CN116031840A - Inverter short-circuit protection circuit - Google Patents
Inverter short-circuit protection circuit Download PDFInfo
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- CN116031840A CN116031840A CN202310157586.1A CN202310157586A CN116031840A CN 116031840 A CN116031840 A CN 116031840A CN 202310157586 A CN202310157586 A CN 202310157586A CN 116031840 A CN116031840 A CN 116031840A
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Abstract
The invention belongs to the technical field of circuits, and relates to an inverter short-circuit protection circuit. The invention is based on the function expansion of the existing inverter charging circuit, and the circuit is not added. The invention aims to prevent the expansion of burning loss and fire disaster by rapidly cutting off a short circuit instead of turning off an IGBT after the short circuit of an inverter. The device comprises a second switch, a first switch and a resistor, wherein the second switch is connected with the first switch in parallel after being connected in series, the second switch is firstly closed during normal operation, and the first switch is closed when the charging is performed to be above a set value, and the second switch is kept closed; in the case of short-circuit protection, the first switch is opened first, then the second switch is opened, and the short-circuit is cut off. The inverter charging circuit operates at the start of power supply, and the inverter short-circuit protection operates at the time of power failure. One circuit plays two roles at different time, the circuit is not added, the functions are added, and the safety performance of the inverter is improved.
Description
Technical Field
The invention relates to the technical field of circuit protection, in particular to a protection circuit for an inverter when short circuit occurs.
Technical Field
The inverter (also called a converter) uses a power IGBT device as a switching device, so as to realize the requirement of high-frequency switching. Because the alternating current frequency is changed, the three-phase motor can operate at variable speed, and the three-phase motor is rapidly developed in the fields of electric vehicles, rail transit, photovoltaics, industrial dragging and the like.
The inverter charging circuit is used for avoiding abrupt change of the voltage on the filter capacitor from zero to zero when direct power supply is performed, which is equivalent to short circuit, too large current and impact on a power grid; after the charging circuit is arranged, when the charging circuit starts to be electrified, the auxiliary switch is firstly closed, the power supply charges the filter capacitor through the resistor, when the voltage reaches above a set value, the main switch is closed, the auxiliary switch is opened, and the charging current is controllable due to the current limiting effect of the resistor, so that the purpose of stable electrification is achieved.
Four-quadrant rectification of an inverter and inverter circuitry have a fatal weakness: the IGB is connected in series with the power supply, the upper bridge arm and the lower bridge arm cannot be conducted simultaneously, otherwise, the power supply is short-circuited. For example, on a railway locomotive, various electrical equipment is fully installed in a limited space, the running working conditions of the locomotive change in real time, and a contactor, a motor and the like are frequently started and stopped to generate electromagnetic interference and overvoltage, so that IBGT is difficult to thoroughly avoid being out of control due to interference to a control circuit, and the overvoltage breaks down the IBGT; and the accumulation of the individual IGBT devices with time can age and fail, and short circuit can also cause the upper bridge arm and the lower bridge arm to be directly connected. Besides the IGBT itself short-circuits, there are also short-circuits caused by loads such as motor short-circuits, line-to-ground, etc.
If the IGBT device is in failure and short circuit caused by overvoltage, all the control on the IGBT gate voltage is disabled; the circuit is subjected to IGBT short circuit caused by interference, and a rapid protection circuit also acts under the condition that short circuit current is formed. Particularly like high power IGBT circuits used on railway locomotives, the fault shut-down IGBT circuits are dummy.
The inverter short circuit is a fault after all, and the occurrence probability is low, so that a special protection circuit is designed for the inverter short circuit, and if the cost and the size of the circuit are excessive, the circuit is not necessary to install and use.
The invention can quickly cut off the short circuit when the short circuit occurs without adding the circuit and expanding the functions of the existing circuit, thereby avoiding the expansion of burning loss and the occurrence of fire.
Disclosure of Invention
The invention is based on the function expansion of the charging circuit of the existing inverter as an inverter short-circuit protection circuit. The charging circuit is not added, and functions are added to the charging circuit, so that the charging circuit becomes a protection circuit when the inverter is in short-circuit protection.
The technical scheme adopted is as follows: the switch comprises a first switch, a second switch and a resistor, wherein the second switch and the resistor are connected in series and then connected with the first switch in parallel.
Preferably, in normal operation, the second switch is first closed, and when the charging current charges the filter capacitor to a value above a set value through the resistor, the first switch is closed, and the second switch is kept closed. When the work is finished, the second switch is firstly turned off, and then the first switch is turned off.
Preferably, in the event of a short-circuit protection, the first switch is opened first, and then the second switch is opened, so that the short-circuit is cut off.
The inverter charging circuit operates at the start of power supply, and the inverter short-circuit protection operates at the time of power failure. The circuit plays two roles at different time, the circuit is not added, the functions are added, the risk of burning loss is avoided, the purpose of short-circuit protection is achieved, and the safety performance of the inverter is improved.
Drawings
The invention will be further described with reference to the drawings and examples.
FIG. 1 is a schematic diagram of the present invention, labeled: circuit 1: a power supply (ac-or dc-), a current transformer ACT1; circuit 2: a first switch K1, a second switch K2 and a resistor R; circuit 3: four-quadrant rectification, filter capacitor and inverter circuit.
Description of the embodiments
The invention aims to execute a short-circuit protection circuit while turning off the IGBT, and rapidly cut off the short-circuit to avoid the expansion of burning loss and fire occurrence.
The inverter short circuit measurement method comprises the following steps: the present invention does not provide a specific method of detecting a short-circuit current, and a judgment method, by measuring a current using a current transformer on a bus, measuring an intermediate direct current voltage using a voltage sensor, measuring Vce of an IGBT, and the like.
The schematic diagram of the present invention is circuit 2 of fig. 1, and the other circuits are referred to for purposes of illustration of the present invention, and are described in detail herein.
The invention is based on the charging circuit of the existing inverter to expand the function and is used as an inverter short-circuit protection circuit.
As shown in fig. 1, the second switch K2 of the circuit 2 is connected in series with the resistor R and then connected between the points a and b, and the first switch K1 of the circuit 2 is connected between the points a and b, which corresponds to the second switch K2 being connected in parallel with the first switch K1 after being connected in series with the resistor R and then connected between the points a and b. The second switch K2 is connected to the resistor R without any front-back division.
When the circuit is normally used, after the second switch K2 is closed, the charging current charges the filter capacitor of the circuit 3 to be above a set value through the resistor R, the first switch K1 is closed, the second switch 2 and the resistor R are in short circuit, and the second switch K2 is continuously closed. When the circuit 3 or the motor M is short-circuited, the first switch K1 is turned on firstly, and as the resistor R and the second switch K2 are connected in parallel at the two ends of the first switch K1, no arc exists at the moment of opening, no burning loss can occur, all current passes through the resistor R and the second switch K2 after the first switch K1 is turned on, the short-circuit current is reduced, and then the second switch K2 is turned off, the short-circuit is cut off, and the burning loss expansion and the fire disaster are avoided.
Under the normal condition of the voltage of the circuit 1, the charging time of the charging circuit of the existing inverter is less than 1s, so that the resistance value of the charging resistor is small, the burning loss is avoided, the charging time can be shortened due to the small resistance value of the charging resistor, and the inverter is beneficial to work; however, in the case of short-circuit protection of an inverter, it is desirable to limit the short-circuit current more quickly than a small resistance value.
Therefore, when the invention is implemented, two factors can be considered, and proper resistance value and power of the resistor are selected in a compromise, so that the charging time can be met, and the second switch K2 is safely disconnected when a short circuit occurs.
Claims (3)
1. An inverter short-circuit protection circuit is characterized in that: the switch comprises a first switch, a second switch and a resistor, wherein the second switch and the resistor are connected in series and then connected with the first switch in parallel.
2. The inverter short-circuit protection circuit according to claim 1, characterized in that: when the filter capacitor is charged to be above a set value through the resistor, the first switch is closed, and the second switch is kept closed. When the work is finished, the second switch is firstly turned off, and then the first switch is turned off.
3. The inverter short-circuit protection circuit according to claim 1, characterized in that: in the case of short-circuit protection, the first switch is opened first, then the second switch is opened, and the short-circuit is cut off.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310157586.1A CN116031840A (en) | 2023-02-23 | 2023-02-23 | Inverter short-circuit protection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310157586.1A CN116031840A (en) | 2023-02-23 | 2023-02-23 | Inverter short-circuit protection circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116031840A true CN116031840A (en) | 2023-04-28 |
Family
ID=86077748
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310157586.1A Pending CN116031840A (en) | 2023-02-23 | 2023-02-23 | Inverter short-circuit protection circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116031840A (en) |
-
2023
- 2023-02-23 CN CN202310157586.1A patent/CN116031840A/en active Pending
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