CN220381255U

CN220381255U - Detection accessory and detection system for three-phase motor star sealing circuit

Info

Publication number: CN220381255U
Application number: CN202321958436.2U
Authority: CN
Inventors: 余刚; 陈佳颖; 冯大成; 张东进; F·阿拉布
Original assignee: Schneider Electric China Co Ltd
Current assignee: Schneider Electric China Co Ltd
Priority date: 2023-07-24
Filing date: 2023-07-24
Publication date: 2024-01-23
Anticipated expiration: 2033-07-24

Abstract

The utility model relates to a detection accessory for a three-phase motor star-sealing circuit, which comprises: the first transformer comprises a first iron core, a first primary winding and a first secondary winding, wherein the first primary winding and the first secondary winding are arranged on the first iron core; the current supply unit is connected in series with the first primary winding and is used for supplying primary current to the first primary winding; the first voltage detection unit is connected with the first secondary winding in parallel and is used for detecting first secondary voltages at two ends of the first secondary winding, wherein the first secondary winding is used for being connected with a first branch of the star sealing circuit of the three-phase motor in series. The utility model also relates to a detection system for the three-phase motor star-sealing circuit, which comprises the detection accessory and the three-phase motor star-sealing circuit, wherein the three-phase motor star-sealing circuit comprises three branches, and each branch comprises a motor winding and a contact switch for the corresponding branch in a star-sealing contactor which are connected in series.

Description

Detection accessory and detection system for three-phase motor star sealing circuit

Technical Field

The utility model relates to the field of circuit detection, in particular to a detection accessory and a detection system for a three-phase motor star-sealing circuit.

Background

For example, in elevator operation, the star-sealing technique of the motor is often used as a safety measure. The star sealing technology is that when the elevator loses power supply, the main contactor is opened and the star sealing contactor is closed, so that the star sealing contactor and the motor winding form a passive loop. This is based on that, when the elevator is actively shut down or when a failure such as a failure of the main power supply or a failure of the circuit occurs in the elevator, the permanent magnet synchronous hoisting machine serving as a motor rotates before the elevator is stopped, and the main contactor is opened and the star contactor is closed, so that the three-phase windings of the hoisting machine are shorted, and the mechanical torque and the electromagnetic torque of the hoisting machine are balanced, thereby reducing the speed of the elevator and improving the safety of the elevator.

Therefore, for the normal application of the star sealing technology, whether the star sealing circuit is normal is important. However, the star-sealed circuit is used as a backup protection circuit, and whether the star-sealed circuit is complete or not does not influence the daily operation of the elevator. In the case of abnormal star-sealing circuit due to failure such as disconnection of the star-sealing circuit or failure of the star-sealing contactor, the elevator operator cannot actively learn the information in time, and serious consequences can be caused once abnormal movement of the elevator, such as top-rushing or bottom-rushing, occurs.

At present, the detection of the star sealing circuit judges whether the star sealing circuit is normal or effective by letting an elevator slide and measuring the speed of the elevator, but the detection needs to be tested on a specific floor, and the method is tedious and expensive.

Disclosure of Invention

In order to solve the problems, the utility model provides a detection accessory for a three-phase motor star-sealing circuit, which can be realized in an integrated and miniaturized manner, and a detection system formed by the detection accessory, wherein the detection accessory can be directly installed on an existing star-sealing contactor without modifying the star-sealing circuit, so that simple, efficient and accurate detection of the three-phase motor star-sealing circuit is realized.

The embodiment of the utility model provides a detection accessory for a three-phase motor star sealing circuit, which comprises the following components: the first transformer comprises a first iron core, a first primary winding and a first secondary winding, wherein the first primary winding and the first secondary winding are arranged on the first iron core; the current supply unit is connected in series with the first primary winding and is used for supplying primary current to the first primary winding; the first voltage detection unit is connected with the first secondary winding in parallel and is used for detecting first secondary voltages at two ends of the first secondary winding; the first secondary winding is used for being connected with a first branch of the star sealing circuit of the three-phase motor in series.

According to an embodiment of the utility model, the first transformer further comprises a second secondary winding and a third secondary winding arranged on the first core, and the detection accessory further comprises: the second voltage detection unit is connected with the second secondary winding in parallel and is used for detecting second-stage voltages at two ends of the second secondary winding; the third voltage detection unit is connected with the third secondary winding in parallel and is used for detecting the third secondary voltage at two ends of the third secondary winding; the second secondary winding is used for being connected in series with a second branch of the three-phase motor star sealing circuit, and the third secondary winding is used for being connected in series with a third branch of the three-phase motor star sealing circuit.

According to an embodiment of the utility model, the detection accessory further comprises: the second transformer comprises a second iron core, and a second primary winding and a second secondary winding which are arranged on the second iron core; the third transformer comprises a third iron core, and a third primary winding and a third secondary winding which are arranged on the third iron core; the second voltage detection unit is connected with the second secondary winding in parallel and is used for detecting second-stage voltages at two ends of the second secondary winding; the third voltage detection unit is connected with the third secondary winding in parallel and is used for detecting the third secondary voltage at two ends of the third secondary winding; the second secondary winding is used for being connected in series with a second branch of the three-phase motor star sealing circuit, and the third secondary winding is used for being connected in series with a third branch of the three-phase motor star sealing circuit.

According to an embodiment of the present utility model, the first primary winding, the second primary winding, the third primary winding and the current supply unit are connected in series.

According to an embodiment of the present utility model, the first primary winding, the second primary winding, and the third primary winding are connected in series with the current supply unit, respectively.

According to an embodiment of the utility model, the detection accessory further comprises: and the first end of the selection switch is connected with the first end of the first secondary winding, the second end of the first secondary winding is connected with the first branch, and the second end of the selection switch is switchably connected with the second branch and the third branch of the star sealing circuit of the three-phase motor.

According to an embodiment of the utility model, the detection accessory further comprises: the first end of the first selection switch is connected with the first end of the first secondary winding, the first end of the second selection switch is connected with the second end of the first secondary winding, and the second end of the first selection switch and the second end of the second selection switch are switchably connected with different branches of the star sealing circuit of the three-phase motor respectively. According to an embodiment of the utility model, the number of turns of the primary winding and the secondary winding is less than 10 turns.

The embodiment of the utility model provides a detection system for a three-phase motor star-sealing circuit, which comprises the following components: a three-phase motor star-seal circuit comprising three legs, each leg comprising a motor winding connected in series and a contact switch for the corresponding leg in a star-seal contactor, and a detection accessory according to one of the embodiments of the present utility model for detecting a three-phase motor star-seal circuit.

According to an embodiment of the utility model, the detection system further comprises: the control module is used for controlling the on or off of a contact switch of the star sealing contactor and realizing the detection of the star sealing circuit of the three-phase motor based on a secondary voltage signal output by the detection accessory.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings used in the description of the embodiments will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary embodiments of the present utility model, and that other drawings may be obtained from these drawings without inventive effort to those of ordinary skill in the art.

FIG. 1 shows a schematic diagram of the connection of a three-phase motor star circuit;

FIG. 2 shows a schematic diagram of a detection accessory according to an embodiment of the present utility model;

FIG. 3 shows a schematic diagram of a detection accessory and its detection system according to another embodiment of the present utility model;

FIG. 4 shows a schematic diagram of a detection accessory and its detection system according to another embodiment of the present utility model;

FIGS. 5A, 5B show schematic views of a primary side connection of the test accessory according to FIG. 4;

fig. 6 shows a schematic diagram of a detection accessory and its detection system according to another embodiment of the present utility model.

Detailed Description

In order to make the objects, technical solutions and advantages of the present utility model more apparent, exemplary embodiments according to the present utility model will be described in detail with reference to the accompanying drawings. It should be apparent that the described embodiments are only some embodiments of the present utility model and not all embodiments of the present utility model, and it should be understood that the present utility model is not limited by the example embodiments described herein.

In the present specification and drawings, steps and elements having substantially the same or similar are denoted by the same or similar reference numerals, and repeated descriptions of the steps and elements will be omitted. Meanwhile, in the description of the present utility model, the terms "first", "second", and the like are used only to distinguish the description, and are not to be construed as indicating or implying relative importance or order.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this utility model belongs. The terminology used herein is for the purpose of describing embodiments of the utility model only and is not intended to be limiting of the utility model.

Fig. 1 shows a schematic diagram of the connection of a three-phase motor star circuit.

As shown in fig. 1, the main power module PS may supply power to the motor windings MW of the three-phase motor via the main contactor KMY. The motor winding MW is schematically star-connected with three windings OU, OV, OW. In the event of an active shut-off of the main power module PS or a fault in the supply circuit, the main contactor KMY is opened and the star-close contactor KAY is closed.

The star-seal contactor KAY may have, for example, three contact switches CO1, CO2, CO3, corresponding to the three windings OU, OV, OW of the motor winding MW, respectively. The star-sealed contactors KAY are connected at one end to the corresponding windings and at the other end, for example at K1, K2, K3, to each other. Thereby forming three branches of the three-phase motor star-sealing circuit: for example, a first branch OK1, comprising a first contact switch CO1 and a first winding OU; a second branch OK2 comprising a second contact switch CO2 and a second winding OV; the third branch OK3 comprises a third contact switch CO3 and a third winding OW.

The motor winding MW is short-circuited by the opening of the main contactor KMY and the closing of the star-sealing contactor KAY, so that a three-phase motor star-sealing circuit is formed.

It should be understood that the expressions "first", "second", "third", etc. are used merely to distinguish between different objects and are not intended to be limiting. For example, according to an embodiment of the present utility model, the first leg may also represent leg OK2 or leg OK3.

Fig. 2 shows a schematic diagram of a detection accessory according to an embodiment of the utility model.

As shown in fig. 2, the detection accessory CT includes a transformer including a core C and a primary winding PW and a secondary winding SW arranged on the core C.

The detection accessory CT further includes a current supply unit CS connected in series with the primary winding PW for supplying the primary winding PW with an alternating primary current. For example, the current supply unit CS may include a power source such as a 24V dc power source and a modulator such as a high frequency waveform generator.

The detection accessory CT further comprises a voltage detection unit VD connected in parallel with the secondary winding SW for detecting a secondary voltage across the secondary winding SW. The voltage detection unit VD is, for example, a voltmeter.

The secondary winding is arranged for series connection with a branch of a three-phase motor star circuit, as described in more detail below with respect to the detection system. When the detection is performed, the electric machine is in a stationary state, i.e. in a non-operating state, which acts neither as a motor nor as a generator. A passive star-sealing circuit is formed by the star-sealing contactor, the motor winding and the secondary winding of the detection accessory by opening the main contactor and closing the star-sealing contactor.

In the detection accessory CT, an alternating primary current may be supplied to the primary winding PW through the current supply unit CS, an alternating magnetic flux is generated in the core CS according to the electromagnetic induction principle, and thus an induced electromotive force is generated in the secondary winding SW. The voltage detection means VD detects the electromotive force difference, that is, the voltage across the secondary winding SW.

Under the condition that the star sealing circuit is normal, the three branches and detection accessories respectively connected with the branches in series can be conducted, and the voltages at two ends of the secondary winding SW are normal. In the case of abnormal star circuit, at least one branch is not conducted, and the secondary winding connected in series with the branch cannot generate current and cannot generate magnetic potential for balancing the primary current, so that the voltage across the secondary winding is obviously higher than that in the normal case. Therefore, the three branches or the star-sealing circuit can be detected according to the secondary voltage signal detected and output by the detection accessory.

In the detection using the detection accessory of the present embodiment, the detection accessory includes, for example: a first transformer including a first core and a first primary winding and a first secondary winding disposed on the first core; a current supply unit connected in series with the first primary winding for supplying a primary current to the first primary winding; the first voltage detection unit is connected with the first secondary winding in parallel and is used for detecting first secondary voltages at two ends of the first secondary winding, wherein the first secondary winding is used for being connected with a first branch, a second branch or a third branch of the three-phase motor star sealing circuit in series. In this way, each branch in the star circuit is detected in multiple passes.

Fig. 3 shows a schematic diagram of a detection accessory and its detection system according to another embodiment of the utility model. The detection system consists of a three-phase motor star-sealing circuit comprising a star-sealing contactor KAY and a motor winding MW and a detection accessory TC.

As shown in fig. 3, the detection accessory TC includes a first transformer IT1. The first transformer IT1 includes a core and three secondary windings, i.e., a first secondary winding SW1, a second secondary winding SW2, and a third secondary winding SW3, disposed on the core. The detecting accessory TC further includes three voltage detecting units, not shown, respectively corresponding to the three secondary windings, which are respectively connected in parallel with the corresponding secondary windings and are used for detecting the secondary voltages across the corresponding secondary windings.

The first secondary winding SW1 is connected at one end to the terminal K1 of the first contact switch OA1 of the star seal contactor KAY, the second secondary winding SW2 is connected at one end to the terminal K2 of the second contact switch CO2, the third secondary winding SW3 is connected at one end to the terminal K3 of the third contact switch CO3, the other end K1' of the first secondary winding SW1, the other end K2' of the second secondary winding SW2, and the other end K3' of the third branch OK3 are shorted, whereby the first secondary winding SW1 is connected in series with the first branch OK1 of the three-phase motor star seal circuit including the first contact switch CO1 and the first winding OU, the second secondary winding SW2 is connected in series with the second branch OK2 including the second contact switch CO2 and the second winding OV, and the third secondary winding SW3 is connected in series with the third branch OK3 including the third contact switch CO3 and the third winding OW. For example, the first branch OK1 along with the line K1K1' may form a first loop with the second branch OK2 along with the line K2K2', the second branch OK2 and the third branch OK3 and the line K3' may form a second loop, and the third branch OK3 and the line K3' and the first branch OK1 and the line K1' may form a third loop.

The detection accessory CT further includes a primary winding and a current supply unit, which are not shown.

By closing the contact switch of the star-sealed contactor and supplying the primary winding with current by means of the current supply unit, the respective voltage can be measured on the secondary winding side.

In the case where the first branch OK1 is abnormal or open, the first loop and the third loop including the first branch OK1 are not turned on, and the second loop is turned on, so that the voltages across the second and third secondary windings SW2 and SW3 both show a normal lower voltage, and the voltage across the first secondary winding SW1 shows an abnormal higher voltage.

In the case that the second branch OK2 is abnormal, the first loop and the second loop including the second branch OK2 are not turned on, and the third loop is turned on, so that the voltages across the first and third secondary windings SW1 and SW3 both represent a normal lower voltage, and the voltage across the second secondary winding SW2 represents an abnormal higher voltage.

In the case where the third branch OK1 is abnormal, the second loop and the third loop including the third branch OK3 are not turned on, and the first loop is turned on, so that the voltages across the first secondary winding SW1 and the second secondary winding SW2 both represent a normal lower voltage, and the voltage across the third secondary winding SW3 represents an abnormal higher voltage.

The relationship between the voltage across the secondary winding and the state of the branch is more clearly shown below in table 1:

table 1: relationship between voltage across secondary winding and state of branch

In table 1, "high" indicates an abnormally high voltage across the secondary winding, and "low" indicates a normally low voltage across the secondary winding. The "high" and "low" do not represent absolute magnitudes, but rather represent relative relationships in the abnormal and normal conditions of the star circuit.

To determine the "high" voltage signal and the "low" voltage signal, for example, the normal secondary winding voltage can be detected as a reference voltage in a star circuit that is determined to be normal. If, at the time of detection, the detection accessory outputs a voltage higher than the reference voltage, an abnormal branch is considered to occur. Alternatively, the reference voltage may not be acquired in advance, but the judgment may be made directly using the voltage signals output from the respective voltage detecting units at the time of detection. If a voltage signal having a high/low division is present, it is considered that an abnormal branch is present. If the voltage signals are uniform and substantially correspond to a theoretical secondary voltage calculated from the primary current, the number of primary winding turns, and the number of secondary winding turns, then all three branches are considered normal. If the voltage signals are identical but significantly greater than the theoretical secondary voltage, then at least two branches are considered to be open.

The detecting accessory according to the present embodiment uses only one transformer and only one iron core, realizes a compact structure, facilitates miniaturization of the detecting accessory, and may be lower in cost than the structure of three transformers shown in fig. 4.

Fig. 4 shows a schematic diagram of a detection accessory and its detection system according to another embodiment of the utility model.

As shown in fig. 4, the detection accessory TC includes three transformers, namely, a first transformer IT1, a second transformer IT2, and a third transformer IT3. The first transformer IT1 includes a first core and a first primary winding and a first secondary winding SW1 arranged on the first core. The second transformer IT2 includes a second core and second primary and secondary windings SW2 arranged on the second core. The third transformer IT3 includes a third core and third primary and secondary windings SW3 arranged on the third core.

The detection accessory TC further comprises not shown voltage detection units for the three secondary windings respectively, connected in parallel with the corresponding secondary winding and for detecting the secondary voltage across the corresponding secondary winding.

The first secondary winding SW1, the second secondary winding SW2 and the third secondary winding SW3 are respectively connected in series with the first branch OK1, the second branch OK2 and the third branch OK3 of the star circuit of the three-phase motor and form a first loop, a second loop and a third loop accordingly.

Compared with the embodiment shown in fig. 3, the transformer for detecting the accessory TC according to the present embodiment is simpler in structure, lower in cost for parameter design and calculation, and easier in signal management.

It should be understood that the connection of each branch of the star circuit of the three-phase motor in series with the secondary winding in fig. 3 and 4 is merely illustrative, in this way, the state of each branch can be detected more conveniently and directly, however, the detection of the star circuit can be achieved by connecting the secondary winding in series with only two branches or with only one branch respectively.

A schematic illustration of a primary-side connection for the test attachment according to fig. 4 is shown next in fig. 5A, 5B. According to the embodiment of fig. 4, the detection accessory TC has three transformers and thus three primary windings.

As shown in fig. 5A, the first, second, and third primary windings PW1, PW2, and PW3 corresponding to the first, second, and third transformers IT1, IT2, and IT3 may be connected in series and supply a primary current through a common current supply unit CS.

Alternatively, as shown in fig. 5B, the first, second, and third primary windings PW1, PW2, and PW3 may be connected in series with the current supply unit CS, respectively, and supply a primary current through the current supply unit, respectively.

As shown in fig. 6, the detection accessory TC includes a transformer IT1 on which a secondary winding SW1 is arranged. Unlike the detection accessory shown in fig. 3 and 4, the detection accessory according to the present embodiment further includes a selection switch S connected in series with the secondary winding SW1. The secondary winding SW1 may be switchably connected to the first, second and third branches OK1, OK2 and OK3 via a selection switch S.

In the embodiment according to fig. 6, the secondary winding SW1 is connected at one end to the third contact switch CO3 of the star-closing contactor KAY, i.e. to the third branch OK3, and at the other end via the selection switch S optionally to the first contact switch CO1 or the second contact switch CO2 of the star-closing contactor KAY, i.e. optionally to the first branch OK1 or the second branch OK2, so that a third circuit comprising the first branch OK1 and the third branch OK3 is formed or a second circuit comprising the second branch OK2 and the third branch OK3 is formed.

Alternatively, the secondary winding SW1 is connected at one end to the first contact switch OA1 and at the other end to the second contact switch CO2 or the third contact switch CO3 via the selection switch S, or the secondary winding SW1 is connected at one end to the second contact switch OA2 and at the other end to the first contact switch CO1 or the third contact switch CO3 via the selection switch S.

Alternatively, the two-stage winding SW1 is connected in series with a first selector switch and a second selector switch at both ends, respectively, so as to be selectively connected with two of the contact switches or alternatively connected with two of the three branches of the star-circuit, respectively, so as to form a loop for detection.

According to an embodiment of the utility model, the detection system may further comprise a control module for controlling the on or off of the contact switch of the star-sealed contactor, thereby switching on or off the corresponding loop for detection. Accordingly, the detection accessory may also have a communication module for transmitting the detected secondary voltage signal to the control module or to a further determination module, so that the detection of the three-phase motor star circuit may be implemented on the basis of the secondary voltage signal.

It will be appreciated that upon detection, the star-sealed circuit may be deemed abnormal in the event that an abnormality in one of the circuits is detected, in order to notify the inspector and for subsequent repair. Thus, according to embodiments of the present utility model, detection may also be performed by forming one loop or two loops, respectively, with the detection accessory. By the detection accessory and the detection system, the abnormal state of the star sealing circuit can be detected, and the abnormal occurrence of the branch can be further detected, so that the time cost and the capital cost of the later maintenance are reduced.

In addition, according to the embodiment of the utility model, the detection is realized by means of the relation between the secondary voltage signal and the branch state shown in the table 1, and the absolute magnitude of the secondary voltage signal or the absolute proportional relation with the primary side signal is not needed, so that the implementation easiness and the reliability of the detection process are improved. Likewise, since the detection is achieved based on the degree of discrimination of the secondary voltage signal, the primary and secondary windings of the detection accessory can use smaller windings, for example with less than 100 turns, less than 30 turns, preferably less than 10 turns, which facilitates the miniaturization of the detection accessory, while reducing the potential risk of influencing the secondary side components and improving the safety of the detection process due to the limited current induced by the smaller windings. Meanwhile, with the detection accessory and the detection system according to the embodiment of the present utility model, it is possible to detect a star seal circuit including a star seal contactor and a motor winding, not only a circuit therebetween.

Advantageously, the detection accessory according to the embodiment of the utility model can be used as an accessory of the star-sealing contactor without changing the original star circuit structure, and can be realized in an integrated and miniaturized manner, so that a detection system can be formed through post-assembly, the detection process of the star-sealing circuit of the three-phase motor is simplified, and the time cost, the capital cost and the labor cost of the detection process are effectively reduced.

In general, the various example embodiments of the utility model may be implemented in hardware or special purpose circuits, software, firmware, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While aspects of the embodiments of the utility model are illustrated or described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The exemplary embodiments of the utility model described in detail above are illustrative only and are not limiting. It will be appreciated by those skilled in the art that various modifications and combinations of the embodiments or features thereof can be made without departing from the principles and spirit of the utility model, and such modifications are intended to be within the scope of the utility model.

Claims

1. A detection accessory for a three-phase motor star-sealing circuit, the detection accessory comprising:

a first transformer including a first core and a first primary winding and a first secondary winding disposed on the first core;

a current supply unit connected in series with the first primary winding for supplying a primary current to the first primary winding;

the first voltage detection unit is connected with the first secondary winding in parallel and is used for detecting first secondary voltages at two ends of the first secondary winding;

the first secondary winding is used for being connected in series with a first branch of the three-phase motor star sealing circuit.

2. The detecting accessory of claim 1, wherein the detecting accessory is configured to detect,

the first transformer further includes a second secondary winding and a third secondary winding disposed on the first core; and is also provided with

The detection accessory further includes:

the second voltage detection unit is connected with the second secondary winding in parallel and is used for detecting second secondary voltages at two ends of the second secondary winding;

the third voltage detection unit is connected with the third secondary winding in parallel and is used for detecting the third secondary voltage at two ends of the third secondary winding;

wherein the second secondary winding is used for being connected in series with a second branch of the three-phase motor star circuit, and

and the third secondary winding is used for being connected with a third branch of the star sealing circuit of the three-phase motor in series.

3. The detection accessory of claim 1, wherein the detection accessory further comprises:

a second transformer including a second core and a second primary winding and a second secondary winding disposed on the second core;

a third transformer comprising a third iron core and a third primary winding and a third secondary winding arranged on the third iron core;

4. The detecting accessory of claim 3, wherein the detecting accessory is configured to,

the first primary winding, the second primary winding, the third primary winding, and the current supply unit are connected in series.

5. The detecting accessory of claim 3, wherein the detecting accessory is configured to,

the first primary winding, the second primary winding and the third primary winding are respectively connected in series with the current supply unit.

6. The detection accessory of claim 1, wherein the detection accessory further comprises:

a selection switch, a first end of the selection switch is connected with a first end of the first secondary winding,

the second end of the first secondary winding is connected with the first branch, and the second end of the selection switch is switchably connected with the second branch and the third branch of the three-phase motor star sealing circuit.

7. The detection accessory of claim 1, wherein the detection accessory further comprises:

a first selection switch and a second selection switch, wherein the first end of the first selection switch is connected with the first end of the first secondary winding, the first end of the second selection switch is connected with the second end of the first secondary winding,

the second end of the first selection switch and the second end of the second selection switch are switchably connected with different branches of the three-phase motor star-sealing circuit respectively.

8. The detecting accessory according to any one of the preceding claims, wherein,

the number of turns of the primary winding and the secondary winding is less than 10 turns.

9. A detection system for a three-phase motor star-circuit, the detection system comprising:

the star circuit is sealed to three-phase motor includes: three branches, each branch comprises a motor winding and a contact switch for the corresponding branch in a star-sealing contactor which are connected in series;

the detection accessory of any one of claims 1-8, for detecting the three-phase motor star circuit.

10. The detection system of claim 9, wherein the detection system further comprises:

and the control module is used for controlling the on/off of a contact switch of the star-sealing contactor and realizing the detection of the star-sealing circuit of the three-phase motor based on the secondary voltage signal output by the detection accessory.