CN218243013U - Circuit protector and frequency conversion circuit - Google Patents

Abstract

The utility model discloses a circuit protector and a frequency conversion circuit, which are used for being connected with a combined linked switch in parallel and comprise a plurality of protection modules; wherein the protection module comprises a first harmonic circuit and a second harmonic circuit; the first harmonic circuit is connected in parallel with the second harmonic circuit; the first harmonic circuit is used for draining a first harmonic current entering the combined gang switch; the second harmonic circuit is used for draining second harmonic current entering the combined gang switch; the first harmonic current is a harmonic current which is several times of the frequency of the fundamental current and the frequency of which is less than or equal to 1 KHz; the second harmonic current is a harmonic current with the frequency greater than 1 KHz; the circuit protector can reduce the potential safety hazards of personnel, equipment and the environment when the frequency conversion system has power frequency leakage faults. The utility model discloses but wide application is in the protection circuit technical field.

Description

Circuit protector and frequency conversion circuit

Technical Field

The utility model belongs to the technical field of the protection circuit technique and specifically relates to a circuit protector.

Background

In the prior art, in order to ensure personal and equipment safety, a linkage combination switch consisting of an AC type residual current protector and a main circuit breaker is arranged on the input side of a frequency converter, but the frequency converter generates low-order and high-frequency harmonic waves during operation, and the harmonic waves have smaller amplitude to the action current of the AC type residual current protector, so that misoperation of the linkage combination switch is easily caused, and the stability of frequency conversion equipment and a system is seriously influenced. If the linkage combination switch is not installed and the equipment is well grounded, harmonic leakage current has little influence on people (people are equivalent to the electrical potential), and electromagnetic interference is generated on the equipment, so that the requirement can be met from the design aspect of system equipment, but potential safety hazards such as electric shock of personnel, damage of the equipment, fire of the environment and the like exist when power frequency leakage current accidents are caused by insulation damage.

SUMMERY OF THE UTILITY MODEL

The utility model aims to solve one of the technical problems existing in the correlation technique to a certain extent at least.

Therefore, an object of the embodiment of the utility model is to provide a circuit protector, this circuit protector can reduce the potential safety hazard of personnel, equipment and environment when frequency conversion system takes place power frequency electric leakage trouble.

In order to achieve the technical purpose, the embodiment of the present invention adopts a technical solution including:

a circuit protector is used for being connected with a combined linked switch in parallel and comprises a plurality of protection modules; wherein the protection module comprises a first harmonic circuit and a second harmonic circuit; the first harmonic circuit is connected in parallel with the second harmonic circuit; the first harmonic circuit is used for draining a first harmonic current entering the combined gang switch; the second harmonic circuit is used for draining second harmonic current entering the combined gang switch; the first harmonic current is a harmonic current which is several times of the frequency of the fundamental current and the frequency of which is less than or equal to 1 KHz; the second harmonic current is a harmonic current with frequency greater than 1 KHz.

In addition, according to the present invention, the circuit protector according to the above embodiment may further have the following additional technical features:

optionally, in an embodiment of the present invention, the first harmonic circuit includes a first harmonic branch, a second harmonic branch, and a third harmonic branch; the first harmonic branch, the second harmonic branch and the third harmonic branch are connected in parallel.

Optionally, in an embodiment of the present invention, the second harmonic circuit includes a high frequency capacitor; the capacitive reactance of the high-frequency capacitor to the 50Hz fundamental wave is 158-160 omega.

Optionally, in an embodiment of the present invention, the first harmonic branch includes a first inductor and a first capacitor; the first inductor is connected with the first capacitor in series; the resonance frequency of the first harmonic branch is 250Hz.

Optionally, in an embodiment of the present invention, the second harmonic branch includes a second inductor and a second capacitor; the second inductor is connected with the second capacitor in series; the resonant frequency of the first harmonic branch is 350Hz.

Optionally, in an embodiment of the present invention, the third harmonic branch includes a third inductor and a third capacitor; the third inductor is connected with the third capacitor in series; the resonant frequency of the third harmonic branch is 450Hz.

Optionally, in an embodiment of the present invention, a capacitance value of the first capacitor is 5uF to 15uF.

Optionally, in an embodiment of the present invention, a capacitance value of the second capacitor is 5uF to 15uF.

Optionally, in an embodiment of the present invention, a capacitance value of the third capacitor is 5uF to 15uF.

Furthermore, the utility model also provides a frequency conversion circuit, including at least one as above-mentioned arbitrary embodiment a circuit protector.

Advantages and benefits of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention:

the embodiment of the utility model provides an in the embodiment, circuit protector sets up between multiphase power and converter, parallelly connected first harmonic circuit of every phase cable output and the second harmonic circuit of multiphase power, with mutual-inductive secondary side winding "parallelly connected reposition of redundant personnel" of the residual current protection device in the combination gang switch, coupling to the low order harmonic and the high frequency carrier wave of linkage gang switch that can significantly reduce, and then the high frequency leakage current that produces among the reduction frequency conversion system leads to the problem of earth leakage protection switch malfunction, personnel when also can reduce frequency conversion system and take place power frequency electric leakage trouble, the potential safety hazard of equipment and environment.

Drawings

Fig. 1 is a schematic diagram of a circuit structure of a frequency conversion system according to the present invention;

fig. 2 is a schematic diagram of a position of a circuit protector according to the present invention;

fig. 3 is a schematic structural diagram of a protection module of a circuit protector according to the present invention;

fig. 4 is a schematic structural diagram of a first harmonic circuit of a circuit protector according to the present invention;

fig. 5 is an equivalent circuit diagram of a frequency conversion circuit before and after the application circuit protector of the present invention.

Detailed Description

Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary only for the purpose of explaining the present invention, and should not be construed as limiting the present invention.

In the description of the present invention, it is to be understood that the terms "distance", "upper", "lower", "left", "right", "front", "rear", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Referring to fig. 1, in the field of application of the conventional frequency converter, in order to prevent the occurrence of the conditions such as input power supply abnormality, personal electric shock, equipment failure and even fire caused by the insulation breakdown of a frequency conversion system, an AC type residual current protector and a main circuit breaker linkage combination switch are generally installed between a multiphase input power supply and the frequency converter, and the main purpose is to cut off a power supply circuit and protect the safety of personnel and equipment by linkage of a residual current flowing through a protection device and a main circuit breaker when electric leakage occurs. The installation and application of the linkage combination switch in the frequency converter are shown in figure 1, taking a three-phase power supply as an example, the linkage combination switch consists of a protection device and a main circuit breaker, the A, B and C three-phase outputs of a three-phase power frequency input power supply AC380 are respectively connected with the input ends 1,3 and 5 of a residual current protection device, the output ends 2,4 and 6 of the residual current protection device are respectively connected with the input ends 1,3 and 5 of the main circuit breaker, and the output ends 2,4 and 6 of the main circuit breaker are respectively connected with the input ends a, B and C of the frequency converter.

However, after a linkage combination switch composed of an AC type residual current protector and a main circuit breaker is installed at the input end of the existing frequency converter, a trip phenomenon frequently occurs, and continuous and stable operation of equipment is seriously affected. Aiming at the problem of frequent tripping of a residual current protector of a frequency conversion system, a great deal of existing research finds that considerable earth leakage current can be generated when the frequency converter operates, the frequency converter adopts PWM modulation to enable frequency conversion output voltage to be modulation wave, the characteristic voltage contains a great deal of harmonic waves, the harmonic waves can generate earth leakage current through a parasitic capacitor of a motor winding and an output cable wire to the ground, and leakage current is coupled to a three-phase power supply through a ground system to cause linkage combined switching action.

However, the existing tests and researches find that the leakage current at the input side of the frequency conversion system mainly comprises three parts, namely 50Hz fundamental wave, low-order harmonics of 3 (150 Hz), 5 (250 Hz), 7 (350 Hz), 9 (450 Hz) and the like, carrier waves (1 k-20 k) and high-frequency harmonics of multiples thereof, wherein the 50Hz fundamental wave represents the characteristics of an input power supply, the low-order harmonics are generated by a rectification link, and the high-frequency harmonics are generated by PWM carrier modulation. Further research shows that when the number of frequency converters which operate simultaneously in a system is larger, the leakage current is larger, and the high-frequency harmonic content exceeds the fundamental content.

The typical AC type residual current protection device is disassembled and analyzed, and the action of the residual current protection device depends on the current average value rectified by the mutual inductance secondary side alternating current, the mutual inductance secondary side current enters a rectifier after passing through a 2.2uF capacitor, and the capacitive reactance formula 1/(2x3.1416xfxC) shows that the capacitive reactance of the capacitor to low-frequency current is large, and the capacitive reactance to high-frequency current is small, so that the action amplitude of fundamental current is large, and the action amplitude of harmonic current is small.

In order to ensure the safety of human bodies and equipment, an AC type residual current protector and a main circuit breaker linkage combined switch are installed on the input side of the frequency converter, but low-order and high-frequency harmonic waves are generated when the frequency converter operates, and the amplitude of the harmonic waves to the action current of an AC type residual current protection device is smaller, so that misoperation of the linkage combined switch is easily caused, and the stability of frequency conversion equipment and a system is seriously influenced. If the linkage combination switch is not installed and the equipment is well grounded, harmonic leakage current has little influence on people (people are the same electric potential), electromagnetic interference is generated on the equipment, the requirement can be made on the design level of system equipment, but when the power frequency leakage current accident is caused by insulation damage, potential safety hazards such as electric shock of personnel, equipment damage and environmental fire can exist.

Accordingly, embodiments of the present application provide a circuit protector that can substantially reduce low order harmonics and high frequency carriers coupled to a ganged combination switch; referring to fig. 2, in fig. 2, the circuit protector 1 is disposed between the output end of the multiphase power supply and the combined gang switch, and may include a plurality of protection modules 11; in the present application, the number of protection modules 11 may be 1, two, or more than two, and may be determined according to actual circuit requirements; with further reference to fig. 3, the protection module 1 may comprise a first harmonic circuit 111 and a second harmonic circuit 112; first harmonic circuit 111 may be connected in parallel with second harmonic circuit 112; the first harmonic circuit 111 may drain a first harmonic current into the combination gang switch; the second harmonic circuit 112 may drain a second harmonic current into the combination gang switch; the first harmonic current is a harmonic current which is several times of the frequency of the fundamental current and the frequency of which is less than or equal to 1 KHz; in the present application, the frequency of the fundamental current is 50Hz, and the frequency of the first harmonic current can be 150Hz, 250Hz, 350Hz, 450Hz, etc. which are harmonic currents that are several times of the fundamental current and less than 1 KHz; and the second harmonic current is a harmonic current with a frequency greater than 1 KHz.

Further, referring to fig. 4, the first harmonic circuit 111 includes a first harmonic branch, a second harmonic branch, and a third harmonic branch; and the second harmonic circuit may include a high frequency capacitor CZ; the number of the high-frequency capacitors CZ may be one or more; the total capacitive reactance of the high-frequency capacitor of the second harmonic circuit is 158 ohm-160 ohm under the 50Hz fundamental wave and 1 ohm-2 ohm under the carrier wave of 5K; the first harmonic branch, the second harmonic branch and the third harmonic branch are connected in parallel; further, the first harmonic branch may include a first inductance L5 and a first capacitance C5; the first capacitor C5 may be connected in series with the first inductor L5; the resonant frequency of the first harmonic branch is 250Hz, and the first harmonic branch can shunt the resonant current below 250 Hz; likewise, the second harmonic branch may include a second capacitor C7 and a second inductor L7, and the second capacitor C7 and the second inductor L7 are connected in series; the resonant frequency of the second harmonic branch circuit is 350Hz, and the second harmonic branch circuit can shunt 250Hz-350Hz resonant current; likewise, the third harmonic branch may include a third capacitor C9 and a third inductor L9, where the third capacitor C9 and the third inductor L9 are connected in series; the resonant frequency of the third harmonic branch is 450Hz, and the third harmonic branch can shunt the resonant current below 350Hz-450 Hz. Furthermore, the first capacitor L5, the second capacitor L7 and the third capacitor L9 may be capacitors of 5uF to 15uF in consideration of the volume of the capacitor and the cost in practical application. The corresponding resonance frequency of the first harmonic branch circuit is 250Hz, and after the capacitance value of the capacitor is determined, the inductance value of the first inductor is also determined; similarly, for the second harmonic branch, the resonant frequency is 350Hz, and after the capacitance value of the second capacitor is determined, the inductance value of the second inductor is also determined. For the third harmonic branch, the resonant frequency is 450Hz, and after the capacitance value of the third capacitor is determined, the inductance of the third inductor is also determined, specifically, the capacitance values of the first capacitor, the second capacitor and the third capacitor are determined to be 10uF, while the inductance of the first inductor can be determined to be 40.525mH/300mA, the inductance of the second inductor can be determined to be 20.675mH/300mA, and the inductance of the third inductor can be determined to be 12.508mH/300mA. Furthermore, it should be noted that, in some embodiments of the present application, since the first harmonic circuit is used to drain the first harmonic current, when the first harmonic current is not limited to 250Hz, 350Hz, and 450Hz, other frequencies of currents are also possible, and the number of the harmonic branches is not limited to the first harmonic branch, the second harmonic branch, and the third harmonic branch; the number of harmonic branches can be increased or decreased according to the harmonic current of different frequencies to be guided.

The following description of the principle is given by taking a circuit protector applied to a three-phase circuit as an example:

because this circuit protector is applied to three-phase circuit, its protection module's quantity is 3. In the prior art, only a protection device and a main breaker linkage combination switch are arranged between a three-phase input power supply and a frequency converter, an equivalent circuit of the protection device can be seen in a diagram a of fig. 5, the equivalent of the protection device is that an impedance R2 and a reactance X2 are connected in series, and an excitation impedance Rm and an excitation reactance Xm of the protection device are branched, because an excitation current Im is very small, an initial leakage current I0 of the protection device and a current I2 entering a rectifying plate are almost equal in the prior art, and the leakage current characteristics and the content of the two are almost the same.

After the circuit protector is added, a secondary side equivalent circuit of a parallel shunt branch circuit is designed before current enters a protection device, as shown in a diagram b of fig. 5, because low-order harmonic (5-order 250Hz, 7-order 350Hz and 9-order 450 Hz) resonance LC branches are designed, low-order harmonic components in leakage current can be drained in advance and do not enter a secondary side coil, similarly, because a high-frequency harmonic capacitor Cz branch circuit is designed, high-frequency harmonic components in the leakage current can be drained in advance and do not enter the secondary side coil, finally, the current I2= I0-I9-I7-I5-Iz of the secondary side coil is ignored in a similar manner, the component of I2 is a power frequency 50Hz fundamental component, and the shunt of the leakage current is finally realized; the problem of frequent misoperation of the linkage combination switch due to low-order and high-frequency harmonic interference can be solved, the input power supply can be timely disconnected during fundamental wave 50Hz power frequency electric leakage fault, the safety of personnel and equipment is protected, and the effective protection of the AC type residual current protection device on the input side of the frequency conversion system is finally realized.

In the description of the present invention, it should be noted that, unless explicitly stated or limited otherwise, the term "switch" is to be interpreted broadly, for example, as a change or a transition; the specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In the description of the present specification, a description with reference to terms means that a specific structure or feature described in connection with an embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims (10)

1. A circuit protector is characterized in that the circuit protector is used for being connected with a combined linked switch in parallel and comprises a plurality of protection modules;

wherein the protection module comprises a first harmonic circuit and a second harmonic circuit; the first harmonic circuit is connected in parallel with the second harmonic circuit; the first harmonic circuit is used for draining a first harmonic current entering the combined gang switch; the second harmonic circuit is used for draining second harmonic current entering the combined gang switch; the first harmonic current is a harmonic current which is several times of the frequency of the fundamental current and the frequency of which is less than or equal to 1 KHz; the second harmonic current is a harmonic current with frequency greater than 1 KHz.

2. A circuit protector as claimed in claim 1, characterised in that the first harmonic circuit comprises a first harmonic branch, a second harmonic branch and a third harmonic branch; the first harmonic branch, the second harmonic branch and the third harmonic branch are connected in parallel.

3. A circuit protector according to claim 1 wherein the second harmonic circuit comprises a high frequency capacitor; the capacitive reactance of the high-frequency capacitor to the 50Hz fundamental wave is 158-160 omega.

4. A circuit protector according to claim 2 wherein the first harmonic branch comprises a first inductance and a first capacitance; the first inductor is connected with the first capacitor in series; the resonant frequency of the first harmonic branch is 250Hz.

5. A circuit protector as claimed in claim 2, wherein the second harmonic branch comprises a second inductance and a second capacitance; the second inductor is connected with the second capacitor in series; the resonant frequency of the first harmonic branch is 350Hz.

6. A circuit protector according to claim 2, characterised in that the third harmonic branch comprises a third inductance and a third capacitance; the third inductor is connected with the third capacitor in series; the resonant frequency of the third harmonic branch is 450Hz.

7. A circuit protector according to claim 4, characterised in that the capacitance of the first capacitor is in the range 5uF to 15uF.

8. A circuit protector according to claim 5, characterised in that the capacitance of the second capacitor is in the range 5uF to 15uF.

9. A circuit protector according to claim 6, characterised in that the capacitance of the third capacitor is in the range 5uF to 15uF.

10. A frequency conversion circuit comprising at least one circuit protector as claimed in any one of claims 1 to 9.

Images