SU875543A1 - Device for indication of locations of short-circuitings of electric machine rotor steel sheets - Google Patents

Description

(54) DEVICE FOR INDICATION OF LOCKS OF STEEL SHEETS OF STEEL-STATOR ELECTRIC MACHINE

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The invention relates to a measurement technique and is intended for non-destructive control of the assembly operation of active steel stators of turbo-generators and synchronous compensators.

A device for indicating the locations of the steel sheets of the stator of an electric machine when magnetizing the stator with alternating current, containing a contact probe, is known. The contact probes have dimensions and weight, and are easy to operate.

However, these probes do not satisfy the requirements of the test technique due to the high inertia caused by the low thermal conductivity of the varnish film on the steel surface.

It is also known a device for indicating the closing points of sheets of a stator steel of an electric machine, comprising an infrared radiation receiver and a thermal compensation circuit for temperature fluctuations of the housing enclosed in a heat-conducting housing 2.

Receivers of infrared (IR) radiation can quantitatively measure the non-uniformity of heating of slightly heated surfaces by the intensity of radiation emitted by the surface in the infrared range, without direct contact with the surface.

The disadvantage of these devices is the effect on their readings of temperature fluctuations in the housing of the receiver of infrared radiation. To eliminate the resulting error, either the temperature control of the radiation receiver is applied in one way or another, or the introduction into the design of a measuring device of an exemplary heater, the radiation of which is compared with the radiation of the object being monitored.

However, the dimensions and weight of the known instruments are large, which makes it difficult to use them as a working tool of the tester. In addition, when using such devices for the purpose of testing machines, it is necessary to supply power to the working cavity of the stator, which complicates operation and violates safety requirements during testing.

The known scheme allows the correction without supplying a refrigerant agent and with a very low power consumption in the compensating circuit. However, the device has the following disadvantages:

1.Mala correction accuracy caused by the fact that the compensating circuit creates a voltage proportional to approximately the first degree of temperature (t) of the housing, whereas for a complete correction it is necessary to obtain the function of the AT type, where A is constant, and depending on the selected IR band -radiation, Inconsistency of the characteristics leads to instability of the zero position with significant fluctuations in the temperature of the housing.

2. The non-uniformity of heating of parts of the body, as well as the difference in thermal inertia of the radiation receiver and the compensating thermo-sensitive element, create conditions for the appearance of an additional non-stationary component voltage that simulates the appearance of an unstable effect of heating non-uniformity, additional thermocouples, due to the linearity of their characteristics do not completely eliminate errors. These drawbacks of the device do not interfere with its use as a stationary low-temperature pyrometer, but make it ineffective to use devices of this type for the purpose of testing machines, since the rapid and large fluctuations in ambient temperature characteristic of these tests mask a weakly controlled effect.

The purpose of the invention is to reduce the effect of fluctuations in ambient temperature.

To accomplish this goal, the device is equipped with a metal case enclosing a heat-conducting case, a metal handle for the operator, a heat insulating gasket installed between the cases, and a metal heat conductor connecting both cases at the point of attachment of the handle, and a window for transmitting radiation is provided in the metal case opposite the receiver to the receiver.

FIG. 1 shows a basic diagram of the device} in figure 2 a cross-section of the optical head.

The device consists of an optical head, which during the test is in the hand of the operator, and a measuring unit suspended from the belt. The optical head contains an infrared radiation receiver, a radiation thermoelectric element 1, a lens 2, a temperature-sensitive element 3, made in the form of windings, wound on the body 4, in which “repts these elements, a heat-insulating pad

5, a protective housing 6 with a metal handle 7 and a window, a heat conductor 8 through which the wires connecting the optical head and the measuring unit are passed. The measuring unit (Fig. 1) contains a bridge circuit 9, in one of the arms of which a multilink temperature-sensitive element 3, a voltage indicator 10 and an autonomous power source 11 are included.

The device works as follows.

The radiation from the controlled part of the object's surface passes through the lens 2 to the radiation thermoelement 1, causing a change in its temperature, as a result of which a heat flow is formed. This heat flow goes to the housing 4 and further through the heat conductor 8, the handle 7 to the operator’s body.

At the same time, a heat flux enters the protective housing b from the environment, which also flows through the handle 7 onto the operator’s body. The greater heat capacity and relatively stable temperature of the operator’s hand limits the temperature fluctuations of the housing 4 and receiver to narrower limits determined by the temperature difference protective housing b - medium and the ratio of the thermal conductivities of the protective housing 6 — the medium to the conductivity of the handle 7 of the housing 6 — is a hand that is much less than one.

The isothermality of the housing 4 is provided by selecting a material with a high thermal conductivity (aluminum) and shaping it into a short thick-walled cylinder, in the inner cavity of which the lens 2 and the radiation thermoelectric element 1 are located. The multi-link temperature sensing element 3 is made of copper and manganine wire and placed in the annular recess on the outer surface of the housing 4.

The voltage at the output of the 1st-unit temperature-sensitive element 3, depending on the temperature of the inner case, changes according to the law and KiTJ, where K is the conversion factor of element 3, LT is the change in temperature of the case 4.

With equal conversion factors of the thermosensitive element 3 and the I1C radiation receiver 1, under conditions of good smoothing of sharp fluctuations in the ambient temperature, a significant decrease in the error due to temperature changes of the receiver body 4 is provided. However, due to the close distance from the heated stator and the short time that is spent on inspection (5-10 minutes), the device is heated unevenly and the indicator arrow 10 is displaced 5. The presence of two bodies 4 and 6 and a heat-conducting handle 7 allows eliminate this phenomenon by heat removal from the operator’s body. Since the human body temperature is stable and the receiver casing 6 is all the time in the operator's hand, it is advisable to use it as a thermostat, i.e. The protective case 6 is black; the handle 7 transfers heat to the tester's hand. In order to remove heat coming from the stator through the window, a heat connection is provided to the operator's handle through the heat conductor 8 i handle 7. Thus, in the device I have with two thermal compensation schemes the multi-element temperature compensating element 3 and thermal stabilization due to the heat sink to the operator's body. The voltage generated by the radiation receiver is summed with the voltage of the unbalance of the bridge 9 and is indicated by the voltage indicator 10, which is located on the optical head and is constantly in the field of view of the operator. The indication of the closure of the stator sheets is performed as follows. Prior to the start of the test, the measuring circuit is pre-balanced by adjusting the arms of the bridge 9, in order for the voltage indicator 10 to be set to zero. After switching on, the magnetizing winding of the stator of the locking point of the steel sheets is heated more than the rest of the stator and, when viewing the surface, exhibits an increased intensity of radiation, indicated by the voltage indicator 10. Inspection of the stator is carried out by the operator, who holds the optical head in his hand and moves it under the surface of the stator. Since both housings 4 and b are separated from each other by a heat insulating pad over the entire surface except for the attachment point of the handle 7, where both housings 4 and 6 are connected with each other

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Fig. / Thermally through, the metal heat conductor 8, then due to this, attenuation of the direct thermal contact of the infrared radiation receiver body 4 with the environment is achieved. The use of thermal communication with the operator's hand, which has a biologically stable temperature, makes it possible to limit the temperature fluctuations of the receiver body 4, and the use of two heat insulated bodies 6 and 6 from each other increases the isothermality of the internal object. Limiting the thermal connection of the housings 4 and 6 to the gap filled with the thermal insulating gasket 5 makes it possible to further smooth out rapid temperature changes due to the resulting thermal inertia of the inner housing 4. Invention The device for indicating the closing points of the stator steel sheets of an electric machine containing an infrared radiation receiver and a bridge circuit for thermal compensation of variations in the temperature of the housing enclosed in a heat-conducting housing, characterized in that, in order to reduce There are no fluctuations in the ambient temperature, it is equipped with a metal case enclosing the heat-conducting case, a metal handle for the operator, a heat-insulating gasket installed between the cases, and a metal heat conductor connecting the two cases in the handle mounting site, while a window is made in the metal case opposite the primer. to transmit radiation to the receiver. Sources of information, rintye taken into account in the examination 1.Technology large electrical engineering. Part 1, Turbogenerators. M.-L., Energie, 1966. 2. US Patent 2.696.117, p. 73-355,1954.

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Claims (1)

Claim* A device for indicating the points of closure of the sheets of steel of the stator of an electric machine, containing an infrared radiation receiver and a bridge circuit for thermal compensation of body temperature fluctuations, enclosed in a heat-conducting body, characterized in that, in order to reduce the influence of fluctuations in ambient temperature, it is equipped with a metal body covering the heat-conducting body , a metal handle for the operator, a heat-insulating gasket installed between the housings, and a metal heat conductor connecting ba in the housing attachment point pen, the metal housing opposite the receiver has a window for the passage of radiation to the receiver.