CN208939815U - A kind of overcurrent protection circuit of frequency converter - Google Patents

Abstract

The utility model discloses a kind of overcurrent protection circuits of frequency converter, including overcurrent protection reference voltage unit, three-phase current output unit, overcurrent protection comparing unit and inversion gate-drive unit, the both ends of the input terminal connection thermal resistor of overcurrent protection reference voltage unit, the output sampling end of the input terminal connection three-phase inversion unit of three-phase current output unit, the output end of the output end of overcurrent protection reference voltage unit and the three-phase current output unit is all connected with the input terminal of overcurrent protection comparing unit, the input terminal of the main control unit of the output end connection frequency converter of overcurrent protection comparing unit, the input terminal of the output end connection inversion gate-drive unit of main control unit, the control terminal of the output end connection three-phase inversion unit of inversion gate-drive unit.When three-phase output voltage is greater than overcurrent protection reference data voltage, main control unit drives the movement of inversion gate-drive unit, so that three-phase inversion unit stopping alarm.

Description

A kind of overcurrent protection circuit of frequency converter

Technical field

The utility model relates to overcurrent protection electric currents, more specifically to a kind of overcurrent protection electricity of frequency converter Road.

Background technique

With the development of power electronics technology and the emergence of the power component of function admirable, make the development of inverter More prevalent with using, at present in frequency converter operation, there is frequency converter three-phase output current detection circuit overcurrent to limit base Quasi- voltage and overcurrent protection reference voltage, and overcurrent limitation reference voltage and overcurrent protection reference voltage are fixed value, When IGBT inverter module is under different operating conditions under different radiating conditions in frequency converter, using fixed reference voltage value, lack Few flexibility, so that load and frequency converter are unable to get good protection, the reliability of frequency converter is not high.

Utility model content

The purpose of the utility model is to provide a kind of overcurrent protection circuits of frequency converter, according to the resistance of thermal resistor Value variation, adjusts overcurrent protection reference voltage, protects frequency converter preferably, improve the reliability of frequency converter.

In order to achieve the above objectives, the solution of the utility model is:

A kind of overcurrent protection circuit of frequency converter, the three-phase inversion unit of this frequency converter is internal or external thermistor Device, including overcurrent protection reference voltage unit, three-phase current output unit, overcurrent protection comparing unit and inversion gate pole drive The input terminal of moving cell, the overcurrent protection reference voltage unit connects the both ends of the thermal resistor, the three-phase electricity Flow output unit input terminal connection three-phase inversion unit output sampling end, the overcurrent protection reference voltage unit it is defeated The output end of outlet and the three-phase current output unit is electrically connected the input terminal of the overcurrent protection comparing unit, described The output end of overcurrent protection comparing unit is electrically connected the input terminal of the main control unit of the frequency converter, the main control unit Output end be electrically connected the input terminal of the inversion gate-drive unit, the output end electrical connection of the inversion gate-drive unit The control terminal of the three-phase inversion unit.

It further include overcurrent limitation comparing unit, the output end of the overcurrent protection reference voltage unit and the three-phase electricity The output end of stream output unit is also electrically connected the input terminal of the overcurrent limitation comparing unit, and the overcurrent limits ratio The input terminal of the main control unit and the input terminal of the inversion gate-drive unit are electrically connected compared with the output end of unit.

After adopting the above structure, the utility model has the following beneficial effects: passing through overcurrent protection comparing unit and mistake The setting of current protection reference voltage unit, and this overcurrent protection reference voltage unit is for obtaining according to thermal resistor device Change in resistance and the overcurrent protection reference data voltage changed, overcurrent protection comparing unit is for will be from overcurrent protection base Three-phase output voltage obtained in the overcurrent protection reference data voltage and three-phase current output unit that quasi- voltage cell obtains Be compared, when three-phase output voltage be greater than overcurrent protection reference data voltage, then export overcurrent signal and give main control list Member, main control unit drive the movement of inversion gate-drive unit, the driving signal of IGBT module are closed, so that three-phase inversion unit Stopping alarm.

Further, the setting of comparing unit is limited by overcurrent, this overcurrent limitation comparing unit is used for will be from mistake The obtained three-phase in overcurrent limitation reference data voltage and three-phase current output unit that current protection reference cell obtains Output voltage is compared, and is limited reference data voltage when three-phase output voltage is greater than overcurrent, is then exported overcurrent limitation letter Number give inversion gate-drive unit and main control unit, inversion gate-drive unit turn off three-phase inversion unit IGBT drive Dynamic signal, until inversion gate-drive automatic cell generation GBT driving signal makes three contraries after overcurrent limitation blackout Become unit movement.

Detailed description of the invention

Fig. 1 is the principles of the present invention block diagram.

Fig. 2 is the circuit diagram (omitting main control unit and inversion gate-drive unit) of the utility model.

Specific embodiment

In order to which the technical solution of the utility model is explained further, below by specific embodiment come to the utility model into Row elaborates.

A kind of overcurrent protection circuit of frequency converter, existing conventional frequency converter include main control unit and are successively electrically connected Rectification unit, filter unit and the three-phase inversion unit connect, each unit are the common unit of frequency converter, therefore not reinflated are chatted It states.In the utility model, three-phase inversion unit is built-in in the usual way or thermal resistor is provided near IGBT module Rntc。

As shown in Figure 1, the overcurrent protection circuit of the utility model includes overcurrent protection reference voltage unit, three-phase electricity Flow output unit, overcurrent protection comparing unit and inversion gate-drive unit.

The both ends of the thermal resistor Rntc of the input terminal connection three-phase inversion unit of overcurrent protection reference voltage unit, The output sampling end of the input terminal connection three-phase inversion unit of three-phase current output unit, overcurrent protection reference voltage unit Output end is electrically connected the input terminal of overcurrent protection comparing unit, and the output end of three-phase current output unit is electrically connected over current protection Protect the input terminal of comparing unit, the input terminal of the output end electrical connection main control unit of overcurrent protection comparing unit, main control The input terminal of the output end electrical connection inversion gate-drive unit of unit, the output end of inversion gate-drive unit are electrically connected three-phase The control terminal of inversion unit.

In the utility model, thermal resistor is common negative temperature coefficient thermistor, this thermal resistor has Become smaller when temperature increases resistance value, temperature reduces the characteristic that resistance value becomes larger.This overcurrent protection reference voltage unit, for obtaining root The overcurrent protection reference data voltage changed according to thermal resistor change in resistance；Three-phase current output unit, for obtaining Three-phase output voltage；Overcurrent protection comparing unit, the over current protection for will be obtained from overcurrent protection reference voltage unit Shield reference data voltage is compared with three-phase output voltage obtained in three-phase current output unit, when three-phase output voltage is big In overcurrent protection reference data voltage, then overcurrent signal is exported to main control unit, main control unit drives inversion gate pole Driving unit movement, closes the driving signal of IGBT module, so that three-phase inversion unit stopping alarm.

Further, the utility model further includes overcurrent limitation comparing unit, overcurrent protection reference voltage unit The output end of output end and three-phase current output unit is also electrically connected the input terminal of overcurrent limitation comparing unit, overcurrent The output end of limitation comparing unit is electrically connected the input terminal of main control unit and the input terminal of inversion gate-drive unit.This Inversion gate-drive unit is existing conventional driving unit, therefore no longer is unfolded to describe to its physical circuit.

In the utility model, this overcurrent protection reference voltage unit can also access according to thermal resistor change in resistance and The current limit reference data voltage of variation；Overcurrent limitation comparing unit from overcurrent protection reference voltage unit for that will obtain Overcurrent limitation reference data voltage be compared with the obtained three-phase output voltage in three-phase current output unit, when three Phase output voltage is greater than overcurrent and limits reference data voltage, then exports overcurrent limitation signal to main control unit, main control Unit exports control signal and gives inversion gate-drive unit, and inversion gate-drive unit exports shutdown signal and gives three-phase inversion list Member, so that the IGBT driving signal of three-phase inversion unit turns off, until inversion gate pole drives after overcurrent limitation blackout Moving cell automatically generates IGBT driving signal, acts three-phase inversion unit.

In this way, the utility model tool is there are two types of current protection grade, rank is from gently to being followed successively by overcurrent limitation and mistake again Current protection.The overcurrent limitation operating condition little for the current-rising-rate of inverter load short-term burst, works as the utility model When current limiting signal is obtained, frequency converter does not shut down and does not alarm, only the IGBT driving signal of Temporarily Closed three-phase inversion unit； The very big operating condition of the current-rising-rate that overcurrent protection instantaneously happens suddenly for inverter load, when the utility model obtains overcurrent When protecting signal, frequency converter hard stop simultaneously issues alarm signal, if without manual reset, when restarting frequency converter IGBT driving signal will be unable to start automatically.

As shown in Fig. 2, in the utility model, overcurrent protection reference voltage unit include the first in-phase proportion amplifying circuit, In-phase proportion subtraction amplification short circuit, reference data circuit and bleeder circuit, reference data circuit is including the 19th resistance R19 and surely Diode ZD1 is pressed, the first pin of the 19th resistance R19 is electrically connected Switching Power Supply end Vcc, second pin and zener diode The cathode of ZD1 is electrically connected, the plus earth of zener diode ZD1, the company between the 19th resistance R19 and zener diode ZD1 Contact output is reference voltage Vref.

First in-phase proportion amplifying circuit includes the 7th resistance R7, the 8th resistance R8 and four-operational amplifier U4, same to phase Ratio subtraction amplification circuit includes the 25th resistance R25, the 26th resistance R26 and the 7th operational amplifier U7.

Bleeder circuit includes the first bleeder circuit, the second bleeder circuit and third bleeder circuit and the 4th bleeder circuit, this First bleeder circuit includes eleventh resistor R11 and twelfth resistor R12, the second pin connection the tenth of eleventh resistor R11 The first pin of two resistance R12, the second pin ground connection of twelfth resistor R12, also, the electricity of eleventh resistor R11 and the 12nd The tie point output hindered between R12 is first voltage, this first voltage is the overcurrent protection benchmark of three-phase current positive half-wave Voltage VA+.Second bleeder circuit includes the 15th resistance R15 and the 16th resistance R16, the second pin of the 15th resistance R15 It is electrically connected the first pin of the 16th resistance R16, the second pin ground connection of the 16th resistance R16, and the 15th resistance R15 and the Tie point output between 16 resistance R16 is second voltage, this second voltage is that the overcurrent of three-phase current positive half-wave limits Reference voltage VB+ processed.Third bleeder circuit includes thirteenth resistor R13 and the 14th resistance R14, and the of thirteenth resistor R13 Two pins connect the 14th resistance R14 the first pin, the 14th resistance R14 second pin ground connection, thirteenth resistor R13 with Tie point output between 14th resistance R14 is tertiary voltage, this tertiary voltage is the overcurrent of the negative half-wave of three-phase current Protect reference voltage VA-.4th bleeder circuit includes the 17th resistance R17 and the 18th resistance R18, the 17th resistance R17's Second pin connects the first pin of the 18th resistance R18, the second pin ground connection of the 18th resistance R18, the 17th resistance R17 And the 18th tie point output between resistance R18 is the 4th voltage, this 4th voltage is the excessively electric of the negative half-wave of three-phase current Ductility limit reference voltage VB-.

Specifically, the negative input of four-operational amplifier U4 is grounded by the 7th resistance R7, four-operational amplifier The normal phase input end of U4 meets reference voltage Vref, and the second pin of thermal resistor Rntc is connected to the fortune of the 7th resistance R7 and the 4th Between the inverting input terminal for calculating amplifier U4, the first pin of thermal resistor Rntc connects the first pin of the 8th resistance R8, The second pin of 8th resistance R8 is sequentially connected electrically the output end of four-operational amplifier U4, eleventh resistor R11 first draws First pin of foot, the first pin of the 15th resistance R15 and the 25th resistance R25, wherein reference voltage Vref is through first The second reference voltage Vref2 is exported after in-phase proportion amplifying circuit, this second reference data voltage Vref2=(Vref* (Rntc+ R8)/R7), that is, when the temperature increases, thermal resistor Rntc resistance value becomes smaller, and Vref2 voltage value becomes smaller, conversely, temperature reduces When, thermal resistor Rntc resistance value becomes larger, and Vref2 voltage value becomes larger；The second pin of 25th resistance R25 is separately connected The inverting input terminal of seven operational amplifier U7 and the first pin of the 26th resistance R26, the positive of the 7th operational amplifier U7 Input terminal is electrically connected reference voltage Vref, and the output end of the 7th operational amplifier U7 is sequentially connected the of the 26th resistance R26 First pin of two pins, the first pin of thirteenth resistor R13 and the 17th resistance R17, reference voltage Vref are same through first Third reference voltage Vref3 is exported after Phase Proportion subtraction amplification circuit, wherein third reference voltage Vref3=Vref* (R26/ R25+1)-Vref2* (R26/R25), that is, thermal resistor Rntc resistance value becomes smaller when the temperature increases, so that the voltage of Vref2 Value becomes smaller, and the voltage value of Vref3 becomes larger, conversely, thermal resistor Rntc resistance value becomes larger when the temperature decreases, makes the electricity of Vref2 Pressure value becomes larger, and the voltage value of Vref3 becomes smaller.

Wherein, since the second reference voltage Vref2 is varied with temperature, therefore overcurrent protection reference voltage VA+ and overcurrent Limitation reference voltage VB+ is also varied with temperature.Since third reference voltage Vref3 is varied with temperature, therefore overcurrent protection benchmark Voltage VA- and overcurrent limitation reference voltage VB- are also varied with temperature.

In the utility model, three-phase current output unit includes three the second in-phase proportion operational amplification circuits, and second is same Phase Proportion operational amplification circuit includes the first operational amplifier U1, first resistor R1 and second resistance R2, three contrary above-mentioned Become unit and export U, V, W three-phase current, exports three road current signal IU, IV, IW, three road electric currents letter by three current sensors Respectively with three the second one-to-one matchings of in-phase proportion operational amplification circuit, three the second in-phase proportion operations are put by number IU, IV, IW The circuit connection principle of big circuit is identical, therefore for one of them, current signal IU is accessing the first operational amplifier U1 just To input terminal, the inverting input terminal of the first operational amplifier U1 is grounded by first resistor R1, and the first operational amplifier U1's is defeated Outlet accesses in rectification circuit above-mentioned, and the first pin of second resistance R2 is connected to first resistor R1 and the first operation amplifier Between the inverting input terminal of device U1, second pin connects the output end of the first operational amplifier U1, wherein the first operation amplifier The output voltage of device U1 is equal to IU* ((R2/R1)+1).

Overcurrent protection comparing unit includes the 5th operational amplifier U5 and the 6th operational amplifier U6, and overcurrent limits ratio It include the 8th operational amplifier U8 and the 9th operational amplifier U9 compared with unit.Specifically, rectification unit above-mentioned is by three road transports It puts output sinusoidal signal waveform and is divided into positive half-wave and negative half-wave, the positive half-wave output end of rectification unit separates three branches, and first Article branch is grounded by the 9th resistance R9, obtains positive half-wave voltage, the reverse phase of Article 2 branch and the 5th operational amplification circuit U5 Input terminal electrical connection, Article 3 branch is electrically connected with the inverting input terminal of the 8th operational amplification circuit U8, and the 5th operation amplifier The normal phase input end of device U5 is electrically connected second voltage, and the normal phase input end of the 8th operational amplifier U8 is electrically connected first voltage；It is whole Minus half wave output terminal of stream unit separates three branches, and first article of branch meets reference voltage Vref by the tenth resistance R10, and second Article branch is electrically connected with the normal phase input end of the 6th operational amplifier U6, the positive of Article 3 branch and the 9th operational amplifier U9 Input terminal electrical connection, and the inverting input terminal of the 6th operational amplifier U6 accesses the 4th voltage, the 9th operational amplifier U9's is anti- Mutually input termination tertiary voltage, the output end of the 5th operational amplifier U5 and the output end of the 6th operational amplifier U6 take over electricity The input terminal of ductility limit signal, and switching voltage Vcc limits the input terminal electricity of signal by the 21st resistance R21 and overcurrent Connection；The output end of 8th operational amplifier U8 and the output end of the 9th operational amplifier U9 are electrically connected overcurrent protection signal Input terminal, and switching voltage Vcc is electrically connected by the 20th resistance R20 with the input terminal of overcurrent protection signal.

In this way, (1), when positive half-wave voltage be greater than first voltage (i.e. overcurrent protection reference voltage VA+) when, the 8th operation Amplifier U8 movement, overcurrent protection signal export make main control unit export control signal give inversion gate-drive unit, So that frequency converter hard stop and issuing alarm signal；(2), when positive half-wave voltage is greater than second voltage, (i.e. overcurrent limits base Quasi- voltage VB+) when, the movement of the 5th operational amplifier, overcurrent limitation signal, which exports, gives inversion gate-drive unit, so that inversion Gate-drive unit Temporarily Closed IGBT driving signal, to make frequency converter break-off, until overcurrent limits blackout Afterwards, inversion gate-drive unit restores IGBT driving signal automatically；(3), when negative half-wave voltage is less than tertiary voltage (i.e. overcurrent Protect reference voltage VA-) when, the 9th operational amplifier U9 movement, overcurrent protection signal output is opened in the way of aforementioned (1) Streaming current protection；(4), when negative half-wave voltage is less than the 4th voltage (i.e. overcurrent limits reference voltage VB-), the 6th operation amplifier Device U6 movement, overcurrent limit signal output, and starting current limits in the way of aforementioned (2).

A kind of overcurrent protection circuit that frequency converter is adjusted with temperature of the utility model, as the IGBT of three-phase inversion unit When module temperature changes from low to high, the decline of IGBT module withstanding current capability, protective current value needs to reduce at this time, that is, works as IGBT When module temperature increases, thermal resistor Rntc resistance value is lower, so that the second reference voltage Vref2 becomes smaller, third reference voltage Vref3 becomes larger, and positive and negative half-wave reference voltage reduces, so that overcurrent and limitation electric current level of movement reduce, thus realization pair The reliably protecting of IGBT module；When the temperature of IGBT module from high to low when, IGBT module withstanding current capability improve, protective current Value needs to improve, that is, when IGBT module temperature reduces, the resistance value of thermal resistor Rntc is got higher, so that the second reference voltage Vref2 becomes larger, and third reference voltage Vref3 becomes smaller, and positive and negative half-wave reference voltage improves, so that overcurrent and limitation electric current movement Level improves, so that the high load capability of IGBT is realized, so that IGBT is fully used.

The foregoing is merely the preferred embodiment of the present embodiment, all equalizations done with the utility model claims range Variation and modification, should belong to the scope of the claims of the utility model.

Claims (2)

1. a kind of overcurrent protection circuit of frequency converter, the three-phase inversion unit of this frequency converter is internal or external thermistor Device, it is characterised in that: including overcurrent protection reference voltage unit, three-phase current output unit, overcurrent protection comparing unit The two of the thermal resistor is connected with the input terminal of inversion gate-drive unit, the overcurrent protection reference voltage unit End, the output sampling end of the input terminal connection three-phase inversion unit of the three-phase current output unit, the overcurrent protection base It is more single that the output end of the output end of quasi- voltage cell and the three-phase current output unit is electrically connected the overcurrent protection The input terminal of member, the output end of the overcurrent protection comparing unit are electrically connected the input of the main control unit of the frequency converter End, the output end of the main control unit are electrically connected the input terminal of the inversion gate-drive unit, the inversion gate-drive The output end of unit is electrically connected the control terminal of the three-phase inversion unit.

2. a kind of overcurrent protection circuit of frequency converter according to claim 1, it is characterised in that: further include overcurrent limitation The output end of comparing unit, the output end of the overcurrent protection reference voltage unit and the three-phase current output unit also divides It is not electrically connected the input terminal of the overcurrent limitation comparing unit, the output end of the overcurrent limitation comparing unit is electrically connected respectively Connect the input terminal of the main control unit and the input terminal of the inversion gate-drive unit.