SU121505A1 - Device for studying current oscillations in electrical circuits - Google Patents

Description

The subject of the invention is a device for studying current oscillations in electric circuits by oscillography or visually. A distinctive feature of this device is that a string is inserted into the chain, placed in a constant magnetic field. This ensures the selection of the frequencies to be studied.

The diagram shows, as an example, a schematic diagram of an instrument intended for measuring dynamic stresses in turbine blades and other structural elements of mechanisms during their operation.

The operation of the device is based on the Related Principle.

When the blade (or blade pack) is vibrated, elastic vibrations are excited in the rotor material. These vibrations propagate through the bearings into the stator and further into the turbine foundation. Elastic vibrations are transformed in a vibroprobe attached to the paws of the bearing into electrical oscillations that are applied to the amplifier.

If the vibrosh; the elastic vibrations were perceived only from the blade, in which the dynamic stresses are to be measured, then in this case it would be necessary to connect an electrical galvanometer at the output of the amplifier and to rub its scale in units of voltage, for example, in kg / cm.

However, in reality, all the elastic oscillations excited in the turbine by many sources will be perceived by the vibroshopper. Therefore, the solution to the problem of measuring dynamic stresses in an observed blade consists in extracting from the frequency spectrum a component that is excited only by the blade.

The use of electrical harmonic analyzers for this purpose does not give positive results, due to the low resolution of such analyzers.

In the proposed device for isolating the oscillations of the blade, a tuning steel string with high resolution is applied. In this case, the current from the amplifier passes

№ 121505

on a string fixed in two supports. The middle part of the string is in a constant magnetic field. The string is precisely tuned to a frequency equal to the frequency of oscillation of the blade. The magnitude of the dynamic stresses in the blade can be determined quite accurately from the swing of the string.

The device is arranged as follows.

Vibration strap 1 is mounted on the turbine stator, for example on the bearing legs. The wires from the vibrometer are connected to the amplifier 2. At the output of the amplifier, a tuning wire 5 is connected, at one end of which there is a micrometer screw 4 for changing the frequency of the vibration of the string. On the micrometer screw is placed the limb 5 with the scale indicating the frequency of oscillation of the string in hertz. A permanent magnet 6 is located in the middle of the string. An optical tube 7 is placed next to the magnetombs and has a scale for measuring the vibrations of the string.

Fluctuations of the string by means of a capacitive sensor 8 and amplifier 9 can be converted into electrical oscillations. A galvanometer // can be connected to the amplifier 9 by means of a switch 10, whose scale is drawn in units of voltage, or an oscilloscope loop 12 for recording oscillations.

If it is necessary to measure the dynamic stresses in the blades of several stages, you can use the switch to sequentially connect the required number of strings tuned to the corresponding frequencies of the blades to the amplifier 2 and make measurements, as indicated above.

Subject invention

A device for studying current oscillations in electrical circuits by means of oscillography or visually, characterized in that, in order to isolate the frequencies to be investigated, a tension string is placed in the circuit, placed in a constant magnetic field.

9 Yu