SU1744764A1 - Device for protection of electric machine against humidification - Google Patents

Abstract

The essence of the invention: the device contains a humidity sensor. It is made in the form of two conductors 4.5 of high-resistance material. The ends of 6.8 conductors are separated by a porous gasket 7 and placed near the winding. Opposite ends of the conductors are placed in heat-resistant insulation and connected to the output studs of the electric machine. 2 Il.

Description

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This invention relates to electrical engineering, in particular, to protecting electrical machines of alternating and direct current from decreasing insulation resistance.

A known three-phase electric machine with an integrated unit for protection against damage to the stator winding, including a protection unit, is made inside the electric machine so that the ring plane is perpendicular to the axis of rotation of the rotor, and its geometric center is on this axis.

Closest to the present invention is a device for protecting a three-phase electric motor from abnormal modes, comprising a switching device, a winding of an electric machine, the ends of which are connected to the output studs of the terminal box, and a humidity sensor made in the form of a ring placed near the winding, the output of which is connected in the protection scheme.

However, the first of these known devices protects the winding from further propagation of damage already occurring in the winding, and the second has a low reliability and complex structure. If there is a leakage of current from the humidity sensor (coil attached to the winding frontal part) to the housing, then it (leakage) does not appear from the winding to the housing or between the windings of different windings that are under great potential and their breakdown between them is greater then the protection will be somewhat late. In addition, connecting the case of an electrical machine with the phase of the mains supply, even through the thyristor when it is closed, is not the best protection option. Coincidence is not excluded when the thyristor is punched and it is on this electric motor that the ground conductor is broken, and this is very dangerous for the maintenance personnel.

The complexity of the design, a large number of elements, the additional laying of wires to the electric machine and not guaranteed safety precautions significantly impede the introduction of a known technical solution.

The aim of the invention is to increase reliability and simplify the design.

The goal is achieved by the fact that the humidity sensor is made in the form of two conductors, one ends of which are separated by a porous gasket and placed near the winding of the electric machine, and the second ends of the conductors are connected to the output studs of the terminal box, and laying attached

properties dramatically change their conductivity due to changes in humidity.

FIG. 1 shows the stator of the electric machine with the placement in the lower part of the humidity sensor; in fig. 2 - moisture sensor design.

The proposed device includes a humidity sensor 1 placed in the free space under the winding 2 of the stator 3 of the electric machine. The humidity sensor (see Fig.2) is made in the form of conductors 4 and 5, made of high resistance material, such as nichrome, with the end 6 of the conductor 5 wound on the outer side of the porous strip 7, and the end 8 of the conductor 4 is placed in the center inside the porous strip.

Opposite ends of the conductors are placed in heat-resistant insulation, for example, in silicone tubes, and connected to lead pins of the 9 terminal box of the electric machine.

The porous gasket is made of fibrous non-combustible material, such as asbestos, fiberglass, etc., and is impregnated with a substance that has the property of being a dielectric in a dry form and a conductor in a wet state. Such properties have, for example, salt, potash, etc.

The device works as follows.

In a normal (not wet) environment, the device does not have any effect on the object of protection, for example, an electrical machine.

When the ambient humidity is significantly exceeded, for example, rupture of pipelines, steam lines, etc., water or steam, the winding 2 and the humidity sensor 1 placed in the cavity of the stator 3 are wetted by the electric machine case and penetrate into the gaps of its mating components. under the winding of an electric machine.

The preemptive actions of the humidity sensor are ensured by the absence of a moisture-proof coating, while the winding of the electric machine has such protection. In addition, the porous gasket 7 is given the properties to drastically change its conductivity from a change in humidity, therefore when moisture enters the winding and the humidity sensor, an electrical breakdown between the end 6 of the conductor 5 and the end 8 of the conductor 4, separated by a porous pad, will occur much earlier than waterproof turns of the winding.

Electrical breakdown of a porous gasket will cause a sharp increase in the current in the circuit of high-resistance conductors 4 and 5 connected to the output pins 9 of the terminal box of the electric machine. A sharp increase in current close in magnitude to the short-circuit current (the current is limited by conductors 5 and 6 made of high-resistance material) will trigger a protection, for example, switching off an AP-50 switching device, etc. installed in the main circuit of an electric machine .

The use of conductors 4 and 5 of high-resistance material contributes to the limitation of current in the circuits of maintaining the switching apparatus and the elimination of deep-fitting voltage in low-power networks, such as rural networks with low-power transformers.

Reactivation of the device is achieved by jointly drying it with an electric machine or replacing its porous gasket.

The use of the proposed device makes it possible to prevent the breakdown of the windings of AC and DC electric machines in an easy and reliable way.

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Claims (1)

Claims of invention An electric machine protection device against humidification, comprising a humidity sensor whose output is connected to a protection circuit, characterized in that, in order to increase reliability and simplify the design, the humidity sensor is made in the form of two conductors of high-resistance material, one ends of which are separated by a porous gasket and are intended to be placed close to the winding of the electric machine, while the other ends of the sensor conductors are intended to be connected to the output studs of the terminal box, while It is made of a material whose conductivity drastically changes with humidity. five 0 25 9 1