JPH08168220A - Engine-driven generator system - Google Patents

Abstract

PURPOSE: To provide an engine-driven generator system which can drive a load which has a large starting current such as an induction motor without increasing the size of a synchronous generator. CONSTITUTION: Field current is supplied to a field coil 3 from an exciter coil 1 through a rectifier Rec1 and a switch for controlling field current 7. A generator for excitation 10 which is driven by an angine is installed and output current of the generator for excitation 10 is overlapped on the field current through a rectifier for rectifying the output of an exciter Rec2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine-driven power generator using a synchronous generator.

[0002]

2. Description of the Related Art A synchronous generator driven by an engine (internal combustion engine) is used, for example, at a construction site to drive a device using an induction motor. As a generator of this type, a salient pole self-excited three-phase AC synchronous generator is mainly used in terms of cost.

FIG. 4 shows the structure of a conventional engine-driven power generator. In FIG. 4, 1 is an exciter coil,
Reference numeral 2 is a three-phase star-connected armature coil, and 3 is a field coil. Exciter coil 1 and 3-phase armature coil 2
u to 2w are wound around slots provided in the stator core, and three-phase output terminals 4u to 4w are derived from terminals on the side opposite to the neutral point of the armature coils 2u to 2w. The field coil 3 is concentratedly wound on salient poles provided on the rotor core, and both ends of the field coil 3 are slip rings 5
It is connected to a and 5b. Slip rings 5a, 5b
Brushes 6a and 6b are respectively brought into contact with.
In this type of generator, a permanent magnet for initial excitation is attached to the rotor core, and a voltage is induced in the exciter coil by the magnetic flux generated from the permanent magnet at the time of starting. The rotating shaft of the rotor is connected to the crankshaft of the engine via a power transmission means such as a belt.

One end and the other end of the exciter coil 1 are connected to the input terminals of the exciter output rectifier Rec1 and the smoothing capacitor C1 is connected between the output terminals of the rectifier Rec1. The exciter output rectifier Rec1 is a well-known full-wave rectifier configured by connecting diodes in a bridge connection. The positive output terminal of the rectifier Rec1 is connected to one end of the field coil 3 through the brush 6a and the slip ring 5a. It is connected. The emitter of the NPN transistor TR1 forming the field current control switch 7 is connected to the negative output terminal of the exciter output rectifier 7, and the collector of the transistor TR1 is connected to the field coil 3 through the brush 6b and the slip ring 5b.
Is connected to the other end of. A flywheel diode D1 is connected between the brushes 6a and 6b to flow a current through the field coil 3 when the current flowing through the field coil 3 is cut off. The flywheel diode D1 is connected to the rectifier Rec1 and a capacitor. A field current supply circuit 8 for supplying a field current to the field coil 3 through the rectifier Rec1 and the field current control switch 7 by the output current of the exciter coil 1 is constituted by C1, the transistor TR1, and the diode D1. There is.

In order to detect the output voltage of the generator, the input terminal of the full-wave rectifier Reco for detecting the output voltage is connected to the output terminal of the one-phase armature coil 2u and the neutral point.
A resistance voltage divider circuit consisting of a series circuit of resistors R1 and R2 is connected between the output terminals of eco. A capacitor C2 is connected between the output terminals (both ends of the resistor R2) of this voltage dividing circuit,
The voltage detection signal obtained across the capacitor C2 passes through the Zener diode ZD1 and the NPN transistor TR2.
Is applied between the base and the emitter. The emitter of the transistor TR2 is commonly connected to the emitter of the transistor TR1, and the collector of the transistor TR2 is connected to the base of the transistor TR1 and also connected to the positive output terminal of the exciter output rectifier Rec1 through the resistor R3. A resistor R4 and a capacitor C3 are connected between the base and emitter of the transistor TR2, respectively.

In this example, a rectifier Reco, a resistance voltage dividing circuit composed of resistors R1 and R2, and a capacitor C2
An output voltage detection circuit for detecting the output voltage of the generator is configured, and the Zener diode ZD1, the transistor TR2, the resistors R3 and R4, and the capacitor C3 are used for controlling the field current when the output voltage of the generator is less than the set value. Keep the switch 7 in the ON state and apply the field current to the field coil 3,
An output voltage control circuit 9 is configured to shut off the field current by turning off the field current control switch 7 when the output voltage of the generator exceeds a set value.

When the power generator is started, a voltage is induced in the exciter coil 1 and the armature coil 2 by the permanent magnet for initial excitation attached to the rotor. Initially, the output voltage of the armature coil 2 is below the set value, so
The Zener diode ZD1 is cut off and the transistor TR2 is kept off. At this time, since the base current is supplied from the exciter coil 1 to the transistor TR1 through the rectifier Rec1 and the resistor R3, the transistor TR1 becomes conductive, and the exciter coil 1 causes the rectifier Rec1, the transistor TR1 (field current control switch) and the brush. 6a, 6b and slip ring 5a,
A field current is applied to the field coil 3 through 5b.
As a result, the rotor core is excited and the voltage of the armature coil 2 is established. When the output voltage of the armature coil 2 exceeds the set value, the Zener diode ZD1 becomes conductive, and the base current is given to the transistor TR2, so that the transistor TR2 is turned on and the transistor TR2 is turned on.
1 goes off. Therefore, the field current is cut off and the voltage induced in the armature coil 2 is reduced. When the output voltage of the armature coil 2 falls below the set value, the transistor TR1 is turned off.
Are conducted, and a field current is supplied to the field coil 3. By repeating these operations, the voltage induced in the armature coil 2 is maintained at a substantially set value.

Generally, the self-excited synchronous generator has a feature that a large short-time overload output can be obtained.
The output characteristic is a characteristic accompanied by the entrainment phenomenon, as shown by the curves A and B in FIG. In FIG. 2, the vertical axis and the horizontal axis respectively show the output voltage E and the output current I of the generator, and the curve B shown by the chain line in the figure is from the synchronous generator having the characteristics of the curve A shown by the solid line. Also shows the characteristics of the synchronous generator with improved excitation characteristics. The arrows shown along the curve show the changes in the output voltage and current from the time of startup. Note that Io represents a current generated by the permanent magnet for initial excitation.

As indicated by the curves A and B in FIG. 2, the output characteristic of the self-excited synchronous generator is a characteristic in which the output is reduced due to entanglement from the maximum output point. In particular, in the case of a three-phase synchronous generator, a demagnetizing field due to an armature reaction at the time of load occurs over the entire circumference of the stator, so that the entrainment phenomenon occurs particularly remarkably.

In the synchronous generator in which the output entrainment phenomenon occurs as described above, it is necessary to allow the output to have a margin in order to drive the load, and the rated output is considerably larger than the rated power consumption of the load. It is necessary to have.
In particular, when the load is an induction motor, a current several times the rated current flows at startup, so the voltage and current required for startup can be maintained unless there is a sufficient margin in the rated output of the generator. It runs out and fails to start.

For example, as shown in FIG. 2, the rated operating point is a, the load impedance straight line at startup is RM1, and the minimum operating point for maintaining startup is b (starting minimum maintenance voltage Em, starting minimum Considering a case where an induction motor having a sustaining current Im) is used as a load of a synchronous generator having the characteristic of curve a, the generator operates at the intersection point c between the load impedance straight line RM1 and the curve a in FIG. Therefore, the minimum voltage Em and the current Im necessary for starting cannot be maintained, and the electric motor cannot be started. FIG. 3 (A) shows the actual measurement results of the temporal changes in the effective values of the output voltage E and the output current I of the generator in this case. As shown in the figure, when the induction motor is turned on at the time t1, the current I flows due to the influence of the transient reactance immediately after the turning on, but the current at the starting point cannot be maintained, and the output is finally output. The voltage E and the current I become almost zero.

Therefore, conventionally, by increasing the output of the exciter coil of the synchronous generator, the output characteristic as shown by the curve B in FIG. 2 is provided, and the operating point at the time of starting the induction motor is changed to the curve B. By setting the point d to the load impedance straight line RM1 of, the starting voltage and the starting current larger than the starting minimum sustaining voltage Em and the starting minimum sustaining current Im are obtained.

On the other hand, as a synchronous generator driven by an engine, a magnet generator is provided as an exciting generator,
A separately excited synchronous generator in which a field current is supplied from the exciting generator to a field coil is also used, and the output characteristic of the separately excited synchronous generator is as shown by a curve C in FIG. Become. According to this separately-excited synchronous generator, the point of intersection with the load impedance straight line RM1 at the time of starting the induction motor is e, and a starting voltage and current larger than the starting minimum maintaining voltage Em and the starting minimum maintaining current Im are relatively easy. Can be obtained.

[0014]

As described above, when a self-excited synchronous generator is used as a generator driven by an engine, a load that requires a large starting current, such as an induction motor, is driven. Therefore, it is necessary to have a considerable margin in the output of the generator, but in order to have a margin in the output of the generator, it is necessary to increase the output of the exciter coil, so low speed operation At times, the field current increased and there was a risk of a burnout accident of the field winding. Further, in this case, it is necessary to increase the conductor cross-sectional area of the exciter coil and the armature coil, and accordingly it is necessary to make the stator core and the rotor core large.
It was inevitable that the generator would be large, and the cost of the generator would be high.

If the separately excited synchronous generator is used, the voltage and current required for starting the induction motor can be obtained relatively easily when the induction motor is connected as a load. However, the separately excited synchronous generator is used. If the load impedance straight line changes as shown by the straight line RM2 in FIG. 2 after the induction motor starts, the operating point becomes f and the voltage rises but the current maintains a constant value. . In this case, the actual measurement results of the output voltage E and the output current I (both effective values) of the generator after the load was applied at time t1 were as shown in FIG. 3 (B). As is clear from the figure, when the induction motor is driven using the separately excited synchronous generator, the time required for the output voltage and current of the generator to settle to the rated values (rise time of the rotation speed of the motor) It was unavoidable that the start-up characteristics deteriorated due to the long time.

When a separately excited synchronous generator is used, if the short-time overload output of the generator is to be increased, it is necessary to use a large-sized excitation generator, so the generator becomes large. , The cost is inevitable.

An object of the present invention is to provide a load such as an induction motor, which has a large starting current as compared with the rated current, without particularly increasing the output of the exciter coil and without using a particularly large excitation generator. It is an object of the present invention to provide an engine-driven power generation device that can be driven without any trouble.

[0018]

SUMMARY OF THE INVENTION The present invention has a stator having an exciter coil and an armature coil, and a rotor having a field coil, and the field coil is passed from the exciter coil through an rectifier for exciter output rectification. The present invention relates to an engine-driven power generator that includes a synchronous generator that supplies a field current to the engine and an engine that drives the synchronous generator. In the present invention, an excitation generator that is driven by the engine is further provided. Then, the output current of the exciting generator is superimposed on the field current through the rectifier for exciter output rectification.

Since a crankshaft of an engine is generally equipped with a magnet generator for driving an ignition device and a lamp load, the magnet generator can be used as the excitation generator.

[0020]

With the above construction, the characteristics of the self-excited synchronous generator capable of obtaining a large short-time overload output and the separately-excited synchronous generator capable of easily ensuring the minimum voltage and current necessary for starting the load. Since it is possible to obtain a characteristic having the characteristics of the machine together, it is possible to drive the load satisfactorily without increasing the output of the exciter coil and without using a particularly large-sized exciting generator.

In particular, if a magnet generator mounted on the engine is used as the excitation generator, it is not necessary to prepare a new generator as the excitation generator, so that the cost is not increased. The characteristics can be improved.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention, in which the same parts as those of the conventional generator shown in FIG. 4 are designated by the same reference numerals. In this embodiment, a flywheel magnet generator mounted on the crankshaft of the engine is used as the excitation generator 10 in order to drive the ignition device and the lamp load of the engine. The rotary shaft of the synchronous generator is coupled to the crank shaft of the engine via a power transmission mechanism using a belt or the like.

The magnet generator that constitutes the excitation generator 10 includes a flywheel magnet rotor 10A in which a permanent magnet is attached to the inner circumference of a flywheel to form a magnetic field, an excitation generator coil 10B, and an ignition device. The flywheel magnet rotor 10A is attached to the crankshaft of the engine, and the stator is fixed to a stator attachment portion such as a case of the engine. There is. This magnet generator has
If necessary, a magneto coil for driving a lamp load or the like can be further provided.

The output voltage of the exciting generator coil 10B is input to an exciter output rectifier Rec2 having a diode bridge connection, and the positive and negative output terminals of the rectifier Rec2 are each an exciter output rectifier. R
It is connected to the positive and negative output terminals of ec1.
That is, the output terminal of the exciter output rectifier Rec2 and the output terminal of the exciter output rectifier Rec1 are connected in parallel with their polarities matched. In this embodiment, a field current supply circuit 8 is composed of rectifiers Rec1 and Rec2, a capacitor C1, a transistor TR1 which constitutes a field current control switch, and a flywheel diode D1. The other points are the same as those of the conventional synchronous generator shown in FIG.

In the embodiment of FIG. 1, the excitation generator 10
If the output characteristic is as shown by the curve B in FIG. 2 when no field is provided, and if the exciter coil 1 is not provided and the field current is supplied to the field coil 3 only from the excitation generator 10. Figure 2 shows the output characteristics (when separately excited)
If the output characteristic of the generator 10 for excitation is set so as to be as shown by the curve C, the output characteristic of the generator of FIG. 1 is that the load current is increased from the state in which no load voltage is generated. In such a case, the characteristic changes as k → a → g → j → e → h in FIG. If such characteristics are obtained, when an induction motor whose load impedance at start-up is as shown by a straight line RM1 is used as the load, the operating point at start-up becomes e, and the minimum start-up voltage Em and the minimum start-up current Im By obtaining the above starting voltage and current, the electric motor can be started without any trouble. In addition, the load impedance characteristic after startup is RM
When it changes like 2, the operating point becomes g and the constant voltage characteristic is obtained, so that the starting characteristic can be improved.

Further, since the characteristics of the self-excited synchronous generator can be obtained in a range where the load current is large, the short-time overload output can be increased.

The measured results of the temporal changes of the effective values of the output voltage E and the output current I when the induction motor is loaded on the generator of FIG. 1 are as shown in FIG. After turning on, the characteristic that the output voltage and the current converged to the rated value in a short time was obtained.

In the above-described embodiment, the magnet generator installed in the engine is used as the exciting generator for driving the ignition device of the engine, but the present invention is not limited to this. Instead, a dedicated magnet generator that constitutes an excitation generator may be attached to the rotary shaft of the synchronous generator.

The preferred embodiments of the present invention have been described above. The main aspects of the invention disclosed in the present specification are as follows.

(1) The field coil has a stator having an exciter coil and an armature coil connected in three phases, and a rotor having a field coil, and the field coil is passed from the exciter coil through an exciter output rectifier. In an engine-driven power generator including a synchronous generator to which a field current is supplied, and an engine that drives the synchronous generator,
An exciter generator driven by the engine is provided, the output of the exciter generator is input to an exciter output rectifier rectifier, and the output current of the exciter output rectifier rectifier is an exciter output from the exciter coil. An engine-driven power generator, which is superimposed on a field current supplied through a rectifier for rectification.

(2) A stator iron core, a stator having an exciter coil and a three-phase armature coil wound around the stator iron core, a rotor iron core, and a field wound around the rotor iron core. A rotor having a coil and driven by an engine, a field current supply circuit that supplies a field current to the field coil from the exciter coil through an exciter output rectifier and a field current control switch. And an output voltage control circuit for controlling the field current control switch so as to keep the output voltage of the armature coil at a substantially set value, in an engine-driven power generator, the excitation generator driven by the engine. The field current supply circuit further includes an exciter output rectifier for rectifying the output of the excitation generator, and the output of the exciter output rectifier is the exhaust rectifier. An engine-driven power generator, which is supplied to the field coil as a field current together with the output of the rectifier for sita output rectification.

(3) Stator core, a stator having an exciter coil wound around the stator core and a three-phase armature coil, a rotor core, and a field wound around the rotor core. A rotor having a coil and driven by an engine, a field current supply circuit that supplies a field current to the field coil from the exciter coil through an exciter output rectifier and a field current control switch. And an output voltage control circuit for controlling the field current control switch so as to keep the output voltage of the armature coil at a substantially set value, in an engine-driven power generator, the excitation generator driven by the engine. The field current supply circuit further comprises an exciter output rectifier rectifier for rectifying the output of the excitation generator, and the positive electrode side and the negative electrode of the exciter output rectifier rectifier are provided. Side output terminals are connected to the positive and negative side output terminals of the exciter output rectifier, respectively.

[0033]

As described above, according to the present invention, a field current is supplied from the exciter coil provided on the stator side to the field coil, and the field generator is also driven by the engine. Since the current is supplied, the characteristics of the self-excited synchronous generator that can obtain a large short-time overload output and the separately excited synchronous generator that can easily secure the minimum voltage and current required to start the load It is possible to obtain a generator that also has the characteristics of, and it is possible to satisfactorily drive a load with a large starting current without increasing the output of the exciter coil and without using a particularly large exciter. There is.

In particular, according to the invention described in claim 2, by utilizing the magnet generator attached to the engine for driving the ignition device as the excitation generator,
Since it is not necessary to prepare a new generator as the excitation generator, the characteristics can be improved without increasing the cost.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing output characteristic curves of self-excited and separately-excited synchronous generators together with a load impedance straight line.

3 (A) and 3 (B) show measured results of temporal changes in output voltage and output current of a self-excited synchronous generator and a separately excited synchronous generator used in a conventional engine-driven generator, respectively. FIG. (C) is a diagram showing an actual measurement result of output voltage and output current of the synchronous generator used in the example of the present invention.

FIG. 4 is a circuit diagram showing a configuration of a conventional engine-driven power generator.

[Explanation of symbols]

 1 Exciter coil 2 Armature coil 3 Field coil 5a, 5b Slip ring 6a, 6b Brush 7 Field current control switch 8 Field current supply circuit 9 Output voltage control circuit

Claims (2)

[Claims] 1. A stator having an exciter coil and an armature coil, and a rotor having a field coil,
In an engine-driven synchronous generator including a synchronous generator in which a field current is supplied to the field coil from the exciter coil through an exciter output rectifier, and an engine that drives the synchronous generator, the engine-driven synchronous generator being driven by the engine. An engine-driven power generator, further comprising: an excitation generator, wherein an output current of the excitation generator is superimposed on the field current through a rectifier for exciter output rectification. 2. An engine-driven power generator, wherein a magnet generator for driving an ignition device of the engine is attached to the engine, and the magnet generator also serves as the generator for excitation.