SU756536A1 - Ac generator protecting device - Google Patents

Description

The invention relates to electrical engineering and can be used in devices for protecting alternators from overloads and short circuits. five

A device is known for protecting alternators from overloads and short circuits with a measuring element made using current transformers [ΐ]. one*

It is also known a device of maximum current protection, containing three current transformers in the quality of a measuring element, three electromagnetic current relays, a time relay and an actuator [2].

The presence of three current transformers, three current relays cause a considerable weight and dimensions of the protection device. 2C

The purpose of the invention is to simplify the protection device of the alternator.

This goal is achieved by the fact that in the protection device of the alternating current generator 25, containing a measuring element connected to the actuating element, the measuring element is designed as an additional winding laid on.

2

the stator in some slots with the main winding, while the number of pairs of poles of the additional winding is an odd number of times greater than the number of pairs of poles of the main winding of the generator.

FIG. 1 is a schematic diagram of an alternator protection device; in fig. 2 - the same, with a multi-phase measuring element.

The protection device contains a measuring element 1 connected to the winding 2 of the actuating element 3, the contacts 4 of which are included in the main winding circuit of the generator 5

6. The measuring element (additional winding) 1 is placed on the stator of the generator 6 in the same grooves with the main winding 5.

The measuring element can be made both single-phase and multi-phase. The protection device (figure 2) contains a multi-phase, for example, three-phase, measuring element 1, connected through the converter 7 to the winding 2 of the actuating element 3, the contacts 4 of which are included in the main winding circuit 5 of the generator 6.

756536

Transducer 7 serves to match the characteristics and parameters of the measuring element 1 and the executive protection element 3. As a converter 7, a transformer, a rectifier or a combination thereof can be used.

Since the principle of operation of the protection devices shown in FIGS. 1 and 2 is similar, we consider their work on the example of the device shown in FIG. 1. When the load current of the main winding 5 of the generator 6 increases, the EMF of the measuring element 1 increases. As soon as the signal of the measuring element 1 reaches a predetermined value, the actuating element 3 operates, which by its contacts 4 turns off the main winding 5 of the generator 6.

The magnitude of the EMF of the measuring element 1 is determined by the load of the main winding 5 of the generator b, which can be explained as follows. Since the measuring element 1 represents an additional winding, made, for example, for the tripled number of polar poles in relation to the main winding 5 of the generator 6, the signal magnitude on the measuring element 1 is determined by the relative content of the third harmonic of the induction in the air gap of the generator 6 .

_E

V in /

where Ml and K are the number of turns and the winding ® ® coefficient of the additional winding (measuring element 1);

М £ и - the number of turns and winding ¹ nd the main winding coefficient 5

E | - EMF main winding 5;

- the relative content of the third induction harmonic in the air gap of the generator 6, depending on the magnitude of the load of the main winding 5.

With an increase in the load of the main winding 5 of the generator 6, the armature response becomes demagnetized by the fundamental harmonic B *, and magnetizing by the third harmonic B30. It /

- leads to an increase in the relative content of the third harmonic of induction in the air gap of the generator 6 and a proportional increase in the EMF of the measuring element 1 with increasing load current.

In case of a sudden short circuit of the main winding 5 of the generator b, the signal on the measuring element 1 also increases in proportion to the increase in the short circuit current,

15 which triggers the protection.

The implementation of the measuring element 1 in the form of additional winding reduces the weight and dimensions of the protection device of the alternator.

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Claims (2)

Claim 1. A device for the protection of an alternating current generator, containing a measuring element connected to the actuator element, characterized in that, in order to facilitate the protection of the alternator device measurable ^30-negative element is a further winding, arranged on the stator in the same grooves with the main winding, wherein the number of pairs of the additional winding poles an odd ³³ times the number of pole pairs of the generator main winding. 2. The device according to claim 1, characterized in that the measuring element is made in the form of a multi40 additional phase winding connected to the actuator via a converter.