CN201435701Y - Star-delta automatic switching device - Google Patents

Abstract

The utility model relates to a star-delta automatic switching device, including a star-delta connection switching switch, and also including a power factor measurement control module connected to control the star-delta connection switching switch and used to measure the power factor of an AC motor. In this star-delta automatic switching device, when the motor is running, the weight of the load is detected by the PFC power factor measurement control module, and the output control thyristor zero-crossing switching module is further output to cooperate with the star-delta switching to perform star-delta arc-free conversion, which solves the problem that the star-delta conversion device cannot automatically switch when the motor is unloaded or lightly loaded, thereby wasting power, and at the same time solves the problem that the arc generated during the star-delta switching process causes the contactor to be easily damaged and cannot be frequently switched.

Description

A star-delta automatic switching device

technical field

The utility model relates to an AC motor, in particular to a star-delta automatic switching device.

Background technique

At present, the star-delta conversion device in the AC motor is mainly used for switching between the star connection method of the motor starting and the delta connection method after the motor is in normal operation. However, when the existing motor is empty or lightly loaded, the star-delta conversion device cannot Automatically measure the load status of the motor to realize star-delta switching, which also wastes a lot of power. At the same time, the arc generated during the star-delta switching process will easily damage the contactor, so it cannot be switched frequently.

Utility model content

The technical problem to be solved by the utility model is how to provide a star-delta automatic switching device, which can automatically switch according to the load status, and further avoid electric arcs during switching.

The technical problem of the utility model is solved in this way: construct a kind of star-delta automatic switching device, comprise star-delta connection switching switch, also comprise connection control described star-delta connection switching switch, be used for measuring the power factor measurement control module of AC motor power factor .

According to the switch device provided by the utility model, the star-delta connection switch is two three-pole switches.

According to the switching device provided by the utility model, the star-delta connection switching switch is a two-way three-pole selection switch.

According to the switching device provided by the utility model, the power factor measurement control module includes a power factor controller and a current transformer connected thereto and a voltage terminal, the voltage terminal is connected to any phase of the three-phase power supply of the AC motor, and the current Transformer with the same mutual inductance.

According to the switching device provided by the utility model, the main body of the switching device further includes a zero-crossing detection drive unit and a control switch sequentially connected to the power factor measurement control module. There are three control switches, each corresponding to a phase, Connect the AC motor at one end and the AC power supply at the other end.

According to the switching device provided by the utility model, the control switch is an anti-parallel one-way thyristor or a two-way thyristor.

The star-delta automatic switching device provided by the utility model, when the motor is running, the weight of the load is detected by the PFC (power factor measurement control) module, and the output controls the thyristor zero-crossing switching module, which cooperates with the star-delta control circuit module to perform star-delta No arc conversion, stable and reliable conversion. It solves the problem that when the existing motor is empty or lightly loaded, the star-delta switching device cannot automatically measure the load state of the motor, and performs star-delta switching, which wastes a lot of power. At the same time, it solves the problem of the arc generated during the star-delta switching process, which leads to contact The device is easily damaged and cannot be switched frequently.

Description of drawings

The utility model is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is a star-delta system connection diagram of a specific embodiment of the present invention;

Fig. 2 is a schematic diagram of the control circuit in the star-delta system shown in Fig. 1;

FIG. 3 is a schematic diagram of the connection of the PFC power factor controller in the star-delta system shown in FIG. 1 .

Detailed ways

At first, illustrate the structure of the specific embodiment of the present utility model:

As shown in Figures 1 and 2, the automatic switching device in the star-delta system of the present invention is composed of a PFC power factor measurement control module, a thyristor zero-crossing switching module and a star-delta control circuit module, wherein:

- The PFC power factor measurement control module, the thyristor zero-crossing switching module and the star-delta control circuit module are connected to each other.

- The PFC power factor measurement control module includes: a PFC power factor controller, a current transformer, a voltage terminal, a power switch SB1 and a DC relay KA1.

- The PFC power factor controller calculates the power factor based on the voltage and current at the input.

- The current transformer and the voltage terminal are connected to the input terminal of the PFC controller for measuring the current and voltage of any one phase of the three-phase electricity.

- One end of the power switch SB1 is connected to the power supply, and the other end is connected to the input end of the PFC power factor controller.

-The DC relay KA1, one end is connected to the power supply, and the other end is connected to the output end of the PFC power factor controller

- The thyristor zero-crossing switching module includes: 3 groups of anti-parallel unidirectional thyristors, zero-crossing detection drive circuit.

- The three groups of anti-parallel unidirectional thyristors are connected in series between the KM1 and KM2 contactors.

- The zero-crossing detection driving circuit, the input is connected to the output terminal of the PFC power factor controller, and the output is connected to the control terminals of three groups of anti-parallel unidirectional thyristors.

- The star-delta control circuit module includes: contactors KM3, KM2, and KM1, and switches SB1 and SB2.

- One end of the contactor KM3 is connected to KA1 (normally open), and the other end is connected to KM2. One end that contacts KM2 is connected to KA1 (normally closed), and the other end is connected to KM3. One end of the contactor KM1 is connected to the output ends of KM2 and KM3 after parallel connection, the other end is connected to the output of SB2, and the input ends of KA1 (normally open) and KA1 (normally closed).

- The contactor, KM3 in series with KA1 (normally open)

- The contactor, KM2 in series with KA1 (normally closed)

-The output of the contactor KM3 is connected to the output of KM3 and KM2, and the input is connected to the input of KA1 (normally open) and KA1 (normally closed)

- The SB2 (normally open) is connected in parallel with KM1 (normally open), the input end is connected to the output of SB1, and the output end is connected to the input of KM1.

- As for the SB1, the output end is connected to SB2, and the input end is connected to the power supply.

Second, explain the working principle of the specific embodiment of the present utility model:

The working principle of the switching device is:

When the motor is running with light load, the normally open switch of SB2 is closed, the main contactor KM1 is closed, the PFC power factor controller outputs an open signal to KA1, and the star contactor KM3 is closed. The delta contactor KM2 is disconnected, and the PFC power factor controller outputs an open signal to the thyristor zero-crossing detection drive circuit, and the three groups of anti-parallel unidirectional thyristors are turned on, and the motor runs in star shape.

When the motor is running under heavy load, the SB2 normally open switch is closed, the main contactor KM1 is closed, the PFC power factor controller outputs a closing signal to KA1, and the star contactor KM3 is opened. The delta contactor KM2 is closed, and the PFC power factor controller outputs an open signal to the thyristor zero-crossing detection drive circuit, and the three groups of anti-parallel unidirectional thyristors are turned on, and the motor operates in a triangle.

Finally, illustrate the key of the specific embodiment of the present utility model:

As shown in Figure 3, the PFC power factor controller continuously detects the input current and voltage. When converting the star-delta contactor, the three groups of anti-parallel unidirectional thyristors are in the cut-off state, and after the conversion of the star-delta contactor is completed, it will be turned on for 3 Group anti-parallel one-way thyristor.

-When the light load of the motor is detected, the disconnect signal is output to KA1, and then the open signal is output to the thyristor zero-crossing detection drive circuit, and the motor operates in star form.

-When the motor is detected to be overloaded, output the close signal to KA1, and then output the open signal to the thyristor zero-crossing detection drive circuit, and the motor runs in star shape.

- When the motor needs to stop working, press SB1, the power will be cut off and the motor will stop.

The above descriptions are only preferred embodiments of the present utility model, and all equivalent changes and modifications made according to the claims of the present utility model shall fall within the scope of the claims of the present utility model.

Claims (6)

1. A star-delta automatic switching device, comprising a star-delta connection switch, characterized in that it also includes a power factor measurement control module for connecting and controlling the star-delta connection switch and for measuring the power factor of an AC motor. 2. The switching device according to claim 1, characterized in that the star-delta connection switch is two three-pole switches. 3. The switching device according to claim 1, wherein the star-delta connection switching switch is a two-way three-pole selection switch. 4. The switching device according to claim 1, characterized in that the power factor measurement control module includes a power factor controller and its connected current transformer and voltage terminal, and the voltage terminal is connected to any one of the three-phase power supply of the AC motor connected, the current transformer with the same mutual inductance. 5. The switching device according to claim 1, wherein the main body of the switching device further includes a zero-crossing detection drive unit and a control switch sequentially connected to the power factor measurement control module, and the number of the control switches is three, Each corresponds to a phase, and one end is connected to the AC motor, and the other end is connected to the AC power supply. 6. The switching device according to claim 1, wherein the control switch is an anti-parallel one-way thyristor or a two-way thyristor.

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