CN105634337A - Current setting-based AC motor decompression starting device and method - Google Patents

Abstract

The present invention provides a decompression starting device for an AC motor based on current setting, which is mainly composed of a current transformer, three decimal BCD dial switches and a controller; wherein, a power line for supplying power to the AC motor passes through the The primary winding of the current transformer, the output terminal of the secondary winding of the current transformer is connected to the current detection port of the controller; the three decimal BCD dial switches are respectively connected to the corresponding current setting port of the controller, and the To set the current when the Y-Δ of the AC motor starts; the output port of the controller is connected to the Y-Δ conversion circuit of the AC motor, and the external start/stop signal of the AC motor is input to the control corresponding input port of the device. The present invention also provides a method for the decompression starting device of the AC motor based on the current setting, so that the decompression starting process of the AC motor is stable and has no impact, and the starting safety of the motor is ensured.

Description

Device and method for decompression starting of AC motor based on current setting

technical field

The invention belongs to the technical field of alternating current motors, and in particular relates to an alternating current motor decompression starting device and method based on current setting, which are used for the decompression and stable start of small and medium power alternating current motors.

Background technique

AC asynchronous motors are widely used in various fields of industrial and agricultural production. At present, there are many starting methods for AC motors, and high-power AC motors usually use methods such as soft starters, rotor series resistors, and rotor series frequency sensitive reactors. Most of the starting of small and medium motors adopts Y-Δ decompression starting, stator series reactance and other methods.

The traditional Y-Δ decompression start uses a timing method to convert the Y (star) and Δ (delta) connection of the motor stator winding. Due to the different loads carried by the motor, the time required for starting varies. If the motor is started when the load is large, the traditional timing Y-Δ start will cause the motor to perform Y-Δ conversion under a large current. It will cause a large impact on the load, shorten the service life of the motor, and burn the motor in severe cases, failing to achieve the smooth effect of decompression starting.

Contents of the invention

The technical problem to be solved by the present invention is to provide an AC motor decompression starting device and method based on current setting, which can realize the stable conversion of the stator winding Y connection to the Δ connection during the Y-Δ start process, and at the same time ensure the motor's Start safe.

In order to solve the above-mentioned technical problems, the present invention provides a decompression starting device for an AC motor based on current setting, which is mainly composed of a current transformer, three decimal BCD dial switches and a controller; one of them supplies power to the AC motor The power line passes through the primary winding of the current transformer, and the output terminal of the secondary winding of the current transformer is connected to the current detection port of the controller; three decimal BCD dial switches are respectively connected to the corresponding The current setting port is used to set the current when the Y-Δ of the AC motor is started; the output port of the controller is connected to the Y-Δ conversion circuit of the AC motor, and the external start/stop of the AC motor The signals are input to corresponding input ports of the controller.

Further, the output end of the secondary winding of the current transformer is sequentially connected to a single-phase bridge rectifier circuit, a filter circuit, a potential regulator and an analog-to-digital conversion circuit, and then connected to the current detection port of the controller.

Further, the current transformer is fixed on the installation beam of the AC motor through screws and a mounting bracket.

Further, the controller is an AT89C52 series microcontroller controller.

Further, each BCD DIP switch has 5 pins: 8, 4, 2, 1 and A, A is the common terminal, connected to +5V power supply, when the number on the BCD DIP switch changes from 0 to 9, 8 , 4, 2, 1 pins will output the corresponding level.

Further, the Y-Δ conversion circuit is mainly composed of two relays K1 and K2, the coils of the relays K1 and K2 are respectively connected to the corresponding output ports of the controller, and the external start/stop signals of the AC motor are respectively passed through the contacts The contacts of the contacts KM1 and KM2 are input to the input ports of the controller, and when the contacts of the contactor KM1 are closed, the input port of the controller connected to the contacts is at a high level, and the controller connected to the coil of the relay K1 The output port of the relay is high level, the relay K1 is charged, and the auxiliary contact of the relay K1 controls the stator winding of the AC motor to connect into a Y shape to start; when the starting current of the AC motor reaches the value set by the three decimal BCD dial switches When the current is flowing, the output port of the controller connected to the relay K1 coil outputs low level, the relay K1 loses power, the output port of the controller connected to the relay K2 coil outputs high level, the relay K2 is charged, and the auxiliary contact of relay K2 controls the AC The stator winding of the motor is converted from a Y-shaped connection to a Δ-shaped connection, and the start is over; when the contact of the contactor KM2 is closed, the input port of the controller connected to the contact is high, and the controller connected to the relay K2 coil The output port outputs a low level, the relay K2 loses power, and the AC motor stops running.

Further, the Y-Δ conversion circuit also includes an indicator light, the indicator light is connected to the indicator light control port of the controller, and when the stator winding of the AC motor is connected to start in a Y shape, the indicator light The lamp control port outputs a high level, and the indicator lamp is charged to indicate; when the stator winding of the AC motor changes from a Y-shaped connection to a delta-shaped connection, the lamp control port outputs a low level, and the indicator lamp goes out when the power is off.

The present invention provides a method for the above-mentioned AC motor decompression starting device based on current setting, including:

Receive the external start signal of the AC motor through the corresponding input port of the controller;

Detecting the starting current of the stator during the starting process of the AC motor through a current transformer, and setting the current when the Y-Δ of the AC motor starts through three decimal BCD dial switches;

The controller controls the Y-Δ starting conversion of the AC motor according to the current set by the three decimal BCD dial switches and the starting current detected by the current transformer, and at the beginning, the The stator windings of the AC motor are connected in a Y shape to start, and when the starting current of the AC motor reaches the set current, then the stator windings of the AC motor are controlled to be converted from a Y-shaped connection to a Δ-shaped connection, and the end Y-Δ starts.

Further, the Y-Δ conversion circuit is mainly composed of two relays K1 and K2. When the controller receives an external start signal, the contact of the contactor KM1 is closed, and the output port of the controller connected to the coil of the relay K1 is high level, the relay K1 is charged, the auxiliary contact of the relay K1 controls the stator winding of the AC motor to connect into a Y shape to start; when the starting current of the AC motor reaches the set current, the output of the controller connected to the coil of the relay K1 The port outputs low level, relay K1 loses power, the output port of the controller connected to the coil of relay K2 outputs high level, relay K2 is charged, and the auxiliary contact of relay K2 controls the stator winding of the AC motor to change from Y-shaped connection to Δ-shaped Connection, start and end.

Further, when the controller receives an external stop signal, the contact of the contactor KM2 is closed, the input port of the controller connected to the contact is high level, and the output port of the controller connected to the relay K2 coil outputs low level , the relay K2 loses power, and the AC motor stops running.

Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

1. The AC motor decompression starting device based on current setting of the present invention has a simple structure and low cost. Through the cooperation of a current transformer, a controller and three decimal BCD dial switches, the Y-Δ starting process of the AC motor is realized. The stable conversion of the stator winding from the Y connection to the Δ connection makes the motor start and run safely.

2. The method of the AC decompression starting device based on current setting of the present invention measures the starting current of the stator winding of the AC motor through a current transformer during the Y-Δ starting process, and when the starting current of the motor is close to three decimal BCD dials When the current set by the code switch, the controller sends out a Y-Δ conversion signal to convert the Y-connection at the start of the stator winding to the Δ-connection, ending the Y-Δ start, so that the decompression start process of the AC motor is stable and No impact, ensuring the safety of starting the motor.

Description of drawings

Fig. 1 is a schematic structural view of an AC decompression starting device based on current setting according to a specific embodiment of the present invention;

Fig. 2 is the installation schematic diagram of the current transformer in the AC decompression starting device of the specific embodiment of the present invention;

Fig. 3 is a circuit structure diagram of an AC decompression starting device based on current setting according to a specific embodiment of the present invention.

detailed description

A current setting-based AC decompression starting device and method of the present invention will be further described in detail below in conjunction with the accompanying drawings.

As shown in Fig. 1, the present invention provides a kind of AC motor decompression starting device based on current setting, mainly is made up of current transformer 20, three decimal BCD dial switches 26 and controller 25; Wherein, for AC motor 11 A power line of the power supply for power supply passes through the primary winding of the current transformer 20, and the output terminal of the secondary winding of the current transformer 20 is connected to the current detection port of the controller; three decimal BCD dial switches 26 Connect to the current setting ports corresponding to the controller 25 respectively, for setting the current when the Y-Δ of the AC motor 11 starts; the output port of the controller 25 is connected to the Y-Δ of the AC motor 11. Δ conversion circuit 12 , the external start/stop signal of the AC motor 11 is input to the corresponding input port of the controller 25 .

Please refer to Fig. 2 and Fig. 3, in this embodiment, in order to enable the current transformer 20 to accurately detect the line current when the AC motor 11 is running, and make the Y-Δ conversion circuit 12 convert according to the set current, press The following steps are implemented in detail:

1. As shown in accompanying drawing 2, pass the power line 100 through the primary winding of the current transformer 20, and the current transformer 20 passes through the installation frame 111 and is fixed on the installation beam 110 of the AC motor 11 with screws 112, and the current transformer 20 The secondary winding is the current value detected by it.

2. Please refer to Figure 1 and Figure 3, connect No. 3 and No. 4 terminals of the secondary winding side of the current transformer 20 to No. 1 and No. 2 terminals of the single-phase bridge rectifier circuit 21 respectively as shown in Fig. 3, single-phase Terminals 3 and 4 of the bridge rectifier circuit 21 are respectively connected to two terminals of the filter circuit 22 and two terminals of the potentiometer 23 in turn, and the output terminal of the potential regulator 23 is connected to the input terminal of the analog-to-digital conversion circuit 25 . In this embodiment, the filter circuit 22 is mainly composed of a filter capacitor C, the No. 3 and No. 4 terminals of the single-phase bridge rectifier circuit 21 are connected in parallel with the filter capacitor 22, and the potential regulator 23 is composed of a resistor R1, an adjustable rheostat RP, and a resistor R3 in sequence Formed in series, the analog-to-digital conversion circuit 25 is an ADC0804 analog-to-digital conversion chip, the adjustment terminal 5 of the adjustable rheostat RP of the potentiometer 23 is connected to the Vin (+) end of the ADC0804 analog-to-digital conversion chip, and the resistor R3 and the ADC0804 analog-to-digital conversion chip The Vin(-) terminal of the ADC0804 is connected to the ground and the power supply terminal VCC of the ADC0804 analog-to-digital conversion chip is connected to the +5V power supply. The rated value of the output current of the secondary winding side of the current transformer 20 is 0.1A, and the adjustable rheostat RP of the potential regulator 23 can be adjusted so that the current transformer 20 can be rectified through the bridge rectification of the single-phase bridge rectifier circuit 21, The DC voltage input to the analog-to-digital conversion circuit after filtering by the filter circuit 22 is 0-5V, and 5V corresponds to 1.2 times the rated current of the AC motor 11, that is, when the AC motor 11 is in the rated operating state, it corresponds to a DC voltage of 4.17V. That is, when the current at the secondary winding side of the current transformer 20 is 0.1A, the voltage at the No. 5 output terminal of the adjustable rheostat RP is 4.17V.

3. Please refer to Fig. 1 and Fig. 3, the controller 25 adopts the AT89C52 series single-chip controller, and the output ports of DB0-DB7 of the ADC0804 analog-to-digital conversion chip are connected to the P3.0-P3.7 ports of the AT89C52 series single-chip controller. Before starting the AC motor 11, manually set the Y-Δ starting conversion current of the AC motor through the three decimal BCD dial switches 26 in the accompanying drawing 3, usually the conversion current is set to about 80% of the rated current of the motor, three times Two BCD dial switches 1, 2, and 3 respectively indicate the ones-hundreds digit of the set current, and can set the current to the hundreds digit when the Y-Δ of the AC motor 11 starts, meeting the current needs of various small and medium AC motors . Three decimal BCD dial switches 26 are respectively connected with P0.0-P0.3, P0.4-P0.7 ports and P1.0-P1.3 ports of the AT89C52 series microcontroller controller. Each BCD DIP switch has 5 pins, they are 8, 4, 2, 1 and A respectively, A is the common terminal, connected to +5V power supply, when the number on the DIP switch changes from 0 to 9, the 8421 leads The pin will output the corresponding level, for example, when the BCD dial switch is set to 1, the 1 pin is connected to the common control terminal A; when it is set to 3, the 1 and 2 pins are connected to the common control terminal A, by The output of each BCD dial switch is 8421 yards.

4. The controller 25 controls the Y-Δ conversion circuit 12 for starting the AC motor 11 according to the current set by the three decimal BCD dial switches 26 and the actual starting current of the AC motor 11 detected by the current transformer 20 . Among them, the Y-Δ conversion circuit 12 is formed by two relays K1, K2 and indicator light H1, and the No. 2 ends of the coils of the relays K1 and K2 are respectively connected to the P2.5 and P2.6 ports of the AT89C52 series microcontroller controller, contact The No. 2 end of the contactor KM1 contact (corresponding to the external start control signal of the AC motor) and the No. 4 end of the contactor KM2 contact (corresponding to the external stop control signal of the AC motor) are respectively connected to P2 of the AT89C52 series microcontroller controller. 1 and P2.2 ports, the common terminal 1 of the external start/stop signal of the AC motor 11 is connected to the +5V power supply. The indicator light H1 used to indicate the Y-Δ starting process of the AC motor 11 is connected to the P2.4 port of the AT89C52 series microcontroller controller. Thus, when the controller 25 receives an external start signal, the contact of the contactor KM1 is closed, the P2.1 port of the controller 25 is at a high level, the P2.5 port outputs a high level, the relay K1 is charged, and its auxiliary The contact controls the stator winding of the AC motor 11 to connect into a Y shape to start, and at the same time, the P2.4 port outputs a high level, and the indicator light H1 is charged to indicate; when the starting current of the AC motor 11 reaches the current set by the BCD toggle switch 26 , the P2.5 port outputs a low level, the relay K1 loses power, the P2.6 port outputs a high level after a certain time delay (for example, 0.5 seconds), the relay K2 is charged, and its auxiliary contact controls the stator winding of the AC motor 11 Convert from Y-shape connection to Δ-shape connection. After start-up, the AC motor 11 runs in the Δ-shape connection mode, the P2.4 port outputs a low level, and the indicator light H1 is powered off; when the controller 25 receives an external stop signal , the contacts of the contactor KM2 are closed, the P2.2 port is high level, the P2.6 port outputs low level, the relay K2 loses power, and the AC motor 11 stops running.

It can be seen from the above that the AC motor decompression starting device based on the current setting of the present invention has a simple structure and low cost. Through the cooperation of the current transformer, the controller and three decimal BCD dial switches, the Y-Δ start of the AC motor can be realized. During the process, the stator winding is smoothly converted from the Y connection to the Δ connection, and the motor starts and runs safely.

Please refer to FIG. 1 to FIG. 3 , the present invention also provides a method for the above-mentioned AC motor decompression starting device based on current setting, including:

Receive the external starting signal of the AC motor 11 through the corresponding input port of the controller 25;

Detect the starting current of the stator during the starting process of the AC motor 11 through the current transformer 20, and set the current when the Y-Δ of the AC motor 11 starts through three decimal BCD dial switches 26;

The controller 25 controls the Y-Δ start conversion of the AC motor 11 according to the current set by the three decimal BCD dial switches 26 and the start current detected by the current transformer 20. When the stator windings of the AC motor 11 are connected into a Y shape to start, when the starting current of the AC motor 11 reaches the set current, then the stator windings of the AC motor 11 are controlled to be connected by a Y shape. Convert to delta joint, end Y-delta start.

Further, the Y-Δ conversion circuit is mainly composed of two relays K1 and K2. When the controller receives an external start signal, the contact of the contactor KM1 is closed, and the output port of the controller connected to the coil of the relay K1 is high level, the relay K1 is charged, the auxiliary contact of the relay K1 controls the stator winding of the AC motor to connect into a Y shape to start; when the starting current of the AC motor reaches the set current, the output of the controller connected to the coil of the relay K1 The port outputs low level, relay K1 loses power, the output port of the controller connected to the coil of relay K2 outputs high level, relay K2 is charged, and the auxiliary contact of relay K2 controls the stator winding of the AC motor to change from Y-shaped connection to Δ-shaped Connection, start and end.

Further, when the controller receives an external stop signal, the contact of the contactor KM2 is closed, the input port of the controller connected to the contact is high level, and the output port of the controller connected to the relay K2 coil outputs low level , the relay K2 loses power, and the AC motor stops running.

From the above, the method of the AC decompression starting device based on current setting of the present invention measures the starting current of the stator winding of the AC motor through the current transformer during the Y-Δ starting process, and when the starting current of the motor is close to three When the current is set by a decimal BCD dial switch, the controller will send out a Y-Δ conversion signal to convert the Y connection at the start of the stator winding to the Δ connection, and end the Y-Δ start, thereby decompressing the AC motor. The starting process is smooth and shock-free, ensuring the safety of the motor starting.

Claims (10)

1. A decompression starting device for an AC motor based on current setting, characterized in that it is mainly composed of a current transformer, three decimal BCD dial switches and a controller; wherein, a power cord for supplying power to the AC motor passes through Through the primary winding of the current transformer, the output terminal of the secondary winding of the current transformer is connected to the current detection port of the controller; the three decimal BCD dial switches are respectively connected to the corresponding current setting of the controller The port is used to set the current when the Y-Δ of the AC motor starts; the output port of the controller is connected to the Y-Δ conversion circuit of the AC motor, and the external start/stop signal of the AC motor is input to corresponding input port of the controller. 2. AC motor decompression starting device as claimed in claim 1, is characterized in that, the secondary winding output end of described current transformer is connected with single-phase bridge rectifier circuit, filter circuit, potential regulator and analog-to-digital conversion successively After the circuit, connect to the current sense port of the controller. 3. The AC motor decompression starting device according to claim 1, wherein the current transformer is fixed on the mounting beam of the AC motor through screws and a mounting bracket. 4. The AC motor decompression starting device according to claim 1, wherein the controller is an AT89C52 series single-chip controller. 5. The AC motor decompression starting device according to claim 1, characterized in that, each BCD dial switch has 5 pins: 8, 4, 2, 1 and A, and A is a common terminal connected to +5V Power supply, when the number on the BCD DIP switch changes from 0 to 9, the 8, 4, 2, 1 pins will output the corresponding level. 6. The AC motor decompression starting device according to claim 1, wherein the Y-Δ conversion circuit is mainly composed of two relays K1 and K2, and the coils of the relays K1 and K2 are respectively connected to the corresponding coils of the controller. The output port of the AC motor, the external start/stop signal of the AC motor is input to the input port of the controller through the contacts of the contactor KM1 and KM2 respectively, and when the contact of the contactor KM1 is closed, the contact connected The input port of the controller is at high level, the output port of the controller connected to the coil of relay K1 is at high level, the relay K1 is electrified, and the auxiliary contact of relay K1 controls the stator winding of the AC motor to connect into a Y shape to start; when the AC When the starting current of the motor reaches the current set by the three decimal BCD dial switches, the output port of the controller connected to the relay K1 coil outputs a low level, the relay K1 loses power, and the output port of the controller connected to the relay K2 coil The output is high level, the relay K2 is charged, the auxiliary contact of the relay K2 controls the stator winding of the AC motor to change from the Y-shaped connection to the Δ-shaped connection, and the start is completed; when the contact of the contactor KM2 is closed, the control of the contact connection The input port of the controller is at a high level, the output port of the controller connected to the coil of the relay K2 outputs a low level, the relay K2 loses power, and the AC motor stops running. 7. The AC motor decompression starting device according to claim 6, wherein the Y-Δ conversion circuit also includes an indicator light, the indicator light is connected to the indicator light control port of the controller, and when When the stator windings of the AC motor are connected in a Y shape to start, the control port of the indicator light outputs a high level, and the indicator light indicates that it is charged; when the stator windings of the AC motor are connected from a Y shape to a Δ shape connection, the The indicator light controls the port to output low level, and the indicator light goes out when the power is off. 8. A method for the AC motor decompression starting device based on current setting according to any one of claims 1 to 7, characterized in that, comprising: Receive the external start signal of the AC motor through the corresponding input port of the controller; Detecting the starting current of the stator during the starting process of the AC motor through a current transformer, and setting the current when the Y-Δ of the AC motor starts through three decimal BCD dial switches; The controller controls the Y-Δ starting conversion of the AC motor according to the current set by the three decimal BCD dial switches and the starting current detected by the current transformer, and at the beginning, the The stator windings of the AC motor are connected in a Y shape to start, and when the starting current of the AC motor reaches the set current, then the stator windings of the AC motor are controlled to be converted from a Y-shaped connection to a Δ-shaped connection, and the end Y-Δ starts. 9. The method according to claim 8, wherein the Y-Δ conversion circuit is mainly composed of two relays K1 and K2, when the controller receives an external start signal, the contact of the contactor KM1 is closed, The output port of the controller connected to the relay K1 coil is at high level, the relay K1 is charged, and the auxiliary contact of the relay K1 controls the stator winding of the AC motor to connect into a Y shape to start; when the starting current of the AC motor reaches the set When the current is flowing, the output port of the controller connected to the relay K1 coil outputs low level, the relay K1 loses power, the output port of the controller connected to the relay K2 coil outputs high level, the relay K2 is charged, and the auxiliary contact of relay K2 controls the AC The stator winding of the motor is converted from a Y-shaped connection to a Δ-shaped connection, and the start-up ends. 10. The method according to claim 9, characterized in that, when the controller receives an external stop signal, the contact of the contactor KM2 is closed, the input port of the controller connected by the contact is high, and the relay K2 The output port of the controller connected to the coil outputs a low level, the relay K2 loses power, and the AC motor stops running.