JPH1126145A - Control device for inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To operate an inverter device without restricting the position of a heating object material existing in a load coil or the size of the material, a construction material or the like, that is, load impedance. SOLUTION: This device has a size discriminating means to discriminate the size relationship between both by comparing an AC input current level of an inverter device after an electronic power inverter 3 starts operation with a preset prescribed reference current level and a control means to increase/ decrease a voltage control signal of a constant time electronic power rectifier 1 so that a control angle α of the electronic power rectifier 1 becomes a delay directional fixed control angle α1 when discriminated that the AC input current level is larger than the reference current level or the control angle α of the electronic power rectifier 1 becomes an advance directional fixed control angle α1 when discriminated that the AC input current level is smaller than the reference current level on the basis of a discriminating result by the size discriminating means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a load commutation type inverter device used for inductively heating a material to be heated such as a metal material, and more particularly to a control device for starting a high impedance or low impedance load of the inverter device. The present invention relates to a control device for an inverter device in which control of the inverter device is improved.

[0002]

2. Description of the Related Art FIG. 9 is a block diagram showing an example of the configuration of a conventional control device for an inverter device of this kind. In FIG. 9, the inverter device includes a forward converter 1 including a thyristor, a DC reactor 2, and an inverse converter 3 including a thyristor.

A forward converter 1 converts AC power into DC power and supplies DC power to an inverter 3 via a DC reactor 2. Inverter 3 converts the DC power converted by forward converter 1 into high-frequency AC power, and supplies high-frequency power to parallel resonance load 7 including power factor improving capacitor 71 and load coil 72.

On the other hand, the starting circuit 4 is a circuit for switching the inverter 3 from a bypass pair operation in which the U-phase and the X-phase or a V-phase and the Y-phase are simultaneously fired to a high-frequency operation. The material to be heated 8 is generated by eddy current loss with high-frequency magnetic flux generated from the load coil 72 and is induction-heated.

On the other hand, a transformer 5 detects an output voltage of the inverter device, a transformer 6 detects an AC input current of the inverter device, and a voltage conversion circuit 9 controls a voltage for controlling the AC output voltage. The current conversion circuit 10 converts the detection value from the current transformer 6 into an appropriate value in order to control the AC input current.

The voltage reference setting device 11 sets the AC output voltage of the inverter device, and the adder 12 converts the voltage reference value set by the voltage reference setting device 11 and the output voltage from the voltage conversion circuit 9. The voltages are added with the polarity shown in the figure, and the voltage control adjuster 13 controls the voltage based on the output from the adder 12.

Further, the current reference setting device 14 sets the AC input current of the inverter device, and the adder 15 uses the current reference value set by the current reference setting device 14 and the current conversion circuit 1.
The output current from 0 is added with the polarity shown in the figure, and the current control adjuster 16 controls the current based on the output from the adder 15.

Further, the high-level priority circuit 17 compares the output from the voltage control regulator 13 with the output from the current control regulator 16 and selects the output with the higher output level to select the higher output. Output to The output of the phase control circuit 18 is provided to the forward converter 1 as a gate signal.

[0009] By the way, when induction heating of the material to be heated 8 is performed by an inverter device as shown in FIG. 9, if the tip of the material to be heated 8 is properly inserted inside the load coil 72, Since the material to be heated 8 is present inside, power is applied to the material to be heated 8, so that the load impedance seen from the inverter device falls within the operable range of impedance.

However, in a state where the material to be heated 8 is not sufficiently inserted into the load coil 72, when the inverter device is started, the load impedance becomes high since the material to be heated 8 is not present in the load coil 72, and the load impedance becomes high. The DC current required for the operation of the device cannot be supplied, and the DC current is intermittent and cannot be operated.

On the other hand, when the operation is performed with the material to be heated 8 completely inserted into the load coil 72, when the size of the material to be heated 8 is large, or when the coil material has a low impedance, a low impedance The operation is started, and in this case, the voltage reference setter 11 of the inverter device may at least overcurrent.

FIG. 10 is a characteristic diagram showing an impedance change accompanying a change in the position of the material 8 to be heated with respect to the load coil 72 described above. 10, the position l ₀ is the position where the tip of the material to be heated 8 passes through the compression side end portion of the load coil 72, the position l ₆ is slightly before the right end portion of the rear end load coil 72 of material to be heated 8 Is a position that passes through. This position is l <l ₀ , l> l ₆ , and is the upper limit impedance at which the inverter device can operate.

On the other hand, when the position is started in the range of l ₃ <l <l ₅ , the load impedance may be lower than the lower limit impedance depending on the coil size, the coil material and the like.

[0014]

As described above,
The method of operation of the conventional inverter apparatus, is activated on the condition that the leading end of the material to be heated 8 to the load coil 72 in FIG. 10 has been inserted to the position l _2, the rear end of the material to be heated 8 position l ₆ This is a method of stopping operation when it comes.

However, since the leading end of the material to be heated 8 is located in the load coil 72 from the time of starting the heating, when uniform heating is required, insufficient heating results in a factor that deteriorates the product yield. Has become.

[0016] On the other hand, the quenching or the like which does not require an even heating of the heated material 8, there are cases that the low heating of the tip portion of the heated material 8, the operation in this case the inverter device of l ₃ in FIG. 10 Since the load is started at the position, the load impedance becomes the lower limit impedance for stable operation, and the inverter device may stop due to overcurrent.

Accordingly, an object of the present invention is to enable the operation of the inverter device without being restricted by the position of the material to be heated in the load coil, or the size and material of the material, that is, the load impedance. An object of the present invention is to provide a control device for an inverter device.

[0018]

In order to achieve the above object, a forward converter for converting AC power into DC power and a DC power converted by the forward converter are converted into high-frequency AC power. A load commutation type inverter device configured to generate an eddy current loss by high frequency magnetic flux generated from the load coil and to inductively heat a material to be heated such as a metal material. In the control device of the first aspect, the AC input current level of the inverter device after the operation of the inverter starts operation is compared with a predetermined reference current level set in advance to determine the magnitude relationship between the two. When it is determined that the AC input current level is larger than the reference current level based on the result of the discrimination by the magnitude discriminating means and the magnitude discriminating means, the control angle α of the forward converter is changed in the delay direction. If the constant control angle alpha _1, also the alternating input current level was determined to be smaller than the reference current level, the forward converter of the control angle alpha of the leading direction of the fixed control angle alpha ₂
Control means for increasing or decreasing the voltage control signal of the forward converter for a certain period of time.

Therefore, in the control device of the inverter device according to the first aspect of the present invention, the magnitude of the AC input current immediately after the start of the inverter device is determined, and the control angle α of the forward converter is set for a predetermined time in the delay direction. by fixing the fixed control angle alpha ₁ or advance direction of the fixed control angle alpha _2, starting initial impedance large, relative to the phenomenon in which small, without the interruptor or overcurrent trip, stabilize the inverter device Can be driven.

According to the second aspect of the present invention, the DC current level of the inverter device after the start of operation of the inverter is compared with a predetermined reference current level set in advance to determine the magnitude relationship between the two. When it is determined that the DC current level is greater than the reference current level based on the magnitude discrimination means and the magnitude discrimination means, the control angle α of the forward converter is changed to the fixed control angle α in the delay direction. _1, also DC when the current level is determined to be smaller than the reference current level, as a forward converter fixed control angle alpha ₂ along the advancing direction of the control angle alpha of the voltage of a predetermined time forward converter Control means for increasing or decreasing the control signal.

Therefore, in the control device of the inverter device according to the second aspect of the present invention, whether the DC current is large or small immediately after the start of the inverter device is determined, and the control angle α of the forward converter is fixed for a predetermined time in the delay direction. by fixing the fixed control angle alpha ₂ of the fixed control angle alpha ₁ or advance direction, initial start-up of the impedance is large, relative to the phenomenon in which small, without the interruptor or overcurrent trip, the inverter device stably Can drive.

Further, according to the third aspect of the present invention, the AC output current level of the inverter device after the inverter starts operating is compared with a predetermined reference current level set in advance to determine the magnitude relationship between the two. When it is determined that the AC output current level is greater than the reference current level based on the magnitude discrimination means for discriminating and the magnitude discrimination means, the control angle α of the forward converter is fixed in the delay direction. Angle α ₁ ,
Also when the AC output current level is determined to be smaller than the reference current level, as a fixed control angle alpha ₂ along the advancing direction of the alpha control angle of the forward converter, a certain time the voltage control of the forward converter Control means for increasing or decreasing the signal.

Therefore, in the control device for the inverter device according to the third aspect of the present invention, the magnitude of the AC output current immediately after the start of the inverter device is determined, and the control angle α of the forward converter is changed for a fixed time in the delay direction. by fixing the fixed control angle alpha ₁ or advance direction of the fixed control angle alpha _2, starting initial impedance large, relative to the phenomenon in which small, without the interruptor or overcurrent trip, stabilize the inverter device Can be driven.

On the other hand, according to the invention of claim 4, the above-mentioned claim 1 is provided.
4. The control device for an inverter device according to claim 1, wherein the control means does not increase or decrease the voltage control signal for a fixed time, but changes the current level to a reference level. The voltage control signal is increased or decreased so that the control angle α of the forward converter becomes the fixed control angle α ₁ in the delay direction or the fixed control angle α _{2 in the} advance direction.

Therefore, in the control device of the inverter device according to the present invention, the control angle α of the forward converter is increased or decreased until the current level immediately after the start of the inverter device matches the reference current level. The inverter device can be operated stably without current interruption or overcurrent trip in response to a phenomenon in which the impedance at the start of operation becomes large or small.

According to the fifth aspect of the present invention, the first aspect is provided.
The control device for an inverter device according to any one of claims 3 to 5, wherein the magnitude determining means compares the current level with a predetermined reference level to determine the magnitude relationship, The load impedance calculated from the detection signals of the output voltage and the current is compared with a predetermined reference impedance set in advance to determine the magnitude relationship between the two. If it is determined that the calculated load impedance is larger than the reference impedance, the control angle α of the forward converter is set to the fixed control angle α _{2 in} the leading direction, and the calculated load impedance is smaller than the reference impedance. in the when determining is such that a fixed control angle alpha ₁ direction delay the control angle alpha of the forward converter, the voltage control signal The number is increased or decreased.

Therefore, in the control device of the inverter device according to the fifth aspect of the present invention, whether the load impedance is large or small immediately after the start of the inverter device is determined, and the control angle α of the forward converter is changed for a predetermined time in the delay direction. by fixing the fixed control angle alpha ₂ of the fixed control angle alpha ₁ or advance direction, initial start-up of the impedance is large, relative to the phenomenon in which small, without the interruptor or overcurrent trip, the inverter device stably Can drive.

According to a sixth aspect of the present invention, in the control device for an inverter device according to any one of the first to third aspects of the present invention, the control means includes a preset reference value at the time of starting the inverter device. If it is determined that the current level is higher than the reference current level so that the current becomes the current, the control angle α of the forward converter is set to the fixed control angle α _{1 in the} delay direction, and the current level is higher than the reference current level. If it is determined that the small is to perform control to fixed control angle alpha ₂ along the advancing direction of the alpha control angle of the forward converter.

Therefore, in the control device of the inverter device according to the present invention, whether the current level immediately after the start of the inverter device is large or small is determined.
By controlling the control angle α of the forward converter for a certain period of time so that the reference current level at the time of small time is reached, current interruption and overcurrent trip can be prevented for the phenomenon that the impedance becomes large or small at the beginning of startup. The inverter device can be operated stably.

According to a seventh aspect of the present invention, in the control device for the inverter device according to the fifth aspect of the present invention, the control means performs an operation so as to be a preset reference current at the time of starting the inverter device. When it is determined that the load impedance is larger than the reference impedance, the control angle α of the forward converter is determined to be a fixed control angle α ₂ in the advancing direction, and the calculated load impedance is smaller than the reference impedance. case is to perform control to fixed control angle alpha ₁ direction delay the alpha control angle of the forward converter.

Therefore, in the control device of the inverter device according to the present invention, whether the load impedance is large or small immediately after the startup of the inverter device is determined, and the current level when the load impedance at the time of startup is large or small is determined. By controlling the control angle α of the forward converter for a certain period of time so that the reference current level is reached, the inverter device can be operated without causing current discontinuity or overcurrent trip in response to the phenomenon that the impedance becomes large or small at the start of startup. Can be operated stably.

[0032]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram showing a configuration example of a control device for an inverter device according to the present embodiment. The same parts as those in FIG. Here, only the different parts will be described.

In FIG. 1, an analog switch 30a which is turned on by an output from the discrimination time setting element 32 for a fixed time after the operation of the inverter 3 starts is provided at the output stage of the current conversion circuit 10.

A start-up current upper limiter 19 and a start-up current lower limiter 24 are provided as size determining means for determining whether the input current level is large or small. When the set values of the comparators are exceeded, the upper and lower flip-flops 21 and 26 are set by the outputs of the respective comparators 20 and 25, and the control angle delay setter 22 and the control angle advance setter 27 are set by these signals.
The analog switch 23 or 28 for opening and closing the output of the converter 1 is turned on, and the value of the control angle α of the forward converter 1 as the fixed control angle α ₁ in the delay direction or the fixed control angle α _{2 in the} advance direction is led to the adder 29. .

Further, flip-flops 21 and 26
_Means that the inverter 3 is reset at T _CNP after the operation by the output from the control angle change time element 31 which starts at the same time as the inverter 3 starts operating.

On the other hand, the analog switch 30 is turned on / off by an output from a control angle change time element 31 for setting a change time of the control angle α of the forward converter 1. The output from the analog switch 30 is added to the output from the lowest output voltage setting device 33 by the adder 34, and the added output is led to the high-level priority circuit 17, and the output from the voltage control regulator 13 and the current The level is compared with the output from the control adjuster 16, and the higher level is preferentially led to the phase control circuit 18.
Is controlled.

Next, the operation of the control device of the inverter device according to the present embodiment configured as described above will be described with reference to FIG.
This will be described with reference to FIG. FIG. 2 is a diagram showing the relationship between the DC current and the control angle correction period.

In FIG. 1, when the inverter device is started in a state where the material to be heated 8 is not inserted into the load coil 72 or is sufficiently inserted, when the forward converter 1 starts operating, Until the DC current rises to a certain level, the inverter 3 is operated by firing the U and X phases to form a bypass pair (hereinafter abbreviated as Bpp).

When the DC current rises to a certain level, the thyristor of the starting circuit 4 is ignited, and the charge of the capacitor of the starting circuit 4 which has been charged in advance is converted to the inverse converter 3.
And discharge to the load 7 to release the Bpp of the inverter 3 and to induce a high-frequency voltage in the parallel resonant load 7 so that the inverter 3 starts operating at a high frequency.

On the other hand, when the operation of the inverse converter 3 is started, the inverter device operates in order to smoothly start up.
Is the lowest voltage, and the voltage control signal is clipped to a value determined by the lowest voltage setter 33 so that operation can be continued at a lower output voltage.

When the inverter 3 starts operating,
The current upper limit comparator 20 and the current lower limit comparator 25, which are means for determining whether the input current is large or small at the time of starting the inverter device, use the time T _DET set by the input current large or small determination time setting element 32 at the time of startup. When the current lower limit comparator 25 operates, it is determined that the impedance is large, and the current lower limit comparator 25
, The current lower limit flip-flop 26 is set, and the analog switch 28 is turned on by the output, and the set voltage (−V _L ) of the control angle advance setter 27 is input to the adder 29.

In this case, the analog switches 23 and 2
8 is an opposing operation, and both are not turned on at the same time. Therefore, only the set voltage (−V _L ) of the control angle advance setter 27 is input to the adder 29.

The control angle change time element 31 turns on the analog switch 30 during the control angle change time T _{CNP when} the inverter 3 starts operating, and the set voltage of the control angle advance setter 27 is 34, the lowest output voltage setting device 3
Third setting voltage (+ V _MIN) and is added, (+ V _MIN -V
_L ) is the high-level priority circuit 1 as the control angle advance output.
7, the output V _AVR from the voltage control regulator 13,
The output V _ACR from the current control regulator 16 is compared with
_{Since the} level is higher than the output of either _AVR or V _ACR ,
(+ V _MIN −V _L ) is input to the phase control circuit 18 as a voltage control signal, and the control angle α of the forward converter 1 is fixed at the fixed control angle α ₂ in the leading direction.

As a result, it is possible to raise the minimum output voltage of the inverter by ΔV ₁ and increase the DC current, thereby preventing current interruption at the start of the inverter.

On the other hand, when the positional relationship between the material 8 to be heated and the load coil 72 is from l _{0 to} l ₁ , the inverter device is started, and the current lower limit comparator 25 detects the current lower limit and performs the control angle advance operation between T _CNP and T _CNP. During this time, the material to be heated 8
The escaped large impedance limit period, enters the current continuous operation period l ₂ of the inverter device.

At this point, the control angle advance operation is canceled by the control angle change time element 31, and the normal operation mode is set. On the other hand, when the input current upper limit comparator 20 operates when the inverter device is started, the flip-flop 2
1 is set, the analog switch 23 is turned on, and the set voltage (+ V _H ) of the control angle delay setter 22 is input to the adder 29.

In this case, since the analog switch 30 is turned on by the output from the control angle change time element 31,
The set voltage (+ V _H ) of the control angle delay setting unit 22 is
1 and the set voltage (+ V
_MIN ), and a voltage of (+ V _MIN + V _H ) is input to the delay priority circuit 17 as a control angle delay compensation output, and the output V _AVR from the voltage control adjuster 13 and the current control adjuster 16
Is compared with the output V _ACR from the output, and since the level is higher than any of the outputs V _AVR and V _ACR , (+ V _MIN + V _H )
Is input to the phase control circuit 18 as a voltage control signal, and the control angle α of the forward converter ₁ is fixed to the fixed control angle α ₁ in the delay direction.

As a result, the minimum output voltage of the inverter device is reduced by ΔV ₂ , the DC current is reduced, and an overcurrent at the time of starting the inverter device can be prevented. The above state will be described with reference to FIG. 10. The positional relationship between the material 8 to be heated and the load coil 72 is determined when the inverter device starts up at l _{3 to} l ₅ or when the diameter of the load coil 72 changes. If the diameter of the 8 small gap between large load coil 72 is used to vary the load impedance characteristics of Z _2, the current upper limit comparator 20 is the control angle delay operation by detecting the current limit is performed between T _CNP but , the material to be heated 8 is heated by the impedance rises during this time, passes through a l ₄ is a current stable section of the inverter device.

At this time, the analog switch 30 is turned off by the output from the control angle change time element 31, and the control angle delay operation is canceled, and the normal operation mode is set. As described above, the control device for the inverter device according to the present embodiment determines whether the AC input current is large or small immediately after the startup of the inverter device, and adjusts the control angle α of the forward converter 1 for a predetermined time in the delay direction. Since the fixed control angle α ₁ or the fixed control angle α ₂ in the leading direction is fixed, the inverter device is not interrupted or over-current tripped in response to the phenomenon that the impedance becomes large or small at the initial stage of starting. Can be operated stably.

Thus, the inverter device can be operated without being restricted by the position of the material to be heated 8 in the load coil 72 or the size and material of the material, that is, the load impedance.

(Second Embodiment) FIG. 3 is a block diagram showing a configuration example of a control device for an inverter device according to the present embodiment. The same parts as those in FIG. Are omitted, and only different portions will be described here.

FIG. 3 differs from FIG. 1 in that the current detection target at the time of starting the inverter device is a DC current instead of an AC input current. That is, the DC current is detected by the DC current transformer 35, and the detected value is converted by the DC current conversion circuit 36 into an appropriate value necessary for a circuit for determining whether the inverter is large or small when the inverter is started. Upper limit comparator 20 and current lower limit comparator 2
5.

Next, the operation of the control device of the inverter device according to the present embodiment configured as described above will be described. In FIG. 3, the DC current at the time of starting the inverter device is detected by a DC current transformer 35 and guided to a DC current conversion circuit 36, and is converted into an appropriate value for controlling the detection value of the DC current transformer 35. Then, it is input to the current upper limit comparator 20 and the current lower limit comparator 25 when the inverter device is started.

The operation thereafter is exactly the same as in the case of FIG. 1 described above, and a description thereof will be omitted here. As described above, the control device for the inverter device according to the present embodiment determines whether the DC current is large or small immediately after the startup of the inverter device, and changes the control angle α of the forward converter 1 for a certain period of time.
Since the delay direction of the fixed control angle alpha ₁ or advance to secure a fixed control angle alpha ₂ directions, starting an initial impedance large, relative to the phenomenon in which small, without the interruptor or overcurrent trip Thus, the inverter device can be operated stably.

Thus, the inverter device can be operated without being restricted by the position of the material to be heated 8 in the load coil 72 or the size and material of the material, that is, the load impedance.

(Third Embodiment) FIG. 4 is a block diagram showing a configuration example of a control device of an inverter device according to the present embodiment. The same parts as those in FIG. Are omitted, and only different portions will be described here.

FIG. 4 differs from FIG. 1 in that the current detection target at the time of starting the inverter device is an AC output current instead of an AC input current. That is, the AC output current is detected by the output current transformer 37, and the detected value is converted by the output current conversion circuit 38 into an appropriate value necessary for the large / small current discrimination circuit at the time of starting the inverter device. The configuration leads to the current upper limit comparator 20 and the current lower limit comparator 25.

Next, the operation of the control device of the inverter device according to the present embodiment configured as described above will be described. In FIG. 4, the AC output current at the time of starting the inverter device is detected by the output current transformer 37 and guided to the output current conversion circuit 38 to have an appropriate value for controlling the detection value of the output current transformer 37. The converted signal is input to the current upper limit comparator 20 and the current lower limit comparator 25 when the inverter device is started.

The operation thereafter is exactly the same as in the case of FIG. 1 described above, and a description thereof will be omitted here. As described above, the control device for the inverter device according to the present embodiment determines whether the AC output current is large or small immediately after the startup of the inverter device, and changes the control angle α of the forward converter 1 in the delay direction for a fixed time. Since the fixed control angle α ₁ or the fixed control angle α ₂ in the leading direction is fixed, the inverter device is not interrupted or over-current tripped in response to the phenomenon that the impedance becomes large or small at the initial stage of starting. Can be operated stably.

Thus, the inverter device can be operated without being restricted by the position of the material to be heated 8 in the load coil 72 or the size and material of the material, that is, the load impedance.

(Fourth Embodiment) FIG. 5 is a block diagram showing a configuration example of a control device of an inverter device according to the present embodiment, and the same parts as those in FIGS. 1, 3 and 4 are denoted by the same reference numerals. The description thereof is omitted, and only different parts will be described here.

In FIG. 5, the difference from FIGS. 1, 3, and 4 is that in FIGS. 1, 3, and 4, the voltage control signal increase / decrease period at the time of starting the inverter device is a control angle change time element 31. While the fixed time T _CNP is determined, until the current level rises or decreases until the current level matches the reference current level,
The point is that the control angle α of the forward converter 1 is increased or decreased.

That is, at the output stage of the current conversion circuit 10,
A current set value level matching circuit 40 is provided, and the current upper limit comparator 20 and the current lower limit comparator 25 operate the forward converter 1 with respect to the rated current at startup of the inverter device set by the startup current setter 39. The control angle α is increased or decreased until the current set value level matching circuit 40 operates, and when the level matches the reference current level, the current set value level coincidence is canceled so that the control angle α of the forward converter 1 is released. A signal is sent from the circuit 40 to the level matching hold circuit 46, the level matching signal is held, and the analog switch 30 is kept off until the inverter device stops.

Next, the operation of the control device of the inverter device according to the present embodiment configured as described above will be described. In FIG. 5, the operation of the current upper limit comparator 20 and the current lower limit comparator 25 causes the control angle α of the forward converter 1 to increase or decrease with respect to the rated current at startup of the inverter device set by the startup current setting device 39. This operation is performed until the current set value level matching circuit 40 operates.

[0065] That is, in this case, until the current level I is increased to reduce or reference current level I _s to the reference current level I _s, when the current level I> reference current level I _s is
Control angle alpha = the delay direction of the fixed control angle alpha ₁ of the forward converter 1, when the current level I <reference current level I _s is a control angle alpha = leading direction of the fixed control angle alpha ₂ of the forward converter 1 The control is performed as follows.

When the level matches the reference current level, the current set value level matching circuit 40 sends a signal to the level matching hold circuit 46 to cancel the increase or decrease of the control angle α of the forward converter 1, and the level matching is performed. The turning off of the analog switch 30 by holding the signal is continued until the inverter device stops.

The other operations are the same as those shown in FIG.
Since it is completely the same as the case of FIG. 3 and FIG. 4, the description is omitted here. As described above, in the control device for the inverter device according to the present embodiment, the control angle α of the forward converter 1 is increased or decreased until the current level immediately after the start of the inverter device matches the reference current level. Therefore, for the phenomenon that the impedance at the beginning of startup becomes large or small,
It is possible to stably operate the inverter device without interrupting current or tripping overcurrent.

Thus, the inverter device can be operated without being restricted by the position of the material to be heated 8 in the load coil 72 or the size and material of the material, that is, the load impedance.

(Fifth Embodiment) FIG. 5 is a block diagram showing a configuration example of a control device for an inverter device according to the present embodiment, and the same parts as those in FIGS. 1, 3 and 4 are denoted by the same reference numerals. The description thereof is omitted, and only different parts will be described here.

FIG. 5 is different from FIGS. 1, 3 and 4 in that, in FIGS. 1, 3 and 4, the control angle α of the forward converter 1 is changed to increase the current level. The difference is that while the small is determined, the magnitude of the load impedance is determined.

That is, the AC output current of the inverter device is detected by the output current transformer 37, this current signal is input to the load impedance detection circuit 41, and the voltage signal from the output voltage transformer 5 is detected by the load impedance detection circuit. 41, the load impedance is converted from the voltage signal and the current signal into an appropriate voltage signal, and the converted voltage signal is input to the impedance upper limit comparator 20a and the impedance lower limit comparator 25a. Setting device 19a and start-up impedance lower limit setting device 2
Compared with the set value (reference impedance) from 4a,
The control angle α of the forward converter 1 is increased or decreased by a control angle change time element 3
The configuration is such that only the predetermined time T _CNP determined by 1 is performed.

Next, the operation of the control device of the inverter device according to the present embodiment configured as described above will be described. In FIG. 6, an output current is detected by an output current transformer 37 and is input to a load impedance detection circuit 41 as a current signal.

Further, a voltage signal is input from output voltage transformer 5 to load impedance detection circuit 41. And
In the load impedance detection circuit 41, the square of the voltage signal / the output power is calculated from the voltage signal and the current signal,
The load impedance is converted into an appropriate voltage signal, and is input to the impedance upper limit comparator 20a and the impedance lower limit comparator 25a.

On the other hand, each of comparators 20a and 20a
In 5a, the detected load impedance is compared with the set value (reference impedance) from the starting impedance upper limit setting device 19a and the starting impedance lower limit setting device 24a.

As a result, in the case of the upper limit operation, the control angle α of the forward converter 1 is advanced (fixed to the fixed control angle α ₂ in the advance direction), and in the case of the lower limit operation, the control angle of the forward converter 1 is controlled. The α delay operation (fixed to the fixed control angle α ₁ in the delay direction) is performed only for a certain time T _CNP determined by the control angle change time element 31.

[0076] That is, in this case, when the detected load impedance Z> reference load impedance Z _s is the control angle alpha = leading direction of the fixed control angle alpha ₂ of the forward converter 1, the detected load impedance Z <reference load impedance Z _s
In this case, the control is performed such that the control angle α of the forward converter 1 is equal to the fixed control angle α _{1 in the} delay direction.

The other operations are the same as those shown in FIG.
Since it is completely the same as the case of FIG. 3 and FIG. 4, the description is omitted here. As described above, the control device for the inverter device according to the present embodiment determines whether the load impedance is large or small immediately after the start of the inverter device, and changes the control angle α of the forward converter for a certain time T _CNP and the delay direction. Fixed control angle α ₁
Alternatively, since the forward control angle is fixed to the fixed control angle α ₂ , the inverter device can be operated stably without current interruption or overcurrent trip against the phenomenon that the impedance at the start of operation becomes large or small. It becomes possible.

Thus, the inverter device can be operated without being restricted by the position of the material to be heated 8 in the load coil 72 or the size and material of the material, that is, the load impedance.

(Sixth Embodiment) FIG. 7 is a block diagram showing a configuration example of a control device of an inverter device according to the present embodiment, and the same parts as those in FIGS. 1, 3 and 4 are denoted by the same reference numerals. The description thereof is omitted, and only different parts will be described here.

7 differs from FIGS. 1, 3 and 4 in that the means for changing the control angle α of the forward converter 1 in FIGS. By discrimination,
While the control angle alpha had a constant value alpha ₁ or alpha _2, so that large and small reference current level of the current at the time of startup of the preset inverter control angle alpha, control of the forward converter 1 The point is that the angle α is controlled so that α ₁ <α <α ₂ for a certain period of time.

That is, the output from the current conversion circuit 10 and the output from the control angle delay setting unit 22 are added to the adder 4
2, the deviation is amplified by the control angle delay adjuster 43, and similarly, the output from the current conversion circuit 10 and the output from the control angle advance setter 27 are added by the adder 44, The deviation is amplified by the control angle advance adjuster 45, and the outputs from the control angle delay adjuster 43 and the control angle advance adjuster 45 are input to the analog switches 23 and 28.

Next, the operation of the control device for an inverter device according to the present embodiment configured as described above will be described. 7, the output from the current conversion circuit 10 and the output from the control angle delay setter 22 are added by an adder 42,
The deviation is amplified by the control angle delay adjuster 43.

When the current upper limit comparator 20 is operating, the analog switch 23 is turned on only for the time T _CNP during which the control angle change time element 31 is operating, so that the output from the control angle delay adjuster 43 is Analog switch 23
Is input to the adder 29 through the control angle delay setting unit 22
Is controlled so that the set current (reference current level) is obtained.

On the other hand, similarly, the output from the current conversion circuit 10 and the output from the control angle advance setting unit 27 are added by the adder 44, and the deviation is amplified by the control angle advance adjuster 45.

When the current lower limit comparator 25 is operating, the analog switch 28 is turned on during T _CNP , so that the output from the control angle advance adjuster 45 is input to the adder 29 via the analog switch 28. Then, the control angle α of the forward converter 1 is controlled so as to become the set current (reference current level) of the control angle advance setter 27.

That is, in this case, when the current level is larger than the reference current level so that the current level becomes the preset reference current level at the time of starting, the control angle α of the forward converter 1 is fixed in the delay direction. When the angle α ₁ and the current level are smaller than the reference current level, control is performed such that the control angle α of the forward converter 1 becomes the fixed control angle α _{2 in the} advancing direction.

As described above, the control device for the inverter device according to the present embodiment determines whether the current level is large or small immediately after the startup of the inverter device.
Since the control angle α of the forward converter is controlled for a fixed time so that the reference current level becomes small, the current is interrupted and an overcurrent trip is performed for the phenomenon that the impedance becomes large or small at the initial stage of starting. Without this, the inverter device can be operated stably.

Thus, the inverter device can be operated without being restricted by the position of the material to be heated 8 in the load coil 72 or the size and material of the material, that is, the load impedance.

(Seventh Embodiment) FIG. 8 is a block diagram showing a configuration example of a control device of an inverter device according to the present embodiment, and the same parts as those in FIGS. 1, 3 and 4 are denoted by the same reference numerals. The description thereof is omitted, and only different parts will be described here.

8, FIG. 3 and FIG. 4 are different from FIG. 1, FIG. 3 and FIG. 4 in that in FIG. 1, FIG. 3 and FIG. By discrimination,
While the control angle alpha had a constant value alpha ₁ or alpha _2,
The control angle α of the forward converter 1 is set to a predetermined time α ₁ <α so that the control angle α becomes a large and small reference current level of the load impedance at the time of starting the inverter device.
<In that so as to control the alpha _2.

That is, the output from the load impedance detection circuit 41 and the output from the control angle advance setting unit 22a are added by the adder 42, and the deviation is amplified by the control angle advance adjuster 45. The output from the impedance detection circuit 41 and the output from the control angle delay setting unit 27a are added by an adder 44, and the deviation is amplified by the control angle delay adjuster 43, and the control angle advance adjuster 45 and the control angle delay adjustment The output from the switch 43 is input to the analog switch 23 and the analog switch 28.

Next, the operation of the control device of the inverter device according to the present embodiment configured as described above will be described. 8, the output from the load impedance detecting circuit 41 and the output from the control angle advance setting unit 22a are added by an adder 42, and the deviation is amplified by a control angle advance adjuster 45.

The impedance upper limit comparator 2
When 0a is operating, the analog switch 23 is on for the control angle change time T _CNP , so the output from the control angle advance adjuster 45 is input to the adder 29 via the analog switch 23, The control angle α of the forward converter 1 is controlled so as to become the set current (reference current level) of the control angle advance setter 22a.

On the other hand, similarly, the output from the load impedance detection circuit 41 and the output from the control angle delay setter 27a are added by an adder 44, and the deviation is amplified by the control angle delay adjuster 43.

The impedance lower limit comparator 2
When the switch 5a is operating, the analog switch 28 is set to T _CNP
, The output from the control angle delay adjuster 43 is input to the adder 29 via the analog switch 28, and is forwarded so as to become the set current (reference current level) of the control angle delay setter 27a. The control angle α of the converter 1 is controlled.

That is, in this case, when the load impedance is larger than the reference load impedance level so that the load impedance level becomes the preset reference current level at the time of starting, the control angle α of the forward converter 1 is set.
The leading direction of the fixed control angle alpha _2, when the load impedance is less than the reference load impedance level, control is performed such that the fixed control angle alpha ₁ of the delay direction.

As described above, the control device for the inverter device according to the present embodiment determines whether the load impedance is large or small immediately after the startup of the inverter device, and compares the load impedance at startup with the reference current level when the load impedance is large or small. So that
Since the control angle α of the forward converter 1 is controlled for a fixed time, current intermittent and overcurrent trips can be prevented against the phenomenon that the impedance becomes large or small at the initial stage of starting.
The inverter device can be operated stably.

Thus, the inverter device can be operated without being restricted by the position of the material to be heated 8 in the load coil 72 or the size and material of the material, that is, the load impedance.

[0099]

As described above, according to the first to third aspects of the present invention, the AC input current level, the DC current level, or the AC level of the inverter device after the inverter starts operating. The output current level is compared with a predetermined reference current level set in advance to determine the magnitude relationship between the two. If it is determined that the current level is higher than the reference current level, the control angle of the forward converter is determined. α is a fixed control angle α ₁ in the delay direction, and if the current level is determined to be smaller than the reference current level, the control angle α of the forward converter is determined.
The voltage control signal of the forward converter is increased or decreased for a certain period of time so that the angle becomes a fixed control angle α ₂ in the advancing direction. The inverter device can be operated stably without causing a current trip, so that the position of the material to be heated in the load coil, or the size and material of the material, that is, the load impedance of the inverter device is not restricted. It is possible to provide a control device of an inverter device capable of performing an operation.

According to a fourth aspect of the present invention, in the control device for an inverter device according to any one of the first to third aspects, the current level is reduced or increased to a reference level. as a forward converter of the control angle alpha of the delay direction of the fixed control angle alpha ₁ or advance direction of the fixed control angle alpha _2, since to carry out the increase and decrease of the voltage control signal, starts the initial impedance large, small The inverter device can be operated stably without current interruption or overcurrent trip, and the position of the material to be heated in the load coil, or the size and material of the material, that is, the load A control device for an inverter device capable of operating the inverter device without being restricted by impedance can be provided.

According to a fifth aspect of the present invention, in the control device for an inverter device according to any one of the first to third aspects of the present invention, the operation is performed based on the output voltage and current detection signals of the inverter device. The calculated load impedance is compared with a predetermined reference impedance set in advance to determine the magnitude relationship between the two. If the calculated load impedance is determined to be greater than the reference impedance, the control angle of the forward converter is determined. α is a fixed control angle α ₂ in the leading direction, and if it is determined that the calculated load impedance is smaller than the reference impedance, the control angle α of the forward converter is set to the fixed control angle α _{1 in the} lag direction. To
Since the voltage control signal is increased or decreased, the inverter device can be operated stably without intermittent current or overcurrent trip against the phenomenon that the impedance at the start of operation becomes large or small. It is possible to provide a control device for an inverter device capable of operating the inverter device without being restricted by the position of the material to be heated in the coil or the size and material of the material, that is, the load impedance.

According to a sixth aspect of the present invention, in the inverter device control apparatus according to any one of the first to third aspects, the reference current at the time of starting the inverter device and the preset reference current are set. So that when it is determined that the current level is higher than the reference current level,
If the control angle α of the forward converter is determined to be the fixed control angle α ₁ in the delay direction, and if the current level is determined to be smaller than the reference current level, the control angle α of the forward converter is changed to the fixed control angle α in the forward direction. since to carry out control to alpha _2, starting initial impedance large, relative to the phenomenon in which small, without the interruptor or overcurrent trip, the inverter device can be operated stably, with the load coil It is possible to provide a control device for an inverter device capable of operating the inverter device without being restricted by the position of the material to be heated or the size or material of the material, that is, the load impedance.

According to the seventh aspect of the present invention, the load impedance calculated by the control device for the inverter device according to the fifth aspect of the present invention is set so as to be a preset reference current at the time of starting the inverter device. If it is determined that the impedance is larger than the impedance, the control angle α of the forward converter is a fixed control angle α _{2 in} the leading direction, and if it is determined that the calculated load impedance is smaller than the reference impedance, since to carry out control to fixed control angle alpha ₁ direction delay the control angle alpha of the forward converter, with respect to the phenomenon of activation initial impedance large, becomes small,
The inverter device can be operated stably without interrupting current or overcurrent trip, so that there is no restriction on the position of the material to be heated in the load coil, or the size and material of the material, that is, the load impedance. In addition, it is possible to provide a control device for an inverter device capable of operating the inverter device.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of a control device for an inverter device according to the present invention.
FIG. 2 is a block diagram showing an embodiment.

FIG. 2 is a diagram showing a relationship between a DC current and a control angle correction period in the control device of the inverter device according to the present invention.

FIG. 3 shows a second embodiment of the control device of the inverter device according to the present invention.
FIG. 2 is a block diagram showing an embodiment.

FIG. 4 shows a third control device of the inverter device according to the present invention.
FIG. 2 is a block diagram showing an embodiment.

FIG. 5 shows a fourth control device of the inverter device according to the present invention.
FIG. 2 is a block diagram showing an embodiment.

FIG. 6 shows a fifth embodiment of the control device of the inverter device according to the present invention.
FIG. 2 is a block diagram showing an embodiment.

FIG. 7 shows a sixth embodiment of the control device of the inverter device according to the present invention.
FIG. 2 is a block diagram showing an embodiment.

FIG. 8 shows a seventh embodiment of the control device for the inverter device according to the present invention.
FIG. 2 is a block diagram showing an embodiment.

FIG. 9 is a block diagram showing a configuration example of a control device for an inverter device according to a conventional technique.

FIG. 10 is a characteristic diagram showing a change in impedance according to a change in the position of a material to be heated.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Forward converter, 2 ... DC reactor, 3 ... Inverter converter, 4 ... Start-up circuit, 5 ... Output voltage transformer, 6 ... Input current transformer, 7 ... Parallel resonant load, 71 ... Power factor improvement capacitor, 72 ... load coil, 8 ... material to be heated, 9 ... voltage conversion circuit, 10 ... current conversion circuit, 11 ... voltage reference setter, 12, 15, 29, 34, 42, 44 ... adder, 13 ... voltage control regulator Reference numeral 14: Current reference setter 16: Current control adjuster 17: High-level priority circuit 18: Phase control circuit 19: Start-up current upper limiter 19a: Start-up impedance upper limiter 20: Current upper limit Comparator, 20a: Impedance upper limit comparator, 21a: Impedance upper limit flip-flop, 22: Control angle delay setter, 23, 28, 30, 30a: Analog switch, 24 ... Operating current lower limit setting device, 24a: Starting impedance lower limit setting device, 25: Current lower limit comparator, 25a: Impedance lower limit comparator, 26: Current lower limit flip-flop, 26a: Impedance lower limit flip-flop, 27: Control angle advance setting device, 31: control angle change time element, 32: discrimination time setting element, 33: minimum output voltage setter, 35: DC current transformer, 36: DC current converter, 37: output current transformer, 38: output current converter 39, a current setting device at start-up, 40, a current set value level matching circuit, 41, a load impedance detection circuit, 43, a control delay adjuster, 45, a control lead adjuster, 46, a level match hold circuit.

Claims (7)

[Claims] 1. A forward converter for converting AC power into DC power, and an inverter for converting DC power converted by the forward converter into high-frequency AC power and supplying the AC power to a load coil, In a control device of a load commutation type inverter device used to generate an eddy current loss with a high-frequency magnetic flux generated from the load coil and induction-heat a material to be heated such as a metal material, the inverter operates. A magnitude discriminating means for comparing the AC input current level of the inverter device from the start with a predetermined reference current level set in advance and discriminating a magnitude relation between the two, based on a discrimination result by the magnitude discriminating means. If it is determined that the AC input current level is higher than the reference current level, the control angle α of the forward converter is set to a fixed control angle α _{1 in the} delay direction, and the AC input current level If Le is determined to be smaller than the reference current level, so that the forward converter fixed control angle alpha ₂ along the advancing direction of the control angle alpha of the voltage control signal for a predetermined time the forward converter A control device for an inverter device, comprising: control means for increasing and decreasing. 2. A forward converter for converting AC power into DC power, and an inverter for converting DC power converted by the forward converter into high-frequency AC power and supplying the AC power to a load coil, In a control device of a load commutation type inverter device used to generate an eddy current loss with a high-frequency magnetic flux generated from the load coil and induction-heat a material to be heated such as a metal material, the inverter operates. A magnitude discriminating means for comparing the DC current level of the inverter device from the start with a predetermined reference current level set in advance and discriminating a magnitude relationship between the two, based on a discrimination result by the magnitude discriminating means, When it is determined that the DC current level is larger than the reference current level, the control angle α of the forward converter is changed to the fixed control angle α _{1 in the} delay direction, and the DC current level is set to the reference current level. Control means for increasing or decreasing the voltage control signal of the forward converter for a certain period of time so that the control angle α of the forward converter becomes a fixed control angle α ₂ in the advancing direction when it is determined to be smaller than the level. A control device for an inverter device, comprising: 3. A forward converter for converting AC power to DC power, and an inverter for converting DC power converted by the forward converter to high-frequency AC power and supplying the AC power to a load coil, In a control device of a load commutation type inverter device used to generate an eddy current loss with a high-frequency magnetic flux generated from the load coil and induction-heat a material to be heated such as a metal material, the inverter operates. An AC output current level of the inverter device from the start is compared with a predetermined reference current level set in advance to determine a magnitude relationship between the two, and based on a result of the determination by the size determination means. When it is determined that the AC output current level is larger than the reference current level, the control angle α of the forward converter is changed to the fixed control angle α _{1 in the} delay direction, and the AC output current level If Le is determined to be smaller than the reference current level, so that the forward converter fixed control angle alpha ₂ along the advancing direction of the control angle alpha of the voltage control signal for a predetermined time the forward converter A control device for an inverter device, comprising: control means for increasing and decreasing. 4. The method according to claim 1, wherein
The control device for an inverter device according to any one of claims 1 to 3, wherein, as the control unit, instead of increasing or decreasing the voltage control signal only for the predetermined time, the forward converter is used until the current level decreases or increases to a reference level. Fixed angle α in the delay direction
₁ or advance as a fixed control angle alpha ₂ of the direction control device of the inverter device is characterized in that to carry out the increase and decrease of the voltage control signal. 5. The method according to claim 1, wherein
The control device for an inverter device according to Item, wherein, as the magnitude discriminating means, the magnitude of the output voltage and the current of the inverter device are compared with the magnitude of the current by comparing the current level with a predetermined reference level. The load impedance calculated from the detection signal is compared with a predetermined reference impedance level set in advance to determine the magnitude relationship between the two, and the control means is configured to determine the magnitude relationship between the two based on the determination result by the magnitude determination means. If it is determined that the calculated load impedance is larger than the reference impedance level, the control angle α of the forward converter is set to a fixed control angle α _{2 in} the leading direction, and the calculated load impedance is set to the reference impedance level. If the control angle α is determined to be smaller, the control angle α of the forward converter is fixed in the delay direction. Your angle α
A control device for an inverter device, wherein the voltage control signal is increased or decreased so as to be ₁ . 6. The method according to claim 1, wherein
In the inverter device control device according to the paragraph, as the control means, when it is determined that the current level is higher than the reference current level so as to be a preset reference current at the time of the start of the inverter device Is
The control angle α of the forward converter is a fixed control angle α ₁ in the delay direction,
An inverter characterized in that, when it is determined that the current level is smaller than a reference current level, the control angle α of the forward converter is controlled to a fixed control angle α ₂ in the leading direction. Equipment control device. 7. The control device for an inverter device according to claim 5, wherein the calculated load impedance is a reference impedance level so that the control current becomes a preset reference current at the time of starting the inverter device. When it is determined that the load angle is larger than the control angle α of the forward converter, the fixed control angle α ₂ in the advancing direction, and when it is determined that the calculated load impedance is smaller than the reference impedance level. the control device of the inverter device is characterized in that to perform the control in the forward converter direction of the fixed control angle alpha ₁ delay control angle alpha of.