CN214380682U - Main circuit of frequency converter - Google Patents
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- CN214380682U CN214380682U CN202120552937.5U CN202120552937U CN214380682U CN 214380682 U CN214380682 U CN 214380682U CN 202120552937 U CN202120552937 U CN 202120552937U CN 214380682 U CN214380682 U CN 214380682U
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Abstract
The utility model relates to the technical field of frequency converters, and discloses a frequency converter main circuit with stable transverse current conversion, which comprises a first bridge arm, a second bridge arm and a third bridge arm, wherein the first bridge arm, the second bridge arm and the third bridge arm are used for converting current signals into rectangular waves with positive and negative pulses of 120 degrees; the circuit comprises a first capacitor, a third capacitor and a fifth capacitor which are connected in series; the capacitor comprises a fourth capacitor, a sixth capacitor and a second capacitor which are connected in series; the first capacitor and the third capacitor which are connected in series are respectively connected with the first bridge arm, the second bridge arm and the third bridge arm in parallel; the fourth capacitor and the sixth capacitor which are connected in series are respectively connected with the first bridge arm, the second bridge arm and the third bridge arm in parallel; the second capacitor and the fifth capacitor are respectively connected with the first bridge arm and the third bridge arm in parallel; and the first bridge arm, the second bridge arm and the third bridge arm are subjected to current conversion through the first capacitor, the second capacitor, the third capacitor, the fourth capacitor, the fifth capacitor and the sixth capacitor.
Description
Technical Field
The utility model relates to a converter technical field, more specifically say, relate to a converter main circuit.
Background
A Variable-frequency Drive (VFD) is an electric power control device that controls the operation of an ac motor by adjusting the frequency of an operating power supply using a frequency conversion technique and an electronic technique. At present, when a frequency modulation system of a frequency converter regulates and controls switching frequency and changes output voltage of the frequency converter, commutation between an upper bridge arm and a lower bridge arm is unstable, so that output current of an inverter is unstable when the inverter regulates the speed of a motor, the temperature of a coil of the motor is rapidly increased, and the motor is easily damaged when the inverter operates for a long time.
Therefore, how to improve the stability of the commutation between the upper and lower arms of the frequency converter becomes a technical problem that needs to be solved by those skilled in the art.
SUMMERY OF THE UTILITY MODEL
The to-be-solved technical problem of the utility model lies in, when the above-mentioned converter frequency modulation system to prior art is regulating and control switching frequency, changes converter output voltage, and it is unstable to change current between the upper and lower bridge arm, leads to the coil temperature of motor to rise fast, damages the defect of motor easily, provides a stable converter main circuit of horizontal change of current.
The utility model provides a technical scheme that its technical problem adopted is: a main circuit of a frequency converter is constructed, which comprises a first bridge arm, a second bridge arm and a third bridge arm which are connected in parallel,
the first bridge arm, the second bridge arm and the third bridge arm respectively receive externally input current signals and convert the current signals into rectangular waves with positive and negative pulses of 120 degrees;
the circuit comprises a first capacitor, a third capacitor and a fifth capacitor which are connected in series; and
the circuit comprises a fourth capacitor, a sixth capacitor and a second capacitor which are connected in series; wherein,
the first capacitor and the third capacitor which are connected in series are respectively connected with the first bridge arm, the second bridge arm and the third bridge arm in parallel;
the fourth capacitor and the sixth capacitor which are connected in series are respectively connected with the first bridge arm, the second bridge arm and the third bridge arm in parallel;
the second capacitor and the fifth capacitor are respectively connected with the first bridge arm and the third bridge arm in parallel;
and carrying out commutation on the first bridge arm, the second bridge arm and the third bridge arm through the first capacitor, the second capacitor, the third capacitor, the fourth capacitor, the fifth capacitor and the sixth capacitor.
In some embodiments, the first leg is formed by connecting a first thyristor and a fourth thyristor;
the second bridge arm is formed by connecting a third thyristor and a sixth thyristor;
and the third bridge arm is formed by connecting a second thyristor and a fifth thyristor.
In some embodiments, the diode further comprises a first diode and a fourth diode connected in series,
the anode of the first diode is connected with the cathode of the first thyristor;
the cathode of the fourth diode is connected with the anode of the first thyristor.
In some embodiments, the device further comprises a third diode and a sixth diode connected in series,
the anode of the third diode is connected with the cathode of the third thyristor;
and the cathode of the sixth diode is connected with the anode of the sixth thyristor.
In some embodiments, the device further comprises a fifth diode and a second diode connected in series,
the anode of the fifth diode is connected with the cathode of the fifth thyristor;
and the cathode of the second diode is connected with the anode of the second thyristor.
In some embodiments, the bridge further comprises a first inductor, one end of the first inductor is connected to one end of each of the first bridge arm, the second bridge arm and the third bridge arm,
the other end of the first inductor is connected with a power input end.
In the main circuit of the frequency converter, including the first bridge arm, the second bridge arm and the third bridge arm of parallel connection, wherein, the current signal of external input is received respectively to first bridge arm, second bridge arm and third bridge arm to convert current to first bridge arm, second bridge arm and third bridge arm through first electric capacity, second electric capacity, third electric capacity, fourth electric capacity, fifth electric capacity and sixth electric capacity for the rectangular wave of positive negative pulse for 120. Compared with the prior art, the frequency modulation system has the advantages that the bridge arms for converting current signals into rectangular waves with positive and negative pulses of 120 degrees for output and the capacitors for forcing the bridge arms to commutate are arranged, so that the problems that when the frequency modulation system of the frequency converter regulates and controls switching frequency and changes output voltage of the frequency converter, commutation between the upper bridge arm and the lower bridge arm is unstable, the coil temperature of the motor is rapidly increased, and the motor is easily damaged can be effectively solved.
Drawings
The invention will be further explained with reference to the drawings and examples, wherein:
fig. 1 is an inverter circuit diagram of an embodiment of a main circuit of a frequency converter provided by the present invention;
fig. 2a is a current path diagram of a current conversion process according to an embodiment of the bridge arm circuit provided by the present invention;
fig. 2b is a current path diagram of a commutation process according to another embodiment of the bridge arm circuit provided by the present invention;
fig. 2c is a current path diagram of a current conversion process according to still another embodiment of the bridge arm circuit provided by the present invention;
fig. 2d is a current conversion process current path diagram of a fourth embodiment of the bridge arm circuit provided by the present invention;
fig. 3 is a waveform diagram of a series diode commutation process according to an embodiment of the bridge arm circuit provided by the present invention.
Detailed Description
In order to clearly understand the technical features, objects, and effects of the present invention, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
As shown in fig. 1-3, in the first embodiment of the main circuit of the frequency converter of the present invention, the main circuit 100 of the frequency converter includes a first bridge arm (formed by connecting VT101 and VT 104), a second bridge arm (formed by connecting VT1013 and VT 106), a third bridge arm (formed by connecting VT102 and VT 105), a first capacitor C101, a second capacitor C102, a third capacitor C103, a fourth capacitor C104, a fifth capacitor C105, and a sixth capacitor C106, which are connected in parallel.
The first bridge arm, the second bridge arm and the third bridge arm respectively receive externally input current signals and convert the current signals into rectangular waves with positive and negative pulses of 120 degrees so as to regulate the speed of the motor.
Specifically, the positive and negative pulses output by the first bridge arm are 120-degree rectangular waves and are U-phase;
the positive and negative pulses output by the second bridge arm are 120-degree rectangular waves and are V-phase;
the positive and negative pulses output by the third bridge arm are 120 degrees, and the rectangular wave is W-phase, namely the phase difference of each phase is 120 degrees. And a commutation capacitor is also arranged between each bridge arm.
Specifically, the first capacitor C101 and the third capacitor C103 are connected in series, and the first capacitor C101 and the third capacitor C103 connected in series are connected in parallel with the fifth capacitor C105; and
the fourth capacitor C104 and the sixth capacitor C106 are connected in series, and the fourth capacitor C104 and the sixth capacitor C106 connected in series are connected in parallel with the second capacitor C102.
The first capacitor C101 and the third capacitor C103 which are connected in series are respectively connected with the first bridge arm, the second bridge arm and the third bridge arm in parallel;
a fourth capacitor C104 and a sixth capacitor which are connected in series are respectively connected with the first bridge arm, the second bridge arm and the third bridge arm in parallel;
a second capacitor C102 and a fifth capacitor C105 are respectively connected with the first bridge arm and the third bridge arm in parallel;
the first, second and third arms are commutated by a first, second, third, fourth, fifth and sixth capacitor C101, C102, C103, C104, C105 and C105.
Specifically, for the common anode thyristor, the polarity of one end connected to the conducting thyristor is positive, the polarity of the other end is negative, and the voltage of the capacitor not connected to the conducting thyristor is zero. The common cathode thyristor and the common anode thyristor are similar, but the polarity of the capacitor voltage is opposite.
By arranging the bridge arm for converting the current signal into the positive and negative pulses which are 120-degree rectangular waves to be output and the capacitor for forcing the bridge arm to change the current, the problems that the current change between the upper bridge arm and the lower bridge arm is unstable when the frequency modulation system of the frequency converter regulates and controls the switching frequency and changes the output voltage of the frequency converter, the coil temperature of the motor is rapidly increased, and the motor is easily damaged can be effectively solved.
In some embodiments, in order to improve the performance of the main circuit, a first thyristor VT101 and a fourth thyristor VT104 may be disposed in the first arm, a third thyristor VT103 and a sixth thyristor VT106 may be disposed in the second arm, and a second thyristor VT102 and a fifth thyristor VT105 may be disposed in the third arm.
Specifically, the first bridge arm is formed by connecting a first thyristor VT101 and a fourth thyristor VT 104;
the second bridge arm is formed by connecting a third thyristor VT103 and a sixth thyristor VT 106;
the third bridge arm is formed by connecting a second thyristor VT102 and a fifth thyristor VT 105.
In some embodiments, in order to improve the performance of the first arm, a first diode VD101 and a fourth diode VD104 may be disposed in the first arm, wherein the first diode VD101 and the fourth diode VD104 are connected in series.
Specifically, the anode of the first diode VD101 is connected to the cathode of the first thyristor VT 101;
the cathode of the fourth diode VD104 is connected to the anode of the first thyristor VT 101.
In some embodiments, in order to improve the performance of the second leg, a third diode VD103 and a sixth diode VD106 may be disposed in the second leg, wherein the third diode VD103 and the sixth diode VD106 are connected in series.
Specifically, the anode of the third diode VD103 is connected to the cathode of the third thyristor VT 103;
the cathode of the sixth diode VD106 is connected to the anode of the sixth thyristor VT 106.
In some embodiments, in order to improve the performance of the third leg, a fifth diode VD105 and a second diode VD102 may be disposed in the third leg, wherein the fifth diode VD105 is connected in series with the second diode VD 102.
Specifically, the anode of the fifth diode VD105 is connected to the cathode of the fifth thyristor VT 105;
the cathode of the second diode VD102 is connected to the anode of the second thyristor VT 102.
One end of the first capacitor C101 and one end of the fifth capacitor C105 are respectively connected to the cathode of the first thyristor VT101 and the anode of the first diode VD 101.
The other end of the first capacitor C101 is connected to the cathode of the third thyristor VT103 and one end of the third capacitor C103, respectively, and the other ends of the third capacitor C103 and the fifth capacitor C105 are connected to the cathode of the fifth thyristor VT105 and the anode of the fifth diode VD105, respectively.
One end of the fourth capacitor C104 and one end of the second capacitor C102 are respectively connected to the anode of the fourth thyristor VT104 and the cathode of the fourth diode VD 104.
The other end of the fourth capacitor C104 is connected to the anode of the sixth thyristor VT106, the cathode of the sixth diode VD106, and one end of the sixth capacitor C106.
The other end of the sixth capacitor C106 and the other end of the second capacitor C102 are respectively connected to the anode of the second thyristor VT102 and the cathode of the second diode VD 102.
In some embodiments, the inductor further includes a first inductor L101, one end of the first inductor L101 is connected to one end of each of the first bridge arm, the second bridge arm and the third bridge arm,
the other end of the first inductor L101 is connected to the power input terminal.
Specifically, the equivalent commutation capacitance: for example, when the current flowing from the first thyristor VT101 to the third thyristor VT103 is analyzed, the capacitor C113 is an equivalent capacitor formed by connecting the third capacitor C103 and the fifth capacitor C105 in series and then connecting the third capacitor C103 and the fifth capacitor C105 in parallel with the first capacitor C101.
Assuming that the capacitances of the first capacitor C101 to the sixth capacitor C106 are all C, the capacitor C113 is 3C/2.
The process of commutation from the first thyristor VT101 to the third thyristor VT 103:
before current conversion, the first thyristor VT101 and the second thyristor VT102 are conducted, and the voltage U of the capacitor C113 isC0Positive left and negative right.
The commutation process can be divided into two stages of constant current discharge and diode commutation:
a. constant current discharge phase
t1The moment triggers the VT103 to be conducted, and the first thyristor VT101 is applied with back pressure and is turned off;
Idwhen the first thyristor VT101 is switched to VT103, the capacitor C113 is discharged through the first diode VD101, the U-phase load, the W-phase load, the second diode VD102, the second thyristor VT102, the direct current power supply and the third thyristor VT103, and the discharge current is constantly IdTherefore, it is called the constant current discharge stage. u. ofC113Before the voltage drops to zero, the first thyristor VT101 bears the back pressure, and the back pressure time is more than tqThe shutdown is guaranteed.
b. Diode commutation phase
t2Time uC113Drops to zero and then the capacitor C113 charges in reverse. Neglecting the voltage drop of the load resistor, the third diode VD103 is conducted, and the current is ivThe current of the first diode VD101 is iU＝Id-iVThe first diode VD101 and the third diode VD103 are conducted at the same time, and a diode commutation stage is started;
with C113Increasing voltage and decreasing charging current ivIncreasing in size, t3Time iUIs reduced to zero, iV＝IdThe first diode VD101 is turned off after bearing the back voltage, and the diode commutation stage is finished;
t3later, the second and third thyristors VT102 and VT103 stabilize the on-state.
Waveform analysis:
when inductively loaded, uC113、iU、iVAnd uC101、uC103The waveform of (a) is shown in fig. 3;
the voltage u of each commutation capacitor is shownC101、uC103And uC105The waveform of (a);
uC101sum of waveforms uC113Identical, in the commutation process, the slave UC0Is reduced to-UC0Capacitor C103And a capacitor C105Is connected in series and then is combined with a capacitor C101In parallel, the magnitude of the voltage variation being the capacitance C101Half of that. In the course of commutation, uC103From zero to-UC0，uC105Slave UC0And then to zero, these voltages meet the requirement when the current flows from the third thyristor VT103 to the fifth thyristor VT105 after being separated by 120 °.
While the embodiments of the present invention have been described with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many modifications may be made by one skilled in the art without departing from the spirit and scope of the present invention as defined in the appended claims.
Claims (6)
1. A main circuit of a frequency converter is characterized in that,
comprises a first bridge arm, a second bridge arm and a third bridge arm which are connected in parallel,
the first bridge arm, the second bridge arm and the third bridge arm respectively receive externally input current signals and convert the current signals into rectangular waves with positive and negative pulses of 120 degrees;
the circuit comprises a first capacitor, a third capacitor and a fifth capacitor which are connected in series; and
the circuit comprises a fourth capacitor, a sixth capacitor and a second capacitor which are connected in series; wherein,
the first capacitor and the third capacitor which are connected in series are respectively connected with the first bridge arm, the second bridge arm and the third bridge arm in parallel;
the fourth capacitor and the sixth capacitor which are connected in series are respectively connected with the first bridge arm, the second bridge arm and the third bridge arm in parallel;
the second capacitor and the fifth capacitor are respectively connected with the first bridge arm and the third bridge arm in parallel;
and carrying out commutation on the first bridge arm, the second bridge arm and the third bridge arm through the first capacitor, the second capacitor, the third capacitor, the fourth capacitor, the fifth capacitor and the sixth capacitor.
2. Frequency converter main circuit according to claim 1,
the first bridge arm is formed by connecting a first thyristor and a fourth thyristor;
the second bridge arm is formed by connecting a third thyristor and a sixth thyristor;
and the third bridge arm is formed by connecting a second thyristor and a fifth thyristor.
3. Frequency converter main circuit according to claim 2,
also comprises a first diode and a fourth diode which are connected in series,
the anode of the first diode is connected with the cathode of the first thyristor;
the cathode of the fourth diode is connected with the anode of the first thyristor.
4. Frequency converter main circuit according to claim 2,
further comprises a third diode and a sixth diode connected in series,
the anode of the third diode is connected with the cathode of the third thyristor;
and the cathode of the sixth diode is connected with the anode of the sixth thyristor.
5. Frequency converter main circuit according to claim 2,
further comprises a fifth diode and a second diode connected in series,
the anode of the fifth diode is connected with the cathode of the fifth thyristor;
and the cathode of the second diode is connected with the anode of the second thyristor.
6. Frequency converter main circuit according to claim 1,
the bridge further comprises a first inductor, one end of the first inductor is respectively connected with one end of the first bridge arm, one end of the second bridge arm and one end of the third bridge arm,
the other end of the first inductor is connected with a power input end.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202120552937.5U CN214380682U (en) | 2021-03-17 | 2021-03-17 | Main circuit of frequency converter |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202120552937.5U CN214380682U (en) | 2021-03-17 | 2021-03-17 | Main circuit of frequency converter |
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| Publication Number | Publication Date |
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| CN214380682U true CN214380682U (en) | 2021-10-08 |
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| CN202120552937.5U Active CN214380682U (en) | 2021-03-17 | 2021-03-17 | Main circuit of frequency converter |
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| CN (1) | CN214380682U (en) |
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2021
- 2021-03-17 CN CN202120552937.5U patent/CN214380682U/en active Active
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