A frequency converter protection circuit and a frequency converter

Abstract

The application relates to the field of frequency converters, and discloses a frequency converter protection circuit and a frequency converter. The frequency converter protection circuit is connected between a frequency converter and a power supply; a contactor KM1 is connected in series in a starting circuit; an input end of a fault reporting circuit is connected with a first terminal K1 of the frequency converter, and an output end of the fault reporting circuit is connected with a power supply N line; an input end of the starting circuit is connected with a second terminal K2 of the frequency converter, an output end of the starting circuit is connected with the power supply N line, and the starting circuit and the fault reporting circuit are connected in parallel; when the fault reporting circuit receives a fault signal, the first terminal K1 is closed, the second terminal K2 is disconnected, normally open contacts of the contactor KM1 are disconnected, and the frequency converter is stopped. According to the application, when a fault occurs, the normally open contacts of the contactor KM1 are disconnected, the connection between an external circuit and the frequency converter can be cut off, the fault voltage can be prevented from entering the frequency converter, and the internal elements of the frequency converter can be prevented from being damaged.

Description

Technical Field

[0001] This invention relates to the field of frequency converters, and particularly to a frequency converter protection circuit and a frequency converter. Background Technology

[0002] Frequency converters adjust the voltage and frequency of the output power supply by switching their internal IGBTs, providing the required power voltage according to the actual needs of the motor, thereby achieving energy saving and speed regulation. In addition, frequency converters have many protection functions, such as overcurrent, overvoltage, and overload protection. With the continuous improvement of industrial automation, frequency converters have been widely used.

[0003] However, in the process of implementing the present invention, it was found that at least the following problems exist in the prior art: when the frequency converter itself fails or other electrical components connected to the frequency converter fail, the fault voltage will still enter the frequency converter, causing damage to the internal components of the frequency converter. Summary of the Invention

[0004] In view of this, the present invention provides a frequency converter protection circuit and a frequency converter.

[0005] Specifically, the following technical solutions are included:

[0006] On the one hand, a frequency converter protection circuit is provided, connected between the frequency converter and the power supply.

[0007] This includes contactor KM1, the starting circuit, and the fault reporting circuit;

[0008] The contactor KM1 is connected in series in the starting circuit;

[0009] The input terminal of the fault reporting circuit is connected to the first terminal K1 of the frequency converter, and the output terminal of the fault reporting circuit is connected to the power supply line N.

[0010] The input terminal of the starting circuit is connected to the second terminal K2 of the frequency converter, the output terminal of the starting circuit is connected to the power supply line N, and the starting circuit and the fault reporting circuit are connected in parallel.

[0011] When the starting circuit receives a start signal, the first terminal K1 is disconnected, the second terminal K2 is closed, the normally open contact of the contactor KM1 is closed, and the frequency converter starts.

[0012] When the fault reporting circuit receives a fault signal, the first terminal K1 closes, the second terminal K2 opens, the normally open contact of the contactor KM1 opens, and the frequency converter stops.

[0013] Preferably, the startup circuit includes a pre-start module;

[0014] The first end of the second terminal K2 of the frequency converter is connected to the power supply line L, the second end of the second terminal K2 of the frequency converter is connected to the input terminal of the pre-start module, the output terminal of the pre-start module is connected to the power supply line N, and the second terminal K2 of the frequency converter, the first normally open contact of the contactor KM1 and the coil of the contactor KM1 are connected in series.

[0015] The pre-start module includes a first switch SA1;

[0016] The first normally open contact of the contactor KM1 and the first switch SA1 are connected in parallel to form a first self-locking circuit.

[0017] Preferably, the pre-start module includes a second switch SB1;

[0018] The second terminal K2 of the frequency converter, the first normally open contact of the contactor KM1, the second switch SB1, and the coil of the contactor KM1 are connected in series.

[0019] Preferably, the startup circuit includes a startup module;

[0020] The input terminal of the starting module is connected to the power supply line L, the output terminal of the starting module is connected to the power supply line N, and the second normally open contact of the contactor KM1 is connected in series in the starting module.

[0021] Preferably, the starting module includes a relay KA1 and a third switch SA2;

[0022] The first normally open contact of the relay KA1, the second normally open contact of the contactor KM1, and the coil of the relay KA1 are connected in series.

[0023] The first normally open contact of the relay KA1 and the third switch SA2 are connected in parallel to form a second self-locking circuit.

[0024] The frequency converter includes an internal starting module, the input and output terminals of which are respectively connected to two starting terminals of the frequency converter.

[0025] The second normally open contact of the relay KA1 is connected in series in the internal starting module.

[0026] Preferably, the start-up module further includes a fourth switch SB2;

[0027] The first normally open contact of the relay KA1, the fourth switch SB2, the second normally open contact of the contactor KM1, and the coil of the relay KA1 are connected in series.

[0028] Preferably, the fault reporting circuit includes a relay KA2;

[0029] The first terminal K1 of the frequency converter is connected to the power supply line L, the second terminal K1 of the frequency converter is connected to the input terminal of the fault reporting circuit, and the output terminal of the fault reporting circuit is connected to the power supply line N.

[0030] The second end of the first terminal K1 is connected in series with the coil of the relay KA2, which is used to report a fault indication to the DCS.

[0031] Preferably, the output terminal of the frequency converter is connected to the input terminal of the motor;

[0032] The third normally open contact of the contactor KM1 is connected in series in the connection circuit between the frequency converter and the motor.

[0033] On the other hand, a frequency converter is provided, to which the frequency converter protection circuit described above is connected.

[0034] Preferably, the frequency converter is connected to the motor;

[0035] The motor is connected to an electromagnetic braking device.

[0036] The electromagnetic braking device is connected to a power source via a rectifier.

[0037] The beneficial effects of the technical solution provided by this invention include at least the following:

[0038] This invention improves the safety of the frequency converter by setting up a contactor KM1, which disconnects all normally open contacts of the contactor KM1 when a fault occurs, thus cutting off the connection between the external circuit and the frequency converter and preventing fault voltage from entering the frequency converter and causing damage to the internal components of the frequency converter. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of the connection relationship of a frequency converter protection circuit provided in one embodiment of the present invention;

[0041] Figure 2 A schematic diagram of the connection relationship of a frequency converter protection circuit provided in another embodiment of the present invention.

[0042] The reference numerals in the figure are respectively:

[0043] 1-Inverter; 2-Motor; 3-Pre-start module; 4-Start module; 5-Internal start circuit; 6-Fault reporting circuit.

[0044] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] To make the technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0047] In one embodiment, such as Figure 1 As shown, a frequency converter protection circuit is connected between the frequency converter 1 and the power supply. The frequency converter protection circuit includes a contactor KM1, a starting circuit, and a fault reporting circuit 6. The coil and normally open contact of contactor KM1 are connected in series in the starting circuit. The input terminal of the fault reporting circuit 6 is connected to the first terminal K1 of the frequency converter 1, and the output terminal of the fault reporting circuit 6 is connected to the power supply line N. The input terminal of the starting circuit is connected to the second terminal K2 of the frequency converter 1, and the output terminal of the starting circuit is connected to the power supply line N. The starting circuit and the fault reporting circuit 6 are connected in parallel. When the starting circuit receives a start signal, the first terminal K1 opens, the second terminal K2 closes, the normally open contact of contactor KM1 closes, and the frequency converter 1 starts. When the fault reporting circuit 6 receives a fault signal, the first terminal K1 closes, the second terminal K2 opens, the normally open contact of contactor KM1 opens, and the frequency converter 1 stops.

[0048] Specifically, when inverter 1 is in normal condition, the starting circuit receives a start signal, the first terminal K1 is opened, the second terminal K2 is closed, the coil of contactor KM1 is energized, the normally open contact of contactor KM1 is closed, the starting circuit is connected, and inverter 1 starts normally.

[0049] Furthermore, the inverter protection circuit also includes a fault detection circuit, which is connected to the fault reporting circuit 6. The fault detection circuit is used to report a fault signal to the fault reporting circuit 6. When the fault reporting circuit 6 receives the fault signal reported by the fault detection circuit, the first terminal K1 closes and the second terminal K2 opens. At this time, the coil of contactor KM1 is de-energized, the normally open contact of contactor KM1 opens, and the inverter 1 stops.

[0050] Since contactor KM1 is connected in series in the starting circuit, the normally open contact of contactor KM1 can disconnect the connection between the external circuit and inverter 1, preventing fault voltage from entering inverter 1 and causing damage to the internal components of inverter 1, thus improving the safety of inverter.

[0051] Furthermore, in one embodiment, such as Figure 1 As shown, the starting circuit includes a pre-start module 3. The first end of the second terminal K2 of the inverter 1 is connected to the power supply line L, and the second end of the second terminal K2 of the inverter 1 is connected to the input terminal of the pre-start module 3. The output terminal of the pre-start module 3 is connected to the power supply line N. The second terminal K2 of the inverter 1, the first normally open contact of contactor KM1, and the coil of contactor KM1 are connected in series. The pre-start module 3 includes a first switch SA1. The first normally open contact of contactor KM1 and the first switch SA1 are connected in parallel to form a first self-locking circuit.

[0052] Specifically, the second terminal K2 of inverter 1 is normally closed, while the first terminal K1 is normally open. When the first switch SA1 is pressed, the starting circuit receives a start signal, and current is generated between the power supply L line and the power supply N line. The current flows sequentially through the second terminal K2 of inverter 1, the first switch SA1, and the coil of contactor KM1. The coil of contactor KM1 is energized, and both the first and second normally open contacts of contactor KM1 close. At this time, inverter 1 is in the start-enabled state. The pre-start module 3 can send a start-enabled signal to the controller to prove that the starting circuit is normal and to check for defects in advance.

[0053] In another embodiment, such as Figure 1 As shown, the pre-start module 3 includes a second switch SB1. The second terminal K2 of the frequency converter 1, the first normally open contact of the contactor KM1, the second switch SB1, and the coil of the contactor KM1 are connected in series. The second switch SB1 is normally closed and can be manually opened to disconnect the frequency converter 1 from the power supply.

[0054] Furthermore, in other embodiments, such as Figure 1As shown, the starting circuit includes a starting module 4. The input terminal of the starting module 4 is connected to the power supply line L, and the output terminal of the starting module 4 is connected to the power supply line N. The second normally open contact of contactor KM1 is connected in series in the starting module 4. When the coil of contactor KM1 is de-energized, the second normally open contact of contactor KM1 can disconnect the starting module 4, thereby cutting off the connection between the frequency converter and the power supply.

[0055] In another embodiment, such as Figure 1 As shown, the starting module 4 includes a relay KA1 and a third switch SA2. The first normally open contact of relay KA1, the second normally open contact of contactor KM1, and the coil of relay KA1 are connected in series. The first normally open contact of relay KA1 and the third switch SA2 are connected in parallel to form a second self-locking circuit. The frequency converter 1 includes an internal starting module 5, whose input and output terminals are respectively connected to the two starting terminals of the frequency converter 1. The second normally open contact of relay KA1 is connected in series in the internal starting module 5.

[0056] Specifically, the linkage between the starting module 4 and the internal starting module 5 can be achieved through the setting of relay KA1. When the first switch SA1 is pressed, the starting circuit receives a start signal, and current is generated between the power supply L line and the power supply N line. The current flows sequentially through the second terminal K2 of inverter 1, the first switch SA1, and the coil of contactor KM1. The coil of contactor KM1 is energized, and both the first normally open contact and the second normally open contact of contactor KM1 are closed. At this time, inverter 1 is in the start-allowed state. Then, when the third switch SA2 is pressed, the coil of relay KA1 is energized, and both the first normally open contact of relay KA1 and the second normally open contact of contactor KM1 are closed, and inverter 1 starts.

[0057] In another embodiment, such as Figure 1 As shown, the starting module 4 also includes a fourth switch SB2. The first normally open contact of relay KA1, the fourth switch SB2, the second normally open contact of contactor KM1, and the coil of relay KA1 are connected in series.

[0058] Specifically, the fourth switch SB2 is normally closed. It can be manually disconnected to break the connection between the inverter 1 and the power supply.

[0059] In another embodiment, such as Figure 1 As shown, the fault reporting circuit 6 includes a relay KA2. The first terminal of the inverter 1's first terminal K1 is connected to the power supply line L, the second terminal of the inverter 1's first terminal K1 is connected to the input terminal of the fault reporting circuit 6, and the output terminal of the fault reporting circuit 6 is connected to the power supply line N. The second terminal of the first terminal K1 is connected in series with the coil of the relay KA2, which is used to report a fault indication to the DCS.

[0060] Specifically, when the fault reporting circuit 6 receives a fault signal, the first terminal K1 closes, the coil of the relay KA2 is energized, and a fault indication signal is sent to the DCS; at this time, the second terminal K2 opens, the coil of the contactor KM1 is de-energized, and both the first normally open contact and the second normally open contact of the contactor KM1 open, cutting off the connection between the inverter 1 and the power supply.

[0061] In other embodiments, such as Figure 1 As shown, the output terminal of inverter 1 is connected to the input terminal of motor 2. The third normally open contact of contactor KM1 is connected in series in the connection circuit between inverter 1 and motor 2.

[0062] Specifically, when the first switch SA1 is pressed, the starting circuit receives a start signal, generating current between the power supply L line and the power supply N line. This current flows sequentially through the second terminal K2 of inverter 1, the first switch SA1, and the coil of contactor KM1. The coil of contactor KM1 is energized, and the first, second, and third normally open contacts of contactor KM1 all close, putting inverter 1 in a start-enabled state. Next, when the third switch SA2 is pressed, the coil of relay KA1 is energized, and the first and second normally open contacts of relay KA1 and contactor KM1 close, starting inverter 1 and enabling motor 2 to rotate. When the fault reporting circuit 6 receives a fault signal, the first terminal K1 closes, the coil of relay KA2 is energized, and a fault indication signal is sent to the DCS. At this time, the second terminal K2 is disconnected, the coil of contactor KM1 is de-energized, and the first normally open contact, the second normally open contact, and the third normally open contact of contactor KM1 are all disconnected, cutting off the connection between inverter 1 and the power supply, and simultaneously cutting off the connection between inverter 1 and motor 2.

[0063] This embodiment also introduces a frequency converter 1, to which the aforementioned frequency converter protection circuit is connected. The circuit structure and principle of the frequency converter protection circuit can be found in the above embodiments, and will not be repeated here.

[0064] Specifically, inverter 1 is connected to motor 2. Motor 2 is connected to an electromagnetic braking device. For example... Figure 2 As shown, the electromagnetic braking device is connected to the power supply via a rectifier.

[0065] The rectifier is a half-wave rectifier, and the electromagnetic brake is a DC brake. The input of the half-wave rectifier is connected to a single-phase 380V power supply, and the output of the half-wave rectifier is connected to a 170V DC brake.

[0066] Specifically, a braking resistor R is connected to the internal terminals P and DB of the frequency converter.

[0067] Specifically, when the motor 2 driven by inverter 1 goes from high speed to low speed (zero speed), the electrical frequency changes rapidly. However, the rotor of motor 2, carrying a load, has a large mechanical inertia and cannot stop quickly. As a result, motor 2 generates a back electromotive force EU (terminal voltage). The reverse voltage torque generated is opposite to the original voltage torque of motor 2, giving motor 2 a strong braking torque and forcing the rotor to stop quickly. However, since inverter 1 is usually an AC-DC-AC main power AC / DC rectifier circuit, it is irreversible and cannot be fed back to the grid. As a result, the voltage across the capacitor in the main circuit increases, and the boosted voltage may break down the power electronic switching devices.

[0068] The internal braking resistor R of inverter 1 is connected between internal terminal P and internal DB to help motor 2 convert the regenerative electrical energy generated by rapid stopping into heat energy. However, for applications requiring large inertia mechanical loads or potential energy loads that need to maintain braking after power failure, an electromagnetic braking device is required.

[0069] Specifically, the electromagnetic braking device is installed on motor 2 and consists of a moving iron core, a stationary iron core, and friction components. The stationary iron core is fixed to a stationary support of motor 2. Inside the stationary iron core is an electromagnetic coil. When energized, the coil generates electromagnetic force, which overcomes the spring force and attracts the moving iron core. The moving iron core then disengages from the friction components, preventing frictional torque and allowing the shaft of motor 2 to rotate freely. Conversely, when the stationary iron core coil is de-energized, the electromagnetic force disappears, and the moving iron core springs back under the spring force, applying positive pressure to the friction surface and generating frictional torque in the friction components, thus overcoming axial inertia and stopping the rotation. Preferably, the power supply for the electromagnetic braking device should be a mains frequency AC power supply; variable frequency power supplies are strictly prohibited from powering the braking device.

[0070] In this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "a plurality" refers to two or more unless otherwise expressly defined.

[0071] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. The invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only.

[0072] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A frequency converter protection circuit, connected between the frequency converter and the power supply, characterized in that, This includes contactor KM1, starting circuit, and fault reporting circuit; The contactor KM1 is connected in series in the starting circuit; The input terminal of the fault reporting circuit is connected to the first terminal K1 of the frequency converter, and the output terminal of the fault reporting circuit is connected to the power supply line N. The input terminal of the starting circuit is connected to the second terminal K2 of the frequency converter, the output terminal of the starting circuit is connected to the power supply line N, and the starting circuit and the fault reporting circuit are connected in parallel. When the starting circuit receives a start signal, the first terminal K1 is disconnected, the second terminal K2 is closed, the normally open contact of the contactor KM1 is closed, and the frequency converter starts. When the fault reporting circuit receives a fault signal, the first terminal K1 closes, the second terminal K2 opens, the normally open contact of the contactor KM1 opens, and the frequency converter stops. The startup circuit includes a pre-start module; The first end of the second terminal K2 of the frequency converter is connected to the power supply line L, the second end of the second terminal K2 of the frequency converter is connected to the input terminal of the pre-start module, the output terminal of the pre-start module is connected to the power supply line N, the second terminal K2 of the frequency converter, the first normally open contact of the contactor KM1 and the coil of the contactor KM1 are connected in series, and the second end of the coil of the contactor KM1 serves as the output terminal of the pre-start module. The pre-start module includes a first switch SA1; The first normally open contact of the contactor KM1 and the first switch SA1 are connected in parallel to form a first self-locking circuit. The startup circuit includes a startup module; The input terminal of the starting module is connected to the power supply line L, the output terminal of the starting module is connected to the power supply line N, and the second normally open contact of the contactor KM1 is connected in series in the starting module. The output terminal of the frequency converter is connected to the input terminal of the motor; The third normally open contact of the contactor KM1 is connected in series in the connection circuit between the frequency converter and the motor.

2. The inverter protection circuit according to claim 1, characterized in that, The pre-start module also includes a second switch SB1; The second terminal K2 of the frequency converter, the first normally open contact of the contactor KM1, the second switch SB1, and the coil of the contactor KM1 are connected in series.

3. The inverter protection circuit according to claim 1, characterized in that, The start-up module also includes a relay KA1 and a third switch SA2; The first normally open contact of the relay KA1, the second normally open contact of the contactor KM1, and the coil of the relay KA1 are connected in series, and the second end of the coil of the relay KA1 serves as the output terminal of the starting circuit. The first normally open contact of the relay KA1 and the third switch SA2 are connected in parallel to form a second self-locking circuit. The frequency converter also includes an internal starting module, the input and output terminals of which are respectively connected to the two starting terminals of the frequency converter; The second normally open contact of the relay KA1 is connected in series in the internal starting module.

4. The inverter protection circuit according to claim 3, characterized in that, The startup module also includes a fourth switch SB2; The first normally open contact of the relay KA1, the fourth switch SB2, the second normally open contact of the contactor KM1, and the coil of the relay KA1 are connected in series.

5. The inverter protection circuit according to claim 1, characterized in that, The fault reporting circuit also includes a relay KA2; The first terminal K1 of the frequency converter is connected to the power supply line L, the second terminal K1 of the frequency converter is connected to the input terminal of the fault reporting circuit, and the output terminal of the fault reporting circuit is connected to the power supply line N. The second end of the first terminal K1 is connected in series with the coil of the relay KA2. The second end of the coil of the relay KA2 serves as the output terminal of the fault reporting circuit. The relay KA2 is used to report a fault indication to the DCS.

6. A frequency converter, characterized in that, It is connected to the inverter protection circuit as described in any one of claims 1-5.

7. The frequency converter according to claim 6, characterized in that, The frequency converter is connected to the motor; The motor is connected to an electromagnetic braking device. The electromagnetic braking device is connected to a power source via a rectifier.

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