US1251669A - Stroboscopic device. - Google Patents

Description

G. JENSEN.

STROBOSCOPIC DEVICE.

APPLICATION nuzp OCT. 9. ms.

1,251,669, Patented Jan. 1, 1918.

WITNESSES: M ly INV ENTOR W e 51/ 71 nan/015a I A ORNEY UNITED STATES PATENT OFFICE.

GUNNAR JENSEN, OF SWISSVALE, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

STROBOSCOPIC DEVIGE.

Specification of Letters Patent.

Application filed October 9, 1915. Serial No. 54,949.

To all whom it may concern: 7

Be it known that I, GUNNAR JENSEN, a citizen of the United States, and a resident of Swissvale, in the county of Allegheny and State of Pennsylvania, have invented anew and useful Improvement in Stroboscopic Devices, of which the followingis a specification.

My invention relates to stroboscopic devices and particularly to. devices that are used to determine the percentage slip of alternating-current dynamo-electric machines.

The object of my invention is to provide a device, of the above indicated character, that is simple in construction and accurate over a wide range of application.

The single figure of the accompanylng drawings is a perspective view of a strobescopic device embodying my invention.

A dynamo-electric machine l'is connectedto an alternating-current circuit 2, and a stroboscopic device 3 1s electrlcally connected to the circuit 2 and mechanicallyv connected to the rotor 4 of the dynamoelectric machine 1 for the purpose of determining the percentage sllp thereof.

The stroboscopic device 3 comprises a sup- 7 porting standard 5, avibrating device 6 and a gear box 7. The vibrating device 6 comprises a magnetizable core member 8, a winding 9 and a resilient armature 10. The armature 10 is supported by a block 11, and its effective length is so varied that its period of vibration is normal with respect to the frequency of the alternating current that traverses the winding 9. The block 11 surrounds the standard 5 and is provided with a thumb screw 12 for the purpose of securing it in position. The magnetizable core member 8, a resistor 13 and an electric lamp 14 are also supported by the block 11. The lamp 1 1 is provided with a refiector 15 for the purpose of illuminating- 18 and 19 that are spaced apart by spacing Patented J an. 1, 1918.

members 20. Journaled in the plates 18 and 19 are three shafts or spindles 21, 22 and 23. A gear wheel 24 is mounted upon the shaft 21, as is also a disk 25. The disk 25 is provided with oppositely disposed rad1al slots 29 the number of which is an integral factor of the number of poles in the machine-1. The gear wheel 24 is provided with twenty-five teeth and is adapted toen- -gage two gear wheels 26 and 27 that aremounted on the shafts 22 and 23, respectively. The gear wheels'26 and 27 are provided with twenty-three and twenty-four teeth, respectively. However, the gear wheels may have various numbersof teeth, accordlng to the ratios desired. A universal couphng 28 is adapted to connect the rotor 4 of the machine 1 to any one of the shafts 21, 22 and 23.

If the coupling 28 is 'connected to the.

shaft 21 the disk 25 will be rotated at the same speed as the rotor of the machine 1, and, if the rotor of the machine 1 .rotates at synchronous speed the armature 10 will appear in the same position each time, when viewed through the openings 29 in the disk 25, or, 'in other words, the armature 10 will apparently stand still. However, if the rotor 4 is rotated at a speed slightly different from that of synchronism, the armature 10 will be found in a slightly different position ateach observation and will apparently oscillate from side to side, similar to a pendulum. Since the armature oscillates in synchronism with the circuit 2, the apparent oscillations of the same will correspond to the slip in alternations, and the slip will be equal to the apparent oscillations per minute divided by the frequency of the circuit in alternations per minute.

It is evident that the greater theslip the greater will be the number of apparent oscillations of the armature, and, if the slip is very high, these will become so rapid as to be impossible to determine accurately. It has been found, by numerous trials, that about 150 oscillations per minute is the maximum that can be ordinarily observed with accuracy. However, if the machine l is a sixty-cycle machine, 150 oscillations per minute will correspond to 2.08 per cent. slip. Since a large proportion of sixty-cycle machines have a percentage slip varying from two to eight or more, I provide the gear box 7 by means of which the disk 25 may be rotated at a speed that is a predetermined definite amount lower than the speed of the. rotor 4, thus permitting higher s'lip values to be accurately determined. When the rotor 4 is connected to the shaft-23 the disk 25 will rotate four per cent. slower than the rotor 4, and, thus, if the armature 10 appears to stand in one position when observed through the openings 29, the'slip of the rotor 4 will be four per cent. If the rotor 4 is connected to the shaft 22 the disk 25 will be rotated at a speed that is eight per cent. lower than the speed of the rotor 4, and, if the armature 10 appears to stand still when observed through the openings 2, the .slip of the rotor 4 will be eight per -cent. Thus, with the gear ratios, as sh own,

four per cent. and eight per cent. may be taken as reference points, and the slip above and below these particular values may be determined and added or subtracted from either 4 or 8 to obtain the true percentage slip. Assuming that the rotor 4 is connected to the shaft 23, the percentage slip equals 4 plus or minus, the observed oscillations perv minute divided b the frequency of the circuit 2 in alternations per minute. Whether the sign is plus or minus may be readily determined by varying the load upon the machine 1 and noting whether the oscillations.

increase or decrease with an increase in load. If the oscillations decrease, 1t 1s evident that the percent. slip isunder 4 or that the sign is minus.

The disk 25 may be provided with any number of openings 29, according to the number of poles in the machine 1, and the ratio of the gear wheels 24, 26 and 28 may be varied according to the range of slip to be determined.

The vibrating portion 6 and the gear box 7 are adapted to be moved along the supporting standard 5 for the purpose of facilitating observation and for facilitating the connections of the device to the'rotor of the machine to be tested.

My invention is not limited to the particu lar construction illustrated, as many modifications may be madetherein without departing from the spirit and scope of the invention as set forth in the appended claims.

I claim as my invention:

1. 'In a stroboscopic device for an alternating-current motor, the combination with a supporting standard, a vibratory member, and means adjustable along the standard for for actuating the same in synchronism with the alternating current, of a rotatable disk adjustably mounted on the standard, and a universal connection between the rotatable disk and the motor.

3. In a stroboscopic device for a dynamo- 'electric machine, the combination with a supporting standard, and a vibratory member adjustable to various positions along the standard, of a rotatable disk having openings therein, means for operatively connecting the rotatable disk to the machine, and means for adjusting the position of the disk with respect to the vibratory member.

4. In a stroboscopic device for an altermating-current motor, the combination with a supportingstandard and a vibrating membar that is vibrated at the frequency ot the alternating current, of a rotatable disk having slits therein, a gearing operatively connected to the disk and the rotatable member of the motor for driving the disk either in synchronism with the rotatable member or in a predetermined speed relation therewith, and means for adjustably securing the vibrating member, rotatable disk and the gearing to the supporting standard.

5. In a stroboscopic device for an alternating-current motor, the combination with a supportin standard, a vibratory member adapted to e vibrated in synchronism with the alternating current, and means for securing the vibratory member to various positions along the standard, of a rotatable disk, and a gear mechanism operatively connected between the disk and the movable member of. the motor and supported by the standard.

6. In a stroboscopicdevice for an alternating-current motor, the combination with a supporting standard, a vibratory member adapted to be vibrated in synchronism with the alternating current, and means for attaching the vibratory member to the supporting tandard, of a rotatable disk, a gear mechanism operatively connected between the disk and the movable member of the motor, and means for adjusting the position of the disk with respect to the supporting standard.

7. In a stroboscopic device for an alternating-current motor, the combination with a supporting standard, a vibratory member adapted to be vibrated in synchronism with the alternating current, and mean for attaching the vibratory member to the supporting standard, of a gear box, a disk ro- 5 tatably mounted on the gear box, a gear mechanism within the gear box, means for connecting the gear mechanism to the rotatable member of the motor and means for shifting the position of the gear box along the supporting standard.

In testimony whereof, I have hereunto subscribed my name this 28th day of Sept,

GUNNAR JENSEN.

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