CN102916626A - Three-phase chopper control soft starter - Google Patents

Abstract

The invention relates to a three-phase chopper control soft starter. A first path of a three-phase alternating-current supply of the three-phase chopper control soft starter is connected with an A phase of a three-phase alternating current asynchronous motor via an A-phase alternating current chopper voltage regulator circuit; a second path is connected with a B phase of the three-phase alternating current asynchronous motor via a B-phase alternating current chopper voltage regulator circuit; a third path is connected with a C phase of the three-phase alternating current asynchronous motor via a C-phase alternating current chopper voltage regulator circuit; the output of a single chip is connected with the A-phase alternating current chopper voltage regulator circuit, the B-phase alternating current chopper voltage regulator circuit and the C-phase alternating current chopper voltage regulator circuit at the same time; the second path is connected with an insulated gate bipolar transistor connected with a direct current side of a three-phase uncontrolled rectifier bridge; and the three-phase uncontrolled rectifier bridge is respectively connected between the A-phase alternating current chopper voltage regulator circuit and the A phase of the three-phase alternating current asynchronous motor, between the B-phase alternating current chopper voltage regulator circuit and the B phase of the three-phase alternating current asynchronous motor, and between the three-phase alternating-current supply and the C phase of the three-phase alternating current asynchronous motor. The three-phase chopper control soft starter can continuously start; a torque ripple component is also greatly reduced, and the start is more stable.

Description

Three-phase chopping and voltage regulating soft starter

technical field

The invention relates to a three-phase AC chopping and voltage regulating soft starter.

Background technique

At present, ordinary soft starters mainly use three-phase thyristor step-down start. It uses two thyristors or bidirectional thyristors connected in series and anti-parallel in each phase in the circuit structure, and realizes step-down start by changing the conduction time of each phase voltage. This method has two important disadvantages. First, the starting torque is small, and the starting torque of the three-phase AC asynchronous motor is proportional to the square of the starting voltage. When the voltage decreases, the torque decreases with the square multiple of the starting voltage decrease; Controlled devices can only be turned off when their forward conduction current drops to zero, so the thyristor step-down soft start, the current must be intermittent, and there is a large pulsating torque.

The frequency converter is also used as a soft starter. Although the effect is better, the frequency converter is technically an AC-DC-AC structure. It first performs three-phase bridge uncontrolled rectification of the three-phase power frequency power supply, then filters the rectified output DC voltage, and finally uses pulse width modulation (PWM) technology to output a controllable AC voltage with adjustable voltage and frequency. The structure and technology of the frequency converter are complicated, and the cost is high, so it is not easy to popularize and promote in the field of soft starting of AC motors.

At present, there is still a discrete frequency variable voltage regulation soft start technology, which uses the semi-controlled characteristics of the thyristor to selectively conduct the three-phase power frequency AC power supply, thereby forming a 50/nHz voltage (n=1,2, 3...) Waveform. This technology has three important disadvantages. First, the discrete variable frequency soft starter can only provide voltages at discrete frequency points such as 50Hz, 25Hz, 16.7Hz/3, and 12.5Hz. It is a graded discrete variable frequency soft starter. Switching still has a large inrush current. Second, the power supply provided by the discrete frequency conversion soft start has a large harmonic content and unbalanced three-phase voltage. It is actually difficult to use it for soft start. Third, there is also a current Intermittent shortcomings.

To sum up, the current soft start technology generally uses semi-controlled device thyristors to achieve step-down soft start, which has the characteristics of intermittent current, large pulsating torque component, and low starting torque.

Contents of the invention

The technical problem solved by the present invention is to provide a three-phase AC chopper voltage-regulated soft starter with continuous starting current, greatly reduced starting torque ripple component and more stable starting.

For solving above-mentioned technical problem, the technical scheme that the present invention takes:

A three-phase AC chopper voltage-regulating soft starter, which is special in that it includes a three-phase AC power supply, a single-chip microcomputer, an A-phase AC chopper voltage-regulating circuit, a B-phase AC chopper voltage-regulating circuit, and a C-phase AC chopper Voltage regulating circuit, three-phase uncontrollable rectifier bridge, three-phase AC asynchronous motor, the first path of the three-phase AC power supply is connected to the A-phase of the three-phase AC asynchronous motor through the A-phase AC chopper voltage regulating circuit, and the second path is connected to the B-phase AC asynchronous motor. The phase AC chopper voltage regulating circuit is connected to the B phase of the three-phase AC asynchronous motor, and the third circuit is connected to the C phase of the three-phase AC asynchronous motor through the C-phase AC chopper voltage regulating circuit; the output of the single-chip microcomputer is connected in three ways. One path is simultaneously connected to the A-phase AC chopping and voltage-regulating circuit, the B-phase AC chopping and voltage-regulating circuit, and the C-phase AC chopping and voltage-regulating circuit; The polarity transistor is connected, and the third circuit is connected with the current transformer set between the A-phase AC chopper voltage regulating circuit and the three-phase AC asynchronous motor; the three-phase uncontrollable rectifier bridge is divided into three circuits and respectively connected to the A-phase AC chopper Between the voltage regulating circuit and the A phase of the three-phase AC asynchronous motor, between the B-phase AC chopper voltage regulating circuit and the B phase of the three-phase AC asynchronous motor, between the three-phase AC power supply and the C phase of the three-phase AC asynchronous motor between.

The output of the above-mentioned single-chip microcomputer is connected with the current transformer arranged between the A-phase AC chopper voltage regulating circuit 3 and the three-phase AC asynchronous motor.

The above-mentioned A-phase AC chopper voltage regulating circuit is composed of an insulated gate bipolar transistor IGBT1 and an insulated gate bipolar transistor IGBT2 connected in antiparallel.

The above-mentioned B-phase AC chopper voltage regulating circuit is composed of an insulated gate bipolar transistor IGBT3 and an insulated gate bipolar transistor IGBT4 connected in antiparallel.

The above-mentioned C-phase AC chopper voltage regulating circuit is composed of an insulated gate bipolar transistor IGBT5 and an insulated gate bipolar transistor IGBT6 connected in antiparallel.

The above insulated gate bipolar transistor IGBT1, IGBT2, IGBT3, IGBT4, IGBT5, IGBT6 The trigger pulse is the same.

The above-mentioned three-phase uncontrollable rectifier bridge includes diode D1, diode D2, diode D3, diode D4, diode D5, and diode D6. Diode D1 and diode D2 are connected in series to form a first-stage diode, and diode D3 and diode D4 are connected in series to form a second-stage diode. , the diode D5 and the diode D6 are connected in series to form a third-stage diode, and the three-stage diodes are connected in parallel to form a three-phase uncontrollable rectifier bridge.

A parallel protection circuit is connected to the above-mentioned A-phase AC chopper voltage regulating circuit.

A parallel protection circuit is connected to the B-phase AC chopper voltage regulating circuit.

A parallel protection circuit is connected to the above-mentioned C-phase AC chopper voltage regulating circuit.

Compared with prior art, the beneficial effect of the present invention:

The invention adopts the fully-controlled device insulated gate bipolar transistor (IGBT) to realize the AC chopping voltage regulation technology. Because the trigger pulse period of the IGBT is much smaller than the power frequency period, although the starting current of the AC motor still has small pulsations, it can be continuous, the starting torque pulsation component is also greatly reduced, and the starting is more stable.

Description of drawings

Fig. 1 is the circuit diagram of the present invention.

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment the present invention is described in detail.

Referring to Fig. 1, the present invention includes a three-phase AC power supply 1, a single-chip microcomputer 2, an A-phase AC chopping voltage regulating circuit 3, a B-phase AC chopping voltage regulating circuit 4, a C-phase AC chopping voltage regulating circuit 5, and a three-phase uncontrollable The rectifier bridge 6, the three-phase AC asynchronous motor 10, the first path of the three-phase AC power supply 1 is connected to the A-phase of the three-phase AC asynchronous motor 10 through the A-phase AC chopper voltage regulating circuit 3, and the second path is connected to the B-phase AC chopper The wave voltage regulating circuit 4 is connected with the B phase of the three-phase AC asynchronous motor 10, and the third circuit is connected with the C phase of the three-phase AC asynchronous motor 10 through the C-phase AC chopper voltage regulating circuit 5; the output of the single-chip microcomputer 2 is connected in three ways , the first road is simultaneously connected with the A-phase AC chopping and voltage-regulating circuit 3, the B-phase AC chopping and voltage-regulating circuit 4, and the C-phase AC chopping and voltage-regulating circuit 5, and the second road is connected with the DC side of the three-phase uncontrollable rectifier bridge 5 connected to the insulated gate bipolar transistor 6, and the third circuit is connected to the current transformer 8 arranged between the A-phase AC chopper voltage regulator circuit 3 and the three-phase AC asynchronous motor 9; the three-phase uncontrollable rectifier bridge 6 Divided into three circuits, respectively connected between the A-phase AC chopper voltage regulator circuit 3 and the A phase of the three-phase AC asynchronous motor 10, between the B-phase AC chopper voltage regulator circuit 4 and the B phase of the three-phase AC asynchronous motor 10, Between the C-phase AC chopper voltage regulator circuit 5 and the C-phase of the three-phase AC asynchronous motor 10 .

The output of the above-mentioned single-chip microcomputer 2 is connected with the current transformer 9 arranged between the A-phase AC chopper voltage regulator circuit 3 and the three-phase AC asynchronous motor 10 .

The above-mentioned A-phase AC chopper voltage regulating circuit 3 is composed of an insulated gate bipolar transistor IGBT1 and an insulated gate bipolar transistor IGBT2 connected in antiparallel.

The above-mentioned B-phase AC chopper voltage regulator circuit 4 is composed of an insulated gate bipolar transistor IGBT3 and an insulated gate bipolar transistor IGBT4 connected in antiparallel.

The above-mentioned C-phase AC chopper voltage regulating circuit 5 is composed of an insulated gate bipolar transistor IGBT5 and an insulated gate bipolar transistor IGBT6 connected in antiparallel.

The above insulated gate bipolar transistor IGBT1, IGBT2, IGBT3, IGBT4, IGBT5, IGBT6 The trigger pulse is the same.

The above-mentioned three-phase uncontrollable rectifier bridge 6 includes diode D1, diode D2, diode D3, diode D4, diode D5, and diode D6. Diode D1 and diode D2 are connected in series to form the first stage diode, and diode D3 and diode D4 are connected in series to form the second stage. The diodes, the diode D5 and the diode D6 are connected in series to form a third-stage diode, and the three-stage diodes are connected in parallel to form a three-phase uncontrollable rectifier bridge 6 .

A parallel protection circuit 8 is connected to the above-mentioned A-phase AC chopper voltage regulating circuit 3 .

A parallel protection circuit 8 is connected to the above-mentioned B-phase AC chopper voltage regulating circuit 4 .

A parallel protection circuit 8 is connected to the above-mentioned C-phase AC chopper voltage regulator circuit 5 .

In the structure of the main circuit, six insulated gate bipolar transistors are used, and each two are connected in anti-parallel to form three groups of A-phase AC chopping and voltage regulating circuit 3, B-phase AC chopping and voltage-regulating circuit 4, and C-phase AC The chopper voltage regulating circuit 5 is respectively connected in series between the three-phase AC power supply 1 and the A-phase, B-phase and C-phase stator windings of the three-phase AC asynchronous motor 10 . Another six diodes are used to form a three-phase bridge-type uncontrollable rectifier bridge 6, and the AC side of the three-phase uncontrollable rectifier bridge is connected between the AC voltage regulating circuit and the stator winding of the three-phase AC asynchronous motor, and the three-phase uncontrollable rectifier bridge The direct current side is connected with an insulated gate bipolar transistor 7. In order to protect the IGBTs, each IGBT is connected in parallel with an RC series protection circuit. In order to detect and control the starting current, a current transformer 9 is installed on the A-phase power line of the three-phase AC asynchronous motor side, and the current signal detected by the current transformer is sent to the single-chip microcomputer 2 .

In the control of the main circuit, there are two control pulses generated by the single-chip microcomputer system, and one pulse triggers three groups of A-phase AC chopping and voltage-regulating circuit 3, B-phase AC chopping and voltage-regulating circuit 4, and C-phase AC chopping and voltage-regulating circuit 5 A set of AC chopper voltage regulating device, another pulse triggers the insulated gate bipolar transistor 7 on the DC side of the three-phase uncontrollable rectifier bridge, the positive and negative of the two pulses are completely opposite, and the pulse frequency is 1KHz. In this way, at the moment when the A-phase AC chopper voltage regulator circuit 3, the B-phase AC chopper voltage regulator circuit 4, and the C-phase AC chopper voltage regulator circuit 5 are turned on, the insulated gate bipolar transistor 7 is turned off, and the three-phase The AC power supply 1 supplies power to the three-phase AC asynchronous motor. When the A-phase AC chopping and voltage-regulating circuit 3, the B-phase AC chopping and voltage-regulating circuit 4, and the C-phase AC chopping and voltage-regulating circuit 5 are turned off, the insulating grid bipolar The transistor 7 is triggered and turned on, and the stator current of the three-phase AC asynchronous motor continues to flow through the three-phase uncontrollable rectifier bridge 6 .

In the control algorithm, in order to realize the soft start control or soft stop control of the three-phase AC asynchronous motor. Specifically, there are two control methods. First, ramp voltage startup is completed according to a preset curve. It is an open-loop control method. In this case, the current transformer 9 may not be installed. According to the pre-calculated minimum voltage Umin and the starting time, the duty ratio α of the chopping modulation pulse is linearly adjusted until α is 100%. The output voltage It is the full voltage of the three-phase AC voltage. At this time, the three-phase AC asynchronous motor can be switched to the three-phase AC power supply through an additional bypass three-phase AC contactor. Complete the ramp voltage soft start of the three-phase AC asynchronous motor. Second, constant current soft start. The maximum allowable starting current Imax is preset in the single-chip microcomputer, and the current actual current I is detected by the current transformer 9. A digital PID controller with a limiter output is set in the single-chip microcomputer system. The input of the PID controller is the maximum allowable starting current Imax and The deviation of the actual current I, the output of the PID controller is the duty cycle α of the chopping modulation pulse, the upper limit of the output of the PID controller is 100%, and the lower limit is 0%.

In the formula, T is the current sampling period, k is the kth sampling period, Ti is the integral time constant of the PID controller, and Td is the differential time constant of the PID controller.

If the soft stop function of the three-phase AC asynchronous motor is realized, the duty cycle α of the chopper modulation pulse can be adjusted in the opposite direction of the slope voltage soft start, so that α gradually decreases from 100%, and the effective value of the output AC voltage gradually decreases. Lower until a soft stop is achieved.

The present invention is compared with the three-phase thyristor voltage regulating soft start technology in the simulation experiment. The experimental object is a three-phase AC asynchronous motor with a rated power of 15KW, a rated voltage of 400V, and a rated frequency of 50Hz. The motor load is 15Nm. The experimental environment is MatlabR2008a.

Comparison 1: The same output fundamental voltage RMS, the same load.

Three-phase thyristor voltage regulation soft start, the thyristor trigger angle is set to 90 degrees, when the symmetrical three-phase pure resistance load is used, the effective value of the fundamental wave of the output line voltage is 175.4V, the total harmonic content: 60.85%, and the starting current is 150A.

Three-phase chopper voltage regulation soft start, the duty cycle of the trigger pulse is 46%, the effective value of the fundamental wave voltage of the output line is 175.4V, the total harmonic content is 101%, and the starting current is 130A.

It can be seen from the above data that under the same effective value of the fundamental voltage, the starting current of the two-phase chopper modulation soft start is small. Although the harmonic content of the two-phase chopping modulation soft start is relatively large, its harmonics are mainly high-order harmonics (19th, 21st, 49th, 51st, etc.), and the generated AC current is small, which affects the motor. smaller.

Comparison 2: Under the same maximum allowable starting current (5 times the rated current, 150A), the maximum load that the three-phase chopper voltage regulation soft start can start is 95Nm, while the three-phase thyristor voltage regulation soft start can start the maximum load is 85Nm.

Claims (10)

1. three-phase alternating current chopper control soft starter, it is characterized in that: comprise three-phase alternating-current supply (1), single-chip microcomputer (2), A cross streams voltage regulation circuit of chopping (3), B cross streams voltage regulation circuit of chopping (4), C cross streams voltage regulation circuit of chopping (5), the uncontrollable rectifier bridge of three-phase (6), three-phase AC asynchronous motor (10), the first via of three-phase alternating-current supply (1) is connected through the A of A cross streams voltage regulation circuit of chopping (3) with three-phase AC asynchronous motor (10), the second the tunnel is connected through the B of B cross streams voltage regulation circuit of chopping (4) with three-phase AC asynchronous motor (10), and Third Road is connected through the C of C cross streams voltage regulation circuit of chopping (5) with three-phase AC asynchronous motor (10); The output of single-chip microcomputer (2) divides three the tunnel to connect, the first via is connected with A cross streams voltage regulation circuit of chopping (3), B cross streams voltage regulation circuit of chopping (4), C cross streams voltage regulation circuit of chopping (5) simultaneously, the second the tunnel is connected with the insulated gate bipolar transistor (6) of the uncontrollable rectifier bridge of three-phase (5) direct current side joint, Third Road be arranged on A cross streams voltage regulation circuit of chopping (3) and be connected with current transformer (8) between the three-phase AC asynchronous motor (9); The A that the uncontrollable rectifier bridge of three-phase (6) Fen Sanlu is connected to A cross streams voltage regulation circuit of chopping (3) and three-phase AC asynchronous motor (10) mutually between, the B of B cross streams voltage regulation circuit of chopping (4) and three-phase AC asynchronous motor (10) mutually between, three-phase alternating-current supply (1) and three-phase AC asynchronous motor (10) the C phase between.

2. three-phase alternating current chopper control soft starter according to claim 1 is characterized in that: the output of described single-chip microcomputer (2) be arranged on A cross streams voltage regulation circuit of chopping (3) and be connected with current transformer (9) between the three-phase AC asynchronous motor (10).

3. three-phase alternating current chopper control soft starter according to claim 1 and 2, it is characterized in that: described A cross streams voltage regulation circuit of chopping (3) is made of insulated gate bipolar transistor IGBT1, insulated gate bipolar transistor IGBT2 inverse parallel.

4. three-phase alternating current chopper control soft starter according to claim 3, it is characterized in that: described B cross streams voltage regulation circuit of chopping (4) is made of insulated gate bipolar transistor IGBT3, insulated gate bipolar transistor IGBT4 inverse parallel.

5. three-phase alternating current chopper control soft starter according to claim 4, it is characterized in that: described C cross streams voltage regulation circuit of chopping (5) is made of insulated gate bipolar transistor IGBT5, insulated gate bipolar transistor IGBT6 inverse parallel.

6. three-phase alternating current chopper control soft starter according to claim 5, it is characterized in that: the trigger impulse of described insulated gate bipolar transistor IGBT1, insulated gate bipolar transistor IGBT2, insulated gate bipolar transistor IGBT3, insulated gate bipolar transistor IGBT4, insulated gate bipolar transistor IGBT5, insulated gate bipolar transistor IGBT6 is identical.

7. three-phase alternating current chopper control soft starter according to claim 6, it is characterized in that: the uncontrollable rectifier bridge of described three-phase (6) comprises diode D1, diode D2, diode D3, diode D4, diode D5, diode D6, diode D1 and diode D2 series connection consist of first order diode, diode D3 and diode D4 series connection consist of second level diode, diode D5 and diode D6 series connection consist of third level diode, and three grades of diodes in parallels consist of the uncontrollable rectifier bridge of three-phase (6).

8. three-phase alternating current chopper control soft starter according to claim 7 is characterized in that: be connected with parallel connection protection circuit (8) on the described A cross streams voltage regulation circuit of chopping (3).

9. three-phase alternating current chopper control soft starter according to claim 8 is characterized in that: be connected with parallel connection protection circuit (8) on the described B cross streams voltage regulation circuit of chopping (4).

10. three-phase alternating current chopper control soft starter according to claim 9 is characterized in that: be connected with parallel connection protection circuit (8) on the described C cross streams voltage regulation circuit of chopping (5).

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