JPH0783547B2 - Inverter generator - Google Patents

Description

TECHNICAL FIELD The present invention relates to an inverter-type generator that rectifies an AC output of an AC generator and then converts the AC output into an AC of an arbitrary frequency and outputs the AC.

2. Description of the Related Art Conventionally, as a portable generator that obtains an AC output at a commercial frequency, for example, a combination of a small engine and a generator is known. When adjusting the output frequency to the commercial frequency in this portable generator, it is necessary to stabilize the engine speed in a relatively low range, the operating efficiency of the engine is poor, and the engine speed changes due to load fluctuations or engine pulsation. Fluctuates easily, so it is difficult to keep the output frequency constant, and the generator must be increased. Therefore, the engine is operated in a high rotation speed range, and the output of the generator is once converted to direct current, and then converted to alternating current of an arbitrary frequency by the inverter and then output. 59-1323
No. 98 or JP-A-60-82098. In this inverter type generator, the inverter at the output stage is composed of semiconductor switching elements such as transistors, and it is necessary to provide a circuit for protecting this semiconductor element from overcurrent.

However, in the conventional inverter type generator,
When detecting and protecting the inverter overcurrent status, the operation setting value of overcurrent protection is fixedly set according to the allowable rated output, so the inverter is reliably protected by following changes in the engine speed. However, when changing the rated output by enabling the engine speed, an external changeover switch or the like is required, which complicates the configuration, and requires switch changeover operation, resulting in poor operability. It has become a thing.

The present invention has been made in consideration of the above points, and automatically changes the operation set value (reference value) of the overcurrent protection of the inverter in accordance with the change of the set value of the rated output, and at the same time, drives the drive. The setting value for overcurrent protection does not fluctuate due to fluctuations in the set engine speed or variations in the output characteristics of the alternator itself.
Even when changing the rated output of the alternator, the inverter can be reliably and stably protected from overcurrent without the need for an external switch for switching the rated output as in the past. The present invention provides an inverter generator.

Configuration To achieve the object, in the present invention, an inverter generator that exchanges a rectified output in a main output winding of an AC generator with an AC output having an arbitrary frequency through an inverter that commutates according to a drive signal. In, an overcurrent detection means for detecting the overcurrent state of the inverter by comparing the detected value of the current flowing through the inverter with a reference value, and shutting off the drive signal at the time of detecting the overcurrent state to render the inverter inoperative. Inverter protection means, a signal based on the voltage that changes according to the rectified output in the auxiliary output winding of the alternator and a signal based on the voltage that stabilizes the rectified output in the auxiliary output winding A reference value automatic setting means for setting the reference value while making a selection accordingly is provided.

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a circuit configuration of an inverter type generator according to the present invention. In the figure, 1 is an AC generator driven by an engine or the like, has an auxiliary winding L ₂ of the output winding L ₁ and the control for outputting a three-phase alternating current, three-phase output winding L ₁ The AC output is full-wave rectified by a three-phase rectifier circuit 2 composed of a thyristor bridge, and then given to a bridge type inverter 3 composed of power transistors. The single-phase AC output of the auxiliary winding L ₂ is rectified by the rectifier circuit 4 and then stabilized by the constant voltage circuit 5, and the oscillator 7 that drives the inverter 3 and the driver 7 that includes the drive transistors Q ₁ and Q _2. Given to. A constant voltage control circuit 8 having a comparator CMP is provided on the output side of the constant voltage circuit 5, and detects the fluctuation of the generator output voltage to control the conduction angle of each thyristor in the three-phase rectifier circuit 2. The rectified output is held at a constant voltage level. Specifically, the output voltage of the three-phase rectifier circuit 2 is compared with a reference voltage preset by the comparator CMP, and the conduction angle of each thyristor is controlled so that the output voltage becomes equal to the set voltage. Here, the control system is provided separately from the main circuit system as described above, so that the control system is not hindered even if the output voltage of the generator 1 decreases.

The output stage inverter 3 is controlled according to the drive signals from the drive transistors Q ₁ and Q ₂ in the driver 7,
Exchange the input DC with AC of arbitrary frequency. These drive transistors Q ₁ and Q ₂ are respectively output by the output pulse train signal of the oscillator 6 and the output of the operational amplifier OPA1 in the inverter protection circuit 9 according to the output frequency of the oscillator 6, for example, pulse signals are alternately output at the commercial frequency. Switching is controlled. That is, the drive transistor
The bases of Q ₁ and Q ₂ are respectively connected to the output side of OR gates OR1 and OR2 that form the protection circuit of the inverter 3 via resistors R ₁ and R _2, and one input side of each OR gate OR1 and OR2 is The oscillator 6 and the other input side are respectively connected to the output side of the operational amplifier OPA1. A resistance (shunt) R ₃ for current detection is provided on the DC bus to which the DC current is supplied to the inverter 3. Both ends of this resistance R ₃ are connected via resistances R ₄ and R ₅ , respectively. It is connected to the inverting input side (-) and the non-inverting input side (+) of the operational amplifier OPA1. Further, the resistors R ₄ and R ₅ are connected in series with resistors R ₆ and R ₇ , respectively, and the diode D ₁ is connected in parallel with the series circuit of the resistors R ₅ and R ₇ , and these parallel circuits are connected. Capacitors in series
C ₁ is connected.

Further, an operational amplifier OPA2 is provided as overcurrent detecting means together with the operational amplifier 8, and its inverting input side is a resistor.
It is connected to the latter stage side of the resistor R ₃ via R ₈ , and the non-inverting input side is connected to the above-described DC bus via the resistor R ₉ . Further, capacitors C ₂ and C ₃ are provided between these input side and the DC bus. And the resistance R
_A resistor R ₁₀ is connected in series with the resistor _8, and the other end of the resistor R ₁₀ together with the resistor R ₆ is a smoothing capacitor for the rectifier circuit 4.
Connected to C ₀ .

The output side of the operational amplifier OPA2 has a resistor R ₁₁ and a capacitor C ₅
Are connected in series, and the connection point is connected to the non-inverting input side of the operational amplifier OPA3. Inverting input of the operational amplifier extinguishing OPA3 is connected via a resistor R ₁₂ and the DC mother ship, resistor R ₁₂ in series to resistor R ₁₃ is connected. Further, the output of the operational amplifier OPA3 the resistance R ₁₄ via which is connected to the noninverting input of the operational amplifier OPA1, further non-inverting input side and the output side of the operational amplifier OPA1 resistance R of the operational amplifier OPA2 Connected through ₁₅ .

Next, the operation will be described. The output of the AC generator 1 is converted to DC by the three-phase rectifier circuit 2 as described above, and then input to the inverter 3. Then, the inverter 3 converts again into an alternating current of a predetermined frequency according to the drive signal given through the drive transistors Q ₁ and Q ₂ in the driver 7, and the exchanged alternating current output is supplied to the load LD such as a motor and an incandescent bulb. . At that time, the drive transistors Q ₁ , Q ₂
Is turned on (ON) and turned off (OF
F) is alternately repeated, and each power transistor of the inverter 3 is switching-controlled along with this, and an AC output with a desired voltage and frequency is obtained. Further, the current Ia flowing through the inverter 3 appears as a voltage drop across the resistor R ₃ , and when this voltage value exceeds the set value, that is, when the current value flowing through the inverter 3 exceeds the set value, an overcurrent state occurs. Immediately, the drive signal to the inverter 3 is stopped by the signal from the operational amplifier OPA1 for a predetermined time by the charging timer of the capacitor C ₁ , and the inverter 3 is protected.

At that time, the operational amplifier OPA2 detects the overcurrent state of the inverter 3 together with the operational amplifier OPA1, but the operational amplifier OPA1 detects the peak value in response to the rising of the energization current of the inverter 3, whereas the operational amplifier OPA1 detects the peak value. OPA2 is capacitor C ₂
The average value of the energizing current averaged in is detected. Then, the operational amplifiers OPA1 and OPA2 have their respective detection values (voltage values).
Is compared with a reference value (a voltage value divided by resistors R ₉ , R ₆ and resistors R ₈ , R ₁₀ ), and if the detected value exceeds the set value, it is determined as an overcurrent state. When this overcurrent state is detected, the inverter 3 is stopped by the output from the operational amplifier OPA1 in any case as described above. That is, when the output current Io to the load LD increases, the current Ia flowing through the resistor R ₃ also increases,
When this current value exceeds a predetermined value, the output of the operational amplifier OPA1 is inverted and becomes a high level signal.
OR1, the output of OR2 is driving transistor Q _1, Q ₂ are both turned off in the driver 7 becomes the high level continuously. At this time, since the capacitor C ₁ and the diode D ₁ are connected to the output side of the operational amplifier OPA1, if the peak current causes an overcurrent and the output stops, a predetermined time (charging time of the capacitor C ₁ ) After that, the inverter operation is restarted. Therefore, even if the load LD has a large inrush current, it can be reliably started. The operational amplifier OPA2
Since the resistor R ₁₁ and capacitor C ₄ are connected to the output side of
Never average current inverter operation even if an overcurrent is stopped immediately, during the time determined by the time constant of the resistor R ₁₁ and capacitor C _4, the inverter operation is continued, the charging by Condesa C ₄ Stopped after timer time. Since this stopped state is continued by the closed loop of OPA2 → OPA3 → OPA1 → OPA2, it cannot be automatically restored, and it functions as if it were an NFB (no-fuse breaker) function. Furthermore, when the peak current becomes an overcurrent and the inverter operation is stopped for a predetermined time by the output of the operational amplifier OPA1, the output signal of this operational amplifier OPA1 is input to the non-inverting input of the operational amplifier OPA2 via the resistor R _15. It is input to the terminal and stored in the capacitor C ₃ . Therefore becomes much charge storage amount of the capacitor C ₃ by the output signal from the operational amplifier OPA1 indicating the presence of a peak current, regardless of the overcurrent state of the average current to operate the operational amplifier OPA2, the average current over As with the current state, the inverter operation is stopped so that it cannot be automatically restored.

According to the present invention, in particular, according to the comparison result of the signal based on the voltage that changes according to the rectified output of the rectifier circuit 4 and the signal based on the voltage obtained by stabilizing the rectified output by the constant voltage circuit 5. Then, the reference value automatic setting including the resistors R ₁₆ and R ₁₇ and the diodes D ₂ and D ₃ that gradually changes the reference setting values of the operational amplifiers OPA1 and OPA2 in the inverter protection circuit 9 according to the setting change of the rated output. The circuit 10 is provided.

Now, the terminal voltage Vc of the capacitor C ₀ in the rectifier circuit 4
As shown in FIG. 2, becomes a voltage proportional to the rotation speed of the driving engine of the AC generator 1. Therefore, for example, when the load LD is small, the rotational speed of the drive engine should be set lower.
Rated output 150W when set to 3,000 rpm (silent mode)
When the load LD is large and the engine speed for driving is set to a higher 4,500 rpm (power mode) to obtain the rated output of 300 W, the change in the engine speed setting value at that time, In order to change the reference set value for overcurrent detection in the inverter protection circuit 9 by following the change in the rated output of the alternator 1, operational amplifiers OPA1 and OPA are provided.
The resistors R ₆ and R ₁₀ on the reference input side of 2 are both connected to the constant voltage circuit 5
It is conceivable that the reference voltage of each operational amplifier OPA1, OPA2 is obtained from the capacitor C ₀ in the rectifier circuit 4 by connecting to the output side of the rectifier circuit 4 without going through.

However, in that case, if the engine speed is not stable,
The reference set value for overcurrent detection fluctuates, and the operation of the overcurrent protection of the inverter 3 becomes unstable. Further, since the output voltage is responsive to the voltage, the variation of the output voltage based on the performance of the AC generator 1 has a great influence, and the operation of the overcurrent protection becomes unstable.

In the present invention, however, the automatic reference value setting circuit 10 is provided between the rectifier circuit 4 and the constant voltage circuit 5, so that it is not affected by fluctuations in engine speed and variations in generator output characteristics. It is possible to automatically and optimally set the reference value for detecting the overcurrent of the inverter protection circuit 9 in accordance with the change of the setting of the rated output to stably perform the overcurrent protection of the inverter 3.

That is, the operational amplifier OP in the inverter protection circuit 9
The reference set value for overcurrent detection set in each of A1 and OPA2 is proportional to the voltage V _B applied to the voltage dividing resistors R ₆ and R ₄ and R ₁₀ and R ₈ on the reference input side.

At that time, in the region where the engine speed is 0 to N _{1 while} the output voltage of the constant voltage circuit 5 gradually increases after the engine for driving the AC generator 1 is started, the current is the first It flows through the route of a in the figure, and then V _B is given by the following equation (1).

Here, Vc is a terminal voltage of the capacitor C ₀ in the rectifying circuit 4, and has a value that changes in proportion to the engine speed. Therefore, in the range of the engine speed 0 to N ₁ , the reference set value for overcurrent detection changes according to the engine speed.

Further, the engine speed N is maintained while the output voltage of the constant voltage circuit 5 is stabilized to a constant value E and the potential at the voltage dividing point of the resistors R ₁₆ and R ₁₇ is lower than the output voltage E of the constant voltage circuit 5. _{From 1}
In the region of N ₂ (for example, the rated speed of 3,000 rpm in the silent mode mentioned above is included in this region), the current flows through the route of a in FIG. 1, at which time V _B is expressed by the following equation (2).
Given by.

Therefore, in the engine speed range from N ₁ to N ₂ , the reference set value for overcurrent detection is always kept constant regardless of the engine speed.

Further, the engine speed increases and the potential at the voltage dividing point of the resistors R ₁₆ and R ₁₇ is higher than the output voltage E of the constant voltage circuit 5, but the resistor R ₁₇
In the region of engine speed N ₂ to N _{3 while} the potential of the voltage dividing point between the resistor and the resistor R ₁₀ or R ₆ is lower than the output voltage E of the constant voltage circuit 5, the current flows through the route of B in FIG. ,then
V _B is given by the following equation (3).

Therefore, in the range of engine speeds N ₂ to N ₃ , the reference set value for overcurrent detection changes according to the engine speed.

When the engine speed further increases, the potential at the voltage dividing point between the resistance R ₁₇ and the resistance R ₁₀ or R ₆ is higher than the output voltage E of the constant voltage rotation 5 and is in the engine speed N ₃ or higher region (for example, the power mentioned above). At a rated speed of 4,500 rpm in the mode is included in this range), V _B is given by the following equation (4).

V _B = E (4) However, the voltage drop of the diode D ₃ is ignored here. Therefore, in the region where the engine speed is N ₃ or higher, the reference set value for overcurrent detection is always held constant regardless of the engine speed.

The characteristic of the reference set value for overcurrent detection according to the engine speed at this time is as shown in FIG.

In this way, the reference value automatic setting circuit 10 automatically sets the reference value for detecting the overcurrent in the inverter protection circuit 9, so that the start-up of the engine starts (in the range of 0 to N ₁ ) and the rated speed of the engine. The reference set value for overcurrent detection fluctuates according to the engine speed at the start-up by switching (N _{2 to} N ₃ range), but the engine speed is within the rated engine speed N ₁ to N ₂ range or In the range of N ₃ or more, even if the engine speed exceeds the rating and fluctuates a little, the reference set value for overcurrent detection is fixed, so that stable overcurrent protection of the inverter 3 can always be performed. Become. Also, just alternator N ₁ even if there are variations in the output characteristics of 1, N _2, N ₃ points is changed in the same direction, the allowable range of the reference set value of the overcurrent detection does not vary with respect to the variation Therefore, mass productivity is improved.

In the embodiment described above, the case where the rating is switched to two stages has been described. However, even when the number of stages for switching the rating is increased, it is easy to add a resistor and a diode by the ladder configuration in the automatic reference value setting circuit 10. Can handle.

Effects As described above, in the inverter generator according to the present invention, when switching the rated output of the inverter stepwise according to the output of the AC generator, without any external switch or the like unlike the conventional case, It is possible to automatically and reliably switch the operation set value of the inverter overcurrent protection, and to maintain a constant value without being affected by fluctuations in the rotational speed of the drive engine or variations in the output characteristics of the alternator. It has an excellent advantage that the overcurrent protection of the inverter can be stably performed with the reference set value.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electric circuit diagram showing an embodiment of an inverter generator according to the present invention, FIG. 2 is a characteristic diagram of the output voltage of a rectifier circuit with respect to the engine speed in the embodiment, FIG. FIG. 3 is a characteristic diagram of the reference set value for overcurrent detection with respect to the engine speed in the embodiment. 1 ... AC generator, 2 ... Three-phase rectifier circuit, 3 ... Inverter, 4 ... Rectifier circuit, 5 ... Constant voltage circuit, 6 ... Oscillator, 7 ... Driver, 8 ... Constant voltage control circuit , 9 ... Inverter protection circuit, 10 ... Automatic reference value setting circuit

Claims (1)

[Claims] 1. An inverter-type generator for converting a rectified output in a main output winding of an AC generator into an AC output having an arbitrary frequency through an inverter commutating according to a drive signal, and a current supplied to the inverter. An overcurrent detection unit that detects the overcurrent state of the inverter by comparing the detection value of the above with a reference value, an inverter protection unit that shuts off the drive signal when the overcurrent state is detected, and renders the inverter inoperative. While selecting a signal based on the voltage that changes according to the rectified output in the auxiliary output winding of the generator and a signal based on the voltage that stabilizes the rectified output in the auxiliary output winding according to the rotation state of the generator, An inverter-type generator characterized in that a reference value automatic setting means for setting a reference value is provided.