US2387588A - Synchronizing means for electric motors - Google Patents

Description

Oct. 23, 1945. R. J. JASSE SYNCHRONIZING MEANS FOR ELECTRIC MOTORS Filed Oct. 15, 1942 2 Sheets-Sheet 1 INVENTOR= RAYMOND JOSEPH JA55E BY a di f ATTOR NEY5.

Oct. 23,1945. R. J. JASSE 2,387,588

SYNCHRONIZING MEANS FOR ELECTRIC MOTORS Filed Oct. 15, 1942 2 Sheets-Sheet 2 Fig.4.

INVENTOR= RAYMOND JOEPH JASE .BY I M9 'ATTORNBY5.

Patented Oct. 23, 1945 SYNCHRONIZING MEANS FOR ELECTRIC MOTORS Raymond Joseph Jasse, Vichy, France; vested in the Alien Property Custodian Application October 15, 1942, Serial No. 462,134 In France December 10, 1940 3 Claims.

The present invention relates to electric motors the speed of which is rendered constant by being placed under the control of a standard tuningfork.

It is adapted to constitute a unit which ensures to the motor not only an average rigorously adjusted speed, but an instantaneous speed completely regular and independent in particular, of the voltage of the source of supply for the control, for instance, of measuring or recording apparatus.

The several objects and advantages of my invention will appear from the following description taken in connection with the accompanying drawings wherein:

Fig. 1 is a diagrammatic view showing circuit connections for regulating the speed of an electric motor.

Fig. 2 is a diagrammatic View showing the effects on the motor field, during an interval of time, due to the operation of the regulating contacts.

Fig. 3 is a diagrammatic view showing one preferred circuit arrangement.

Fig. 4 is a top plan view of one form of vibrator used in the circuit of Fig. 3.

Fig. 5 is a side elevation of the structure shown in Fig. 4.

Units are known which are constituted by a standard tuning-fork I (Fig. 1) and an electric shunt motor 2 the spindle of which carries a halfring 3 establishing the contact on a half of each revolution with the brush 4. The regulation takes place by the action of said intermittent contact 3-4 and of a second intermittent contact S-i established by the tuning-fork. The two intermittent contacts 3-4 and 5-H are mounted in parallel on the resistance 6 mounted in series on the inducing winding 1 and which is short-circuited when one or the other of the intermittent contacts 3-4 or 5-! is established.

will tend to be so much the more reduced as the short-circuit of the resistance 6 will be prolonged. In order that the motor should effect exactly one revolution when the tuning-fork effects a complete oscillation, it is necessary that the offsetting in the time of the establishment of both intermittent contacts should determine an average induction exactly corresponding to the speed thus defined.

If it is admitted that this condition is approximately satisfied, and if it is assumed that the speed of the motor has a tendency to increase. the breaking faces cm, (1'1, etc. of contact 5-i depending on the tuning-fork will remain the same. The establishing faces b0, b'o, etc. of contact 3- depending on the motor will tend to advance. The durations of the short-circuit b0 (11, b'o a'1, etc. will therefore have a tendency to increase. Consequently, the speed will tend to diminish until the average duration of the shortcircuit is brought to a Value which imparts to the motor the speed of synchronism. Conversely, any diminution of speed will have for effect to reduce the average duration of the short-circuit and, consequently, to bring back the speed to the value of synchronism. The unit therefore constitutes a synchronous regulator the average speed of which is determined by a tuning-fork the frequency of which is independent of the movements of the adjusted member and can be obtained with all the required accuracy.

The units which can be obtained with this diagram by utilising sustained tuning-forks having ordinary contacts present two inconveniences; if the average speed is exact this result is only obtained at the price of incessant variations of the instantaneous speed; furthermore, it is noticed In Fig. 2 has been shown the action of the two intermittent contacts 3-4 and 5-1. Line A shows in time the operation of the intermittent contact 5-! controlled by the tuning-fork; line B the operation of the intermittent contact 3-4 controlled by the motor; line C the short-circuits on the resistance 6 which result therefrom. The contact is established by the tuning-fork from as to m, then from ao to (1'1 from (1% to (1%, etc. It is established by the motor from ho to D1, from bo to b'l, etc. The resistance 6 will therefore be short-circuited, consequently, the current in the inducing winding '1 will be increased and the speed of the motor reduced from ho to (11, from I bo to ai, etc. The average speed of the motor that if the speed of the motor is, for any reason, considerable variations of potential for instance, appreciably different from syncln'onism, the latter can no longer be automatically re-established.

The invention has for object an improved unit constituted by a sustained vibrator of constant frequency, adapted to simultaneously obtain a displacement of the contact perfectly defined to the required frequency without superposition of bar monies, and a very high output of the sustaining magnetic circuit, and by a controlled electric motor provided with a speed limiting device intended to prevent the motor from racing and bringing back its speed to a value approximating synchronism.

Such a device allows of reducing the sustaining current to a very small value, without breaking spark, which ensures the cleanness of the contacts. It also ensures the perfect regularity of the instants of establishment and of breaking of the control contact, so that not only the average speed, but the instantaneous speed of the controlled motor remains constant. Finally, the regulator of the motor ensures a preliminary establishment of synchronism in such a manner that, in the event of falling out of tune, due for instance to an important Variation of the supply voltage,

the motor assumes by itself a speed sufiiciently near synchronism to allow the control to act.

It essentially consists in a sustained vibrator of constant frequency composed of two rigid beams carrying weights connected to the frame of the apparatus by springs of suitable rigidity and pivoting about their middle points, one of said beams carrying an armature and a contact; said armature is subjected to the action of a magnetic circuit provided with an inducing winding; said contact can supply, on the one hand, the inducing winding for sustaining the movement of said vibrator, on the other hand, a relay displacing a contact allowing, as is known, the control of an electric motor shunt field, which carries a centrifugal regulator establishing a contact in parallel with the contacts controlling said motor when the speed of said motor exceeds the speed of synchronism.

The invention will, in any case, be clearly understood by means of the following description and accompanying drawings, which is a diagram given, above all, by way of indication.

In Fig. 3, the vibrator 8 carries the sustaining contact 9, which is capable, during the displacement of the beam Ill, of touching the fixed contact H.

The contact thus established gives to the current of the cell l2, access:

1. To the resistance It, then to the magnetic winding M on which is mounted in parallel the condenser lb. The resistance 33 and condenser l are so calculated that between the current passing through the winding M and the movement of the contact 9 combined with the beam iii, a phase displacement is established which is approximately equal to a quarter of a period ensuring the sustaining of the vibration of the beam for the least consumption of electric energy.

2. To the resistance it, then to the winding ll of the telegraphic relay is, the armature of which thus moves by reproducing the establishments and breakings of the contact 9i i. A condenser I9 mounted in parallel on the winding 5 i avoids the production of breaking sparks at the contact 9-H i which would rapidly soil it.

The armature 21! of relay I8 is capable of coming in contact with the fixed contact 2!, establishing an intermittent contact which plays the part of contact 5! of Fig. 1. The use of this relay can be avoided by causing a contact directly established, to be directlycontrolled by the beam. It is preferable, however, to use a contact other than the vibrator contact as otherwise sparking at the vibrator contact may occur which can put the vibrator out of working order and modify its adjusting period. It is more preferable to use the intermediary of a relay which can be replaced or adjusted when its contacts are worn without inconvenience for the adjustment of the vibrator.

The motor 22 carries on the one hand, thehalfring 23 establishing the contact at every halfrevolution with the brush 2 3, on the other hand, a centrifugal regulator establishing the contact 25 per cent the speed of synchronism.

The three contacts 2fi2|, 23-44 and 25 are mounted in parallel on the resistance 26 mounted in series on the inducing winding 27 of the motor.

If the vibrator is assumed to be in action and sustained by the action of the contact 9-H and of the winding It, the relay l8, under the action of the current established by the contact 9-! I, vibrates at the period of the vibrator 8. Synchronism is established as above stated by the action of contact 2l playing the part of contact 5l, Fig. 1, and of contact 23-24 playing the part of contact 3-4, Fig. 1. If the motor has a tendency to race, its speed is maintained by the action of contact at a value sufilciently near synchronism for the latter to be established.

Figs. 4 and 5 clearly define the principle of the sustained vibrator. The frame 28 (Fig. 4) carries, through the medium of a common suspension spring 29, the two balanced beams 39 and 3| respectively carrying the weights 32 and 33. A common spring 35 is attached to both beams symmetrically at the points 35 and 35 and to the frame at the point 31.

The beam 30 carries (Fig. 5) a relay armature 38. On said armature is secured by means of a flexible blade 39 a movable contact 40 capable of touching a fixed contact ll accurately adjustable in position by means of the micrometer screw 42.

When the contact 4tl ll is established, the current from the cell I2 is sent, through the medium of resistance [3, in the inducing winding l6 Fig. 3 (43 Fig. 5). The differential magnetic circuit 44, polarized by the permanent magnet 45, attracts the armature 38 so as to cause the beam 33 to rock in clockwise direction. The attraction ceases when the contact til-4| is broken. Owing to the system constituted by the resistance l3, the coil of the relay and the condenser I5, the estab- 40 lishment of the attraction and its interruption possess a definite lag on the establishment and the breaking of the sustaining contact ii ll. The phase displacement necessary for ensuring sustaining is thus obtained. Due to the presence of condenser I9 no spark is produced at the contacts. The relay equipment having a high electromechanical output, a very small current is suflicient for sustaining the oscillations. The contacts and 4| therefore work in excellent conditions and, in practice, last indefinitely.

The system reduced to the beam 36 equipped with the dead-heads 32 and spring 34 sustained by the relay Fig. 5 would sufiice for constituting a vibrator of definite frequency. However, it has a very serious inconvenience: it begins to oscillate only if the frame of the relay is very heavy and its period depends on the bulk of said frame. It is even modified if the frame is moved from one table to another.

It is in order to remedy this inconvenience, the frame carries a second beam 3| equipped with two weights 33 and a spring 34. This unit is tuned so as to give the same period of vibration as the unit of the beam 30. When the latter begins to vibrate, it drives, by the action of the fiexibilities of the connection members, the synchronous beam 35 which begins to oscillate in the reverse direction, balancing for the greater part the oscillation of beam 36. The common oscillation reaches a great amplitude and the period is rendered independent of the suspension of the frame.

I claim:

1. In a device for maintaining constant speed of an electric motor, a sustained vibrator comprising a support, a balanced beam carrying end tilting of one beam produces tilting of the other beam in the opposite direction.

2. The device claimed in claim 1 wherein the support for said beams is a torsional spring.

3. The device as claimed in claim 1 wherein the means connecting the beams is a torsional spring.

' RAYMOND JOSEPH JASSE.

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