JPS58112498A - Inverter device - Google Patents

Abstract

PURPOSE:To shorten the idling time of a motor by increasing the magnetic flux of the motor when the motor is shifted from braking operation to idling operation and increasing the loss. CONSTITUTION:A voltage type inverter device is composed of a main circuitI and a control circuit II. When the output of a comparator 19 which compares the output of a voltage detector 17 with the set value of a voltage setter 18 is generated and a motor 4 shifts from braking operation to idling operation, the gain of a voltage controller 21 is increased, and the terminal voltage of the motor 4 is raised. The frequency at this time is constant since the output signal of an acceleration or deceleration limiter 12 is clamped. Accordingly, the magnetic flux of the motor 4 increases, the iron loss of the motor 4 increases, and the exciting current increases, thereby inccreasing the copper loss. The energy stored in the capacitor 2 is consumed early by these losses.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a voltage source inverter, and particularly to an inverter device that provides overpressure protection and can perform deceleration operation in a short time.

TECHNICAL BACKGROUND OF THE INVENTION Conventionally, when variable speed operation of an AC motor is performed using a voltage source inverter, when decelerating the motor is subjected to rotational braking, the load GD2 is large, and the inverter 1111 is connected from the LJR combined motor side that performs rapid deceleration. A large amount of electrical energy is returned, and the snow pressure at the terminals of the main circulation capacitor increases. For this reason, many methods have been adopted to protect the inverter from overvoltage, including a device that detects the terminal voltage of the main 101-path capacitor, and automatically stops the deceleration operation when the voltage rises above the detection level. ing.

Figure 1 shows the configuration of this type of conventional [1 pressure type inverter device] in a professional manner.
and a control circuit section 11.

-First, the main circuit section I consists of a rectifier section 1 that receives commercial power and converts it into direct current, a capacitor 2 that smoothes this rectified voltage, and a control circuit section that sequentially switches semiconductor elements in accordance with signals from the control circuit section ■. The AC motor 4 is comprised of an inverter section 3 which obtains alternating current through the inverter section 3, and an alternating current motor 4 as a load to which the alternating current output from the inverter section 3 is supplied. Here, the inverter section 3 consists of six transistors 301 and six diodes 302 as semiconductor switching elements.

On the other hand, in the control circuit section (2), reference numeral 11 is a frequency setter, and its output signal a is input to an acceleration/deceleration limiting circuit 12.

This acceleration/deceleration limiting circuit 12 includes, for example, an integrator that provides an output signal a of the circuit in question, and compares the output signal of this integrator with the output signal a of the frequency setter 11 to provide an input signal of the integrator. As a result, the output signal follows the change in the input signal a at a predetermined gradient and is output. The relationship of changes in the input and output voltage signals a and b with respect to time t is shown in FIG. 2. This acceleration/deceleration 11tl+output signal of the limiting circuit 12 is the output signal of the voltage control circuit 13 and the voltage frequency conversion circuit (VFC) I
4 respectively. The voltage control circuit 13 is for determining the output voltage of the inverter, and the voltage/frequency conversion circuit 14 is for determining the output frequency of the inverter. Here, the relationship between the input and output voltage signals of the voltage control circuit 13 is shown in FIG. In the figure, G-1 indicates that the dyne of the path is 1, and in this case, input=output. Similarly [G = 2 indicates that the dyne is 2, and the output voltage C is twice as large as the input voltage and pressure.
becomes. Note that this circuit 13 limits the maximum signal to IOV, so when G=2, the output between 5V and 10VO is constant at 1()■. Further, the voltage/frequency conversion circuit 14 is a kind of analog/digital conversion circuit, and outputs a frequency proportional to the input signal.

Next, the output signal of the voltage control circuit 13 is applied to the modulation circuit 15 together with the output signal of the voltage/frequency conversion circuit 14. This modulation circuit 15 forms control pulses for individual transistors for controlling the signal width modulation of the ear/sp section 3. The fundamental wave number of the output voltage of the in/out part 3 is proportional to the frequency of the output signal of the voltage-frequency converter 14, and therefore to the output signal of the acceleration/deceleration limiting circuit 12. On the other hand, the output voltage of the inverter s3 is determined by on/off control of the transistor, and the width of each signal is determined by the output signal C of the voltage control circuit 13. The output signal of the modulation circuit 15 is input to the pace drive circuit 16, and this pace drive circuit 16 generates a pace voltage of 5.
− It is used for switching transistors with pace current.

In this way, the AC motor 4 can be operated with a variable frequency power source. By the way, if a deceleration command is suddenly input using the frequency setting device 1 while the AC motor 4 is being operated by the voltage type inverter as described above, the stator frequency f of the commercial
1) The rotor rotation frequency becomes f2, the AC motor 4 operates as a generator, and the rotational energy of the GD20 connected to the rotor is converted into electrical energy, which is then transferred to the capacitor 2 via the diode 302 of the inverter section 3. be regenerated. The energy regenerated into the capacitor 2 results in an increase in the terminal voltage of the capacitor 2, and if the motor 4 load GD2 is large and decelerates in a short period of time, the capacitor 2 voltage increases rapidly. This will cause the result. Therefore, if the speed command pattern during braking is inappropriate as described above, the voltage rise will be very large, and there is a risk that the semiconductor element will be destroyed.

6- Therefore, generally, as shown in FIG. 1, the output signal of the voltage detection circuit 17 that detects the voltage of the capacitor 2 and the output signal of the setting device 18 that sets a predetermined upper limit value of the capacitor voltage are set to have hysteresis characteristics. When the voltage of the capacitor 2 exceeds a predetermined limit (1M) during control, the comparator 23 It operates and the output signal V
COM is sent out, and the frequency command value is held by this output signal vcoM. This frequency command value can be held, for example, by forcibly setting the input of the integrator in the acceleration/deceleration limiting circuit 12 to zero. Therefore, while the output signal vcoM of the comparator 19 is being generated, the deceleration command is interrupted.

On the other hand, when the capacitor voltage decreases to the normal range, the output signal vco- of the comparator 19 disappears, the hold action is released, and the shield wave number command value decreases again at the predetermined i4 turn. Then, if the voltage of the capacitor 2 exceeds the predetermined upper limit again, the same operation as described above is repeated.

FIG. 4 shows a specific example of such operation in the form of a time chart. In the figure, ■, is the output signal of the frequency setter 11, vc is the terminal voltage of the capacitor 2, and vb
is the output signal of the acceleration/deceleration limiting circuit 12, and vcoM is the output signal of the comparator 1.
9 shows the time course of the output signals of No. 9, respectively.

Now, at time to, the output signal va of the frequency setter 11 is r
o'' VC is dropped and a stop command is issued.

As a result, the output No. 718 of the addition/subtraction limiting circuit 12 is V.

turns to "0" at a predetermined slope and begins to decrease, the AC motor 4 shifts to power generation operation, and the capacitor 2 is charged with the old energy. Then, at the time tl when this charging pressure vc reaches the upper limit value VIK, the output signal V of the comparator 23. is inverted, and this causes acceleration/deceleration input limiting circuit 1
The output signal v5 of No. 2 is held at its previous value. As a result, the regenerated energy from the motor 4 to the capacitor 2 decreases, and the charged energy is mainly consumed as copper loss in the motor, so the capacitor voltage vc decreases. Next, at time t2, the capacitor voltage vc is lower limit value v
When the value reaches 2, the hold operation of the acceleration/deceleration limiting circuit 12 is released and the operation of lowering the output signal vb is restarted. As a result, the capacitor voltage V again. increases, and when it reaches the upper limit value vl again at time a t 3, the output signal Vb of the acceleration/deceleration limiting circuit 12 is held. Thereafter, the electric motor 4 repeatedly brakes and coasts in the same manner until it stops.

Problems with the Background Art Naturally, when overvoltage protection is applied to an inverter device having the above-mentioned functions, coasting time is automatically added to speed time to consume the regenerated energy. However, it will slow down. Therefore, when it is desired to decelerate the electric motor 4 in a short period of time, an inverter device equipped with such an overvoltage protection means is insufficient.

9- Purpose of the Invention The present invention was made to solve the problems of the prior art as described above, and its purpose is to ensure overvoltage protection of the device and to complete the deceleration operation in a short time. We will provide you with an advance payment for inverter installation.

Summary of the Invention In order to achieve the above object, the present invention sequentially switches a rectifier section that inputs a commercial power source and converts it into direct current, a capacitor that smoothes the direct current from this rectifier section, and a semiconductor switching element. The main circuit section consists of an inverter section that converts the above-mentioned direct current into alternating current and supplies the alternating current to a load such as a motor, a frequency setting device, and an output signal from the frequency setting device that is inputted and a predetermined response to the change. an acceleration/deceleration limiting circuit that follows and outputs the acceleration/deceleration limiting circuit; a voltage control circuit that determines the inverter output voltage based on the output signal from the acceleration/deceleration limiting circuit and is capable of varying its gain; and an output from the acceleration/deceleration limiting circuit. Based on each signal, the semiconductor switch of the inverter section is input 9 times and 10 times.

a circuit that sequentially controls switching of the switching elements; and a circuit that detects the voltage of the capacitor and, on condition that the magnitude thereof is greater than a predetermined value, holds the output of the acceleration/deceleration limiting circuit and increases the gain of the voltage control circuit. An inverter device is constructed from a control circuit section consisting of an overvoltage protection circuit,
When the capacitor voltage reaches a predetermined value or more, the frequency lowering operation of the inverter as a brake is temporarily interrupted and the dyne of the voltage control circuit output is increased.

Embodiments of the Invention First, generally speaking, in the above-mentioned inverter device, the relationship between the energy N stored in the capacitor due to regenerative braking and the energy Wo regenerated when the motor operates as a generator is expressed by the following equation.

Δw=w, −w, −wL ・−・−・・・・
・・・−・−・・−・−・・・・ ill and where, Wl
,! is the energy lost within the motor, and the energy lost between the WL motor terminal and the capacitor terminal. As seen from the above formula, to reduce the energy stored in the capacitor, the energy lost in the motor W1
4, it is sufficient to increase the loss WL between the motor and the capacitor.

The present invention is based on this principle, and the voltage control circuit 13 receives the output signal V from the comparator 19. It provides OM and makes it possible to increase its key.

Hereinafter, an embodiment of the present invention based on the above principle shown in FIG. 5 will be described. In addition, in the figure, the same parts as in FIG. 1 are given the same reference numerals, and the explanation thereof will be omitted. That is, in FIG. 5, when the output of the comparator 19σ) is input to the acceleration/deceleration limiting circuit 12, it is input to the voltage control circuit as well as L). Here, the voltage control circuit 21 is the acceleration/deceleration control circuit 12.
The direct voltage V of the dyne is preset from the output signal voltage vbvC from the dyne. In addition to outputting , the gain can be varied (increased) by the output signal vco4 from the comparison '4519.

FIG. 6 shows an example of the configuration of the voltage control circuit 21, and as shown in the figure, the input resistance RI r of two operational amplifiers OA is
This can be easily realized by providing a switch Sw that closes when the signal VCOM from the comparator 19 is present on one side of R2. That is, the voltage control voltage when the switch SW is open is as follows, and it is possible to increase the gain of the amplifier compared to when the switch SW is closed.

By configuring the inverter device in this manner, when the output signal of the comparator 19 is generated and the motor 4 shifts from braking operation to coasting operation, the voltage ? By increasing the din of the Itll wJ circuit 21, the terminal voltage of the motor 4 is increased.

At this time, the frequency is 13- of the acceleration/deceleration limiting circuit 12. The output No. 1g is clamped and is constant.

Therefore, at this time, the magnetic flux density of the electric motor 4 increases, the iron loss of the electric motor 4 increases, and the copper loss increases due to the increase in exciting current. By adding these losses by 1, the energy stored in the capacitor 2 is quickly consumed, thereby shortening the coasting time and the electric motor 4 returns to the braking state. Note that the other functions are the same as those of the prior art described above, and will not be described here.

In this way, the rectifier section 1 inputs commercial power and converts it into direct current, the capacitor 2 smoothes the direct current from this rectifier section 1, and the semiconductor switching elements 301 and 302 are sequentially switched to convert the direct current into alternating current. A main circuit section 11 consisting of an inverter section 3 that converts and supplies the AC motor to an AC motor; The inverter output voltage is determined based on the output signal from the acceleration/deceleration limiting circuit 12 and the acceleration/deceleration limiting circuit 12, and voltage control 14- is capable of varying the gain [i1 path 21 and the output signal from the acceleration/deceleration limiting circuit 12]. Based on the output signals, the inverter section 30 semiconductor switching elements 301, 302f
The f-key and pace drive circuits 15 and 16 which sequentially control switching and the voltage of the upper d1 capacitor 2 are detected, and the output of the acceleration/deceleration limiting circuit 12 is controlled on the condition that the voltage is greater than a predetermined upper limit value. A vehicle pressure detection circuit 17 that holds the voltage and increases the gain of the voltage control circuit 21.
An inverter device is constructed from a control circuit section 11 consisting of an overvoltage pupil maintenance circuit, which is constituted by a setting device 18 and a comparator 19.

Therefore, since overvoltage detection during braking by the engine braking system may increase the number of motors 41 lost during coasting operation, the coasting time can be significantly shortened to complete the deceleration operation in a short time and improve coordination. Rich driving becomes 1JT ability, and in-training
It is possible to reliably protect the computer equipment from overvoltage.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, the present invention provides a highly reliable inverter device that can reliably protect the device from overvoltage and can complete a deceleration operation in an extremely short time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional voltage-type interface device, FIG. 2 is a diagram for explaining the operation of the acceleration/deceleration limiting circuit, and FIG. 3 is a diagram for explaining the operation of the voltage control circuit. Figure 4 is an operating waveform diagram in Figure @1, Figure 5 is a block diagram showing the voltage source inverter device of the present invention, and Figure 6 is a block diagram of the voltage control circuit in Figure 5. DESCRIPTION OF SYMBOLS 1... Rectifier part, 2... Capacitor, 3... Inverter part, 301... Transistor, 3o2... Diode, 4... AC motor, 1)... Frequency setting device, 12... ... Acceleration/deceleration limiting circuit, 13... Voltage control circuit, 14... Voltage/frequency conversion circuit, 15... Modulation circuit, 16... Pace drive circuit, 17... Voltage detection circuit, 18. ... Voltage setting device, 19... Comparator,
21... Voltage control circuit. Applicant's agent Patent attorney Takehiko Suzue 17- Figure 1

Claims (1)

[Claims] An AC motor that converts the DC into AC by sequentially switching a rectifier section that receives commercial power and converts it into DC, a capacitor that smoothes the DC from the rectifier, and a semiconductor switching element. a main circuit section consisting of an inverter section that supplies the load to the load, a frequency setter, and an acceleration/deceleration limiting circuit that receives the output signal from the frequency setter and follows the change at a predetermined gradient and outputs the output signal. , a voltage control circuit capable of controlling the in/output voltage based on the output signal from the acceleration/deceleration limiting circuit and making the r-in variable; A circuit that sequentially controls the switching of the semiconductor switching elements of the inverter section based on each output from the control circuit, and a circuit that detects the heavy pressure of the capacitor and controls the acceleration/deceleration limit on the condition that the magnitude is greater than a predetermined value. 1. An inverter device comprising a control circuit section that holds the output of the circuit and also includes an over-removal pressure protection circuit that maintains a high level of r-in of the voltage control circuit.