US2735058A - Reversible commutating-pole motors - Google Patents

Description

Feb. 14, 1956 M. J. PASCULLE 2,735,058

REVERSIBLE COMMUTATING-POLE MOTORS Filed Nov. 26, 1954 Conlrollable and Controllable and Reversible Excitation Reversible Excitation Fig.4.

Controllable and Reversible Excitation Controllable and Reversible Excitation WITNESSES INVENTOR Maurice J. Pasculle BY Q73 a ATTORNEY United States Patent 2,735,058 REVERSIBLE COMMUTATING-POLE MOTORS Maurice J. Pasculle, Wilkinsburg, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 26, 1954, Serial No. 471,275 Claims. (Cl. 318-297) My invention relates to large reversible variable-speed direct-current motors in which the commutation problems are very difiicult. These difiiculties arise from the fact that such machines have individual diflerences of such magnitude as to require special shop-testing before being sold, so as to make necessary adjustments in the precise magnitude of the commutating-pole strength, at various loadings and various speeds of each individual motor.

My present invention relates to a modification in the designs shown in my Patent No. 2,666,882, granted January 19, 1954, and in my copending application, Serial No. 367,297, filed July 10, 1953, now Patent 2,693,564, granted November 2, 1954. Both of these earlier designs provided a means for making individual shop-adjustments in the field-strength of the commutating poles, and for automatically correcting this commutating-pole strength in accordance with variations in the main-fieldstrength. Neither of these earlier designs was practically applicable to reversible motors. The copending application contained a vague reference to reversible motors, in referring to reversible mills by way of example, but it showed no means for applying its invention to reversible mill-motors, other than by changing the commutation-controlling connections every time the polarity of the field-winding is reversed.

The difficulty arises from the fact that the requirements of the users of such motors, demand that the rest of the motor-connections remain untouched when the motorfield is reversed. Not only is there the problem of circuits which carry currents of substantial magnitude, and which would require sizeable circuit-breakers or contactors for their reversal, but also the timing would be a problem, because neither the field-current nor the motor-flux reverses instantly upon a reversal of the exciting-voltage which is applied to the field-winding.

According to my present invention, I provide a rectifying means which causes the corrective circuit, for correcting the commutating-pole strength in accordance with variations in the field-excittaion, to produce its commutating-pole correction in the same direction, regardless of the polarity of energization of the field-Winding of the motor.

Several illustrative forms of embodiment of my invention are shown in the accompanying drawing, wherein the four figures are simplified diagrammatic views illustrating various alternative designs.

The essential basic feature of a motor to which my invention is applicable include a rotatable motor-armature M and a stationary field-member. This field-member includes a field-winding 1, or exciting-winding-means, which is placed on the main field-poles of the machine, a series compensating winding 2, which is a distributed winding placed in the faces of the main exciting-poles, and a series commutating winding 3, which is carried by the commutating poles or interpoles of the machine. The main motor-circuit is energized from a direct-current source of supply, which is represented by the terminals (-1-) and The compensating and commutating 2,735,055 Patented Feb. 14, 1956 windings 2 and 3 are electrically connected in series with each other and in series with the armature M. Usually, these windings 2 and 3 are connected together, and are considered together as a circuit-unit of the motor, so far as external circuit-connections are concerned. In the illustrated examples, the positive power supply-terminal (-1-) is connected to one terminal of the armature M, which thus becomes the positive armature-terminal. The negative armature-terminal 4 is connected to the compensating winding 2, which is connected in series with the commutating winding 3, which is connected to the negative supply-terminal The field-winding 1 is energized by any suitable excitation-power-means which applies a reversible and vari able direct-current excitation-controlling-power to said winding. In the illustrated examples of my invention, the excitation-power-means is shown in the form of a directcurrent exciter-machine E, which has a controllable and reversible excitation, as indicated by legend. It will be understood that a reversal of the excitation of the motor M causes a reversal of the direction of rotation of the motor, since the armature-connections remain unchanged.

My invention makes use of some one of the known old means, or any equivalent new means, for causing the commutating poles, or the commutating-winding-means, to be excited with a current or power which is mainly proportional to the armature-current and to a smaller extent proportional to the magnitude of the main-field excitation. My invention adds, to such a means, a means for making the excitation-responsive control of the commutating-pole flux independent of the direction of the exciting-current or voltage, so that the excitation-responsive communtating-pole control operates in the same direction for both directions of rotation of the main motor M.

Thus, in Figs. 1 and 2, I have adapted my present invention to the form of commutating-pole control which uses an auxiliary commutating-pole winding, as shown at 5 in Fig. l, and at 6 in Fig. 2. The general principles of this auxiliary commutating winding are described and claimed in my previously mentioned Patent 2,666,882. This auxiliary commutating winding 5 or 6, as the case may be, is placed on the commutating pole in addition to the main commutating winding 3; and the auxiliary commutating winding 5 or 6 must always be energized in such direction as to make it act cumulatively with respect to the main commutating winding 3, as indicated by the arrows in Figs. 1 and 2.

In Fig. 1, the auxiliary commutating winding 5 is provided with a midtap 7, which in effect divides the winding into two equal parts. The midtapped winding 5 is provided with two terminals 51 and 52, which are both connected to one of the exciter-terminals E1 through one or the other of two oppositely directed rectifiers 11 and 12, respectively. The main field-winding 1 of the motor is connected between the other exciter-terminal E2 and the midtap 7 of the auxiliary commutating winding 5. The respective halves of the auxiliary commutating winding 5 are shunted by means of adjustable rcsistances R1 and R2, respectively, which are factoryadjusted to take care of the exact commutation-requirements of each individual motor before it leaves the factory.

It will readily be observed, in Fig. 1, that if the exciter is of such polarity that its terminal E2 is positive, current will flow through the midtap 7 and through the left half of the auxiliary commutating winding 5, and thence through the terminal 51 and the rectifier 11 to the negative exciter-terminal E1. On the other hand, if the exciterpolarity is reversed, in order to reverse the direction of operation of the motor M, the exciter-terminal E1 will be and the terminal 52 to the right half of the auxiliary 'commutating winding 5. Thus, whichever may be the polarity of the main-field excitation, the auxiliary commutating winding 5 will add variable number of cumulative ampere-turns to augment the ampere-turns of the main commutating winding 3 in proportion to the magnitude of the main-field excitation of themotor.

in Fig. 2, an untapped auxiliary commutating winding 6 is provided, and hence this winding can have only half of the number of turns required by the tapped commutating winding 5 in Fig. 1. In Fig. 2, I use a rectifier-bridge 13 of which one diagonal is connected in series with the main-field winding 1, while the other diagonal is connected across the terminals of the auxiliary cumulative commutating winding 6. The result of this connection is that the auxiliary commutating Winding 6 is supplied with or by a direct or unidirectional field-current it, which is always in the same direction, regardless of the polarity of the exciter E.

in Fig. 3, I show my present invention applied to a form of commutating-flux control which is described and claimed in my copending application Serial No. 367,297, new Patent 2,693,564. In this form of control, no auxiliary commutating winding is required, but the main or series-connected commutating winding 3, and preferably also the serially connected compensating winding 2, are shunted by a shunting circuit consisting of two serially connected adjustable resistances R3 and R4, the resistancc-value adjustments being for the purpose of suiting the precise requirements of each individual motor, as determined by factory-tests before the shipment of the motor. Thus, one terminal of the shunt-circuit resistance R3 is connected to the terminal of the commutating winding 3, while the other terminal of said resistance R3 is connected to a common connecting-point 14 between the two resistances R3 and R4. The other terminal of the resistance Rd is connected to the previously mentioned compensating-winding terminal 4, which is between the compensating Winding 2 and the negative terminal of the motor-armature M.

in Fig. 3, an excitation-responsive control-circuit means is provided, which directly includes only one of the two shunting-circuit resistances R3 and R4, for example the resistance R3. In the form of invention which is shown in Fig. 3, this circuit is energized with a field-current I: which is in the same direction, regardless of the polarity of the exciter E, this result being brought about by the use of a rectifier-bridge 13 as described for Fig. 2. In this manner, the value of the commutating-poleexcitation is initially adjustable (at the factory) to the exact require ments of each particular motor, and after that, the commutating pole excitation is automatically varied in accordance with the motor-load or armature-current (which controls the resistance-drop between the two serially connected windings 2 and 3), and also in accordance with the motor-speed, which depends reciprocally upon the magnitude of the exciter-voltage or current (which controls the voltage-drop through the resistor R3), as explained in my aforesaid copending application. My present addition of the rectifier-bridge 13 makes it possible to obtain the same cumulative speed-responsive control, regardless of the direction of rotation of the main motor M, thus making this commutating-pole control practically applicable to reversible motors.

in all forms of embodiment of my invention, the excitaticn-responsive control of the commutating-pole strength is essentially responsive to the magnitude of the variable field-winding excitation, without being responsive to the direction or polarity of this excitation. it is obvious that this excitation-response can be obtained by using, as the control-function, either the exciting current or the exciting voltage. in the forms rat-embodiment of my invention which are shown in Figs. 1, 2, and 3, the exciting-current is used to control the commutating-pole excitation.

It is to be understood, however, that in all applications of my invention, the excitation-control might, theoretically, as well have been responsive to the excitation-voltage as to the excitation-current, although there are practical considerations in favor of the current-response.

Thus, Fig. 4 broadly illustrates the use of the excitervoltage to control or modify the commutating-pole excita tion. This simply entails the connection of the rectifierbridge 13 in shunt across the exciter-terminals E1 and E2, instead of being conected in series with the exciter-output, as in Fig. 3, for example.

In all forms of embodiment of my invention, the armature-current which flows through the main or series commutating-pole winding 3 produces the main part of the total commutating-pole excitation, this part being proportional to the armature-current. In each case, a smaller part of the total commutating-pole excitation is supplied by a smaller number of cumulative ampere-turns which are proportional to-either the field-current or the fieldvoltage of the main-field excitation, these cumulative ampere-turns being either the .excitingcurrent in the auxiliarycommutating winding 5 or 6 in Fig. l or Fig. 2, or a relatively small variable part of the current in the main commutating-pole winding 3 in Fig. 3 or Fig. 4, which varies in proportion to either the field-current or the field-voltage of the main field-winding 1 or the variable exciter E. In every case, according to my present invention, some sort of rectifying means is provided, for converting the commutation-controlling part of the reversible current or voltage of the reversible exciter E into unidirectional-current power, which furnishes the small cumulative ampere-turns of the commutating-pole excitation, so that, even when the exciter E is reversed, its efiect on the commutating-pole excitation is always cumulative with respect to the main armature-current-responsive ampere-turns of the commutating-pole excitation.

While I have illustrated my invention in several illustrative forms of embodiment, I wish it to be understood that I am not at all limited tothe precise forms whichrhave been chosen for illustration, as many changes may be made within the concept of my invention, by the substitution of equivalent parts or circuits, or by the omission of unneeded details, or the addition of other details which may he wanted.

I claim as my invention:

l. A reversible variable-speed direct-current motor, including a rotatable armature-member and a stationary field-member; said field-member having exciting-windingmeans, a series compensating winding, commutatingwinding-means, an excitation-power-means for applying a reversible and variable direct-current excitation-controlling-power to said exciting-winding-means, and a commutating-power-means for exciting said commutatingwinding-means with a power which is mainly proportional to the armature-current and to a smaller extent proportional to the magnitude but not the direction of the excitation-controlling-power; said commutating-power means including a rectifying means which converts some of said reversible excitation-controlling-power into unidirectional-current power for said commutating-powermeans.

2. A'reversible variable-speed direct-current motor, including an armature, a field-winding, a series compensating winding, a series commutating winding, an auxiliary cumulative commutating-winding-means, a means for applying a reversible and variable directcurrent excitationcontrolling-power to said field-winding, and a rectifying means for converting some of said reversible excitationcontrolling-power into unidirectional-current power and applying the same to said auxiliary commutating-windingmeans.

3. A 1 reversible variable-speed direct-current motor, including an armature, a field-winding, a series compensating winding, a seriescommutating winding, a two-part auxiliary commutating winding, a means for applying a reversible and variable direct-current excitation-controlpower into unidirectional-current power and applying the ling-power to said field-winding, and a rectifying means same to said auxiliary commutating winding. for converting some of said reversible excitation-control- A rsi le a ia l p direct-Current motor, ling-power into unidirectional-current power, aid re tifyeluding an armature, a field-winding, a series compensatlng ing means comprising two oppositely polarized rectifying- 5 Winding, a series commutating Winding, a means for apcircuits, one for each part of said auxiliary commutating p y g a v rsible and variable direct-current excitationwinding, whereby one part receives current during one Controlling power to said fieldwmdmg, a t g cucwt polarity of the excitation-controlling power, and the other Cimnecied HQYQSS least f comqlutatlflg fivlndlngg P P i s C rr nt during the opposite polarity, ea h not across said armature, said shunting circuit containing part receiving it current i a di ti hi h i cumu- 10 trvo serially connected resistance-devices, and a control l ti i h respect to the series commutating winding circuit means which directly lncludes only one of said 4. A reversible variable-speed direct-current motor, ini Said contfol'cll'cuit mejans lncllldlflg a eluding an armature, a field-winding, a series compensat- Y conveftlng 0f Sa1d feverslble ing winding, 21 series cornmutating Winding, an auxiliary cltatlon'contfPhmg-p0W6! Into upldlrectlqnaljculfePt P cumulative commutating Winding, a means for applying 15 or and applying the same to said one or said resistancea reversible and variable direct-current eXcitation-controldevices ling-power to said field winding, and a rectifier-bridge for converting some of said reversable excitation-controlling- NO leferences cited

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