially over one half ofthe stator, although such exact distribution of the winding groups is not imperative, especially in machines having many pol-es.

Other objects and advantages will become apparent from the specification, taken in connection with the accompanying drawings wherein the invention is embodied in concrete form.

In the drawings Fig. 1 is an end elevation of a motor embodying the present invention.

Fig. 2 is a diagrammatic representation of the motor of Fig. 1.

Fig. 3 is a diagrammatic representation of the vector arrangement of windings shown in Fig. 2, with D. C. excitation applied to the field N1, N2, N3, etc. Fig. 1.

Fig. 4 shows the arrangement of windings of motor shown in Fig. 1 when switch 16 Fig. 2 is closed, that is for the running position.

Fig. 5 is a fragmentary, schematic view illustrating the operation of the machine; and Fig. 6 is a schematic conventional diagram of a developed winding for an eight pole stator having two slots per pole per phase or forty-eight'total slots with one coil per slot.

Fig. 1 shows a motor stator having uniformly distributed stator coils, one half'of said coils being connected to form three separate phase windings distributed over one half ofthe machine as MN, and the other half of said coils being connected to form three sepa- I C1 and A2 are in series across leads 3-1 and shown for poles N1, and N5 respectively.

Bower is fed to the motor through' switch 15 and leads 1, 2, and windings are connected from series to delta by connections 7, 8, 9, 10,

11, 12 and switch 16. I V

Fig. 2 shows diagrammatically the meth od of connecting and switching thewindings of the motor oi Fig.1. A phase winding in the half NM Fig. 1 is permanently connect-.

ed in series with a phase'wmdlng 1n the half OP Fig. 1 to form three series connected pairs of windings as A1 B2- C1 A2- and B1 C2 connected across powerleads 2, 3-3, 1- and 1, 2 respectively. Wires 8, 12, and 10 are brought out of the machine from the junction points of these windings A1 B2- C1 A2- and B1 C2 respectively as shown in Figs. 1 and 2. A three pole single throw switch16 has the hinge clips of its poles 4, 5, and 6 connected by wire 7 to lead 1; by wire 12 to thejunction point of windings G1 and A2 and by wire 9 to lead 3 respectively and has the jaw clips of its poles 4, 5, and 6 connected by wire 8 to the junction point of windings A1 and B2, by wire 11 to lead 2 and by wire 10 to the junctionpoint of windings B1 and C2 respectively.

Fig. 3is added to illustrate the operation of the machine as more fully explained later.

Fig. 41 shows the windings as connected after the machine has reached full speed and switch 16 has been closed. 7

A studyof Fig. 6 will show that with switch 16 open, windings A1 and B2 are connected in series across leads 2-3; windings windings B1 andC2 are in series across leads l-2all as shown in Fig. 2.

A further study of Fig. 6 will show that with switch 16 closed; windings A1 and A2 are connected in parallel across leads 2-1; windings Cl andC2 are connected in parallel across leads 3-2 and windings B1 and of Fig; 5 shows that at the instant shown the laminated magnetic pole piece N1 partially Jcloses'theimagnetic circuits interlinlcing two phase 'groups,; while the reluctance of the other phase group will bevery high since its magnetic circuit is not so closed. As pole N1 starts to rotate, the low reactance and consequent high starting current Wlll be associated with one phase after another in the direction of rotation (A, B, C as shown). These so called harmonic or unbalanced currents are also associated with all three machine phases causing in effect a circulating current around the delta and excessive machine heating during the starting period. For this reason it has not been customary to wind salient pole machines delta. 7

On the other hand, in a star wound machine as now commonly used the phase winding: having, at the moment, a low reactance 1s associated in series relation with two phases having, at that moment, a relatively high re- Theoperation of the invention is as fol-V 95.

lows.

With switch 16 open, switch 15 is closed and three phase voltage is applied to theseries connected windings as shown in Fig. 2. It is who noted that Fig. 2 is looked at from the connection end or the opposite end from Fig. 1 so that, while the rotation Fig. 1 is shown clockwise, the rotation in Fig. 2 is shown counter clockwise. The rotation of one half of the machine (alternate windings) is Al, B1,.C1, while the rotation of the other halfof the winding is A2, B2, C2 as shown. Since there is a shift in phases at the stator positions, PM and NO there will be dead points at these positions and the stator flux will revolve in both halves in the same direction and at one point jump ahead in its travel and at the other point jump back in its travel. If the machine is a synchronous motor with D. C. excited field, the field circuit is excited after the motor has reached substantially full speed. After the field circuit is closed, polarity will be impressed on all windings by the uniformly revolving D. C. excited fields rather than by the discontinuous revolving stator fields and a voltage of identical time phase will be generated in phase groups similarly located with respect to rotor field poles;- that isthe voltage generated in the A1 group on theMN'side will be identical in time phaseiwith the voltagegeneratedin the A2 group' on the OP side; The-vector relation of all the windings is shown in Fig. '3.

A study Fig. 3 will show that there will be substantially no voltage between the unction points of series connected windings and the leads to which switch 16 connects them when the machine has reached synchronous speed after starting and with the exciting field circuit energized, that is for example, there will be substantially no voltage between the junction point of say windings A1 B2 and phase lead 1 as indicated in Fig. 3. Hence there will be substantially no voltage across the open poles 4, 5 and 6 of switch 16 Fig. 2 so that when switch 16 is closed there will be no sudden disturbing rush of current.

While I have shown an eight pole synchronous machine, it is to be understood that my invention may also be used with induction motors and with machines of any number of poles.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is 1. An alternating current motor comprising six windings, three of said windings being uniformly distributed around one half of the stator in three phase relation and the remaining three of said windings being uniformly distributed around the other half of the stator in three phase relation, each of said windings in one half of the stator being connected in series with a winding of dissimilar phase position in the other half of the stator to form a three phase delta circuit for starting.

2. An alternating current motor having two equal turn windings per phase, two of said windings of dissimilar phase positions being connected in series delta during the starting period, and a three pole single throw switch arranged on closing to alter said series delta connection so as to connect like pairs of phase windings in multiple delta arrangement.

3. A motor having three sets of phasewindings uniformly distributed on one half of the stator and three similar sets of windings 011 the other half of the stator, wires permanently connecting each set of phase windings on one half of the stator in series with a set of phase-windings of diii erent phase position on the other half of the stator, thereby providing a plurality of pairs of series connected dissimilarly positioned sets of phase-windings and wires permanently connecting said series pairs in delta for the motor starting period, said series connections and said delta connections being so arranged that the phase rotation in each of said halves of the stator is the same and switch means for connecting windings of similar phase in parallel during the running period.

' 4. An alternating current motor having a plurality of windings permanently connected in series, said motor being arranged to be connected to a supply circuit so that during the starting period said windings are connected in series delta arrangement, and switching means for directly switching said windings from said series delta arrangement to parallel delta arrangement after said motor has reached synchronous speed, whereby the physical continuity of said series delta connection is undisturbed during the operation of said switching means.

5. An alternating current machine comprising, a stator having two sets of windings, each of said sets consisting of a plurality of phase-winding groups uniformly distributed over half of said stator, each phasewinding group of one stator half being permanently connected in series with a dissimilar phase-winding group of the other stator half, thereby providing pairs of dissimilarly positioned series connected phasewinding groups, said pairs of phase-winding groups being permanently connected in series delta arrangement for facilitating the starting of said machine, and switching means connected to the terminals of said phase winding groups for connecting the similarly positioned phase-winding groups on the two halves of said stator in parallel with one another and connecting said parallel groups in delta arrangement for normal operation.

6. An alternating current machine having winding groups distributed over the stator thereof, means for permanently connecting winding groups of a certain phase position on one part of said stator in series with winding groups of a differing phase position on a second part ofsaid stator to facilitate the starting of said machine, and switching means for further connecting said winding groups of said certain phase position on said first named stator part in parallel with winding groups of a similar phase position on said second named stator part during normal machine operation.

7. An alternating current machine arranged to be supplied with operating current from a three phase power circuit, said machine having two dissimilar phase windings permanently connected in series across each phase of said power circuit, thereby forming a series delta connection, and switching means connected to said windings, said switching means being arranged on closing to connect two similar phase windings in parallel across each phase of said power circuit, thereby forming a parallel delta connection in addition to said series delta connection.

8. The method of starting an alternating current motor having a plurality of windings supplied with'current from the leads, ofp a three phase supply circuit, which consists in first-f operating the motor with said windings connected in pairs, the two windings ofeach of said pairs being of dissimilar phase relation, with each consecutive pair in series across twoconsecutive leads of said supply circuit, and then further operating I the motor with the juncture point of each respective pair of windings connected to that supply circuit leadwhich is not connected to their ends. v V I FRAZER W. GAY.

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