JPH0341040B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an alternating current generator, and is particularly intended to prevent damage to an automatic voltage regulator circuit or the like due to an abnormal increase in output voltage during a phase-advanced load.

As a power source for places where commercial frequency power is difficult to obtain, such as civil engineering work sites, a small power supply device called a motor generator is used to generate electricity by driving an easy-to-maintain self-excited alternator (for example, rotating field type) with an internal combustion engine. Widely used. As shown in the circuit diagram shown in Fig. 1, this device detects the so-called residual voltage of the generator G, which occurs when it is driven by an internal combustion engine (not shown), using the excitation winding EC, and outputs it via the rectifier and smoothing circuit _RF1 . By passing a field current through the field winding FC, the output voltage of the armature winding MC is established and power is supplied to the load RL.

By the way, in order to stabilize the output voltage in such a power supply device, for example, an automatic voltage regulator as described below is usually provided. This circuit detects the output voltage of armature winding MC
(Other detection methods can be used.) The output of
Error voltage detection circuit EV through rectifier smoothing circuit RF ₂
In addition, the difference from the reference output voltage set here is detected, and the main transistor Q ₂ is turned on and off in response to changes in the output voltage via the Darlington-connected control transistor Q ₁ . This is to control the field current and stabilize the output voltage in response to fluctuations in the load, etc. For example, when the detected output voltage becomes larger than the set reference output voltage, the difference output causes transistor Q ₁
turns on, and the base current of main transistor _Q2 is bypassed by the collector-emitter circuit of _Q1 , turning it off and cutting off the field current. Also, when the detected output voltage becomes smaller than the set reference output voltage, transistor Q ₁ is turned off and main transistor Q ₂ is turned on to increase the output voltage, so that the output voltage of armature winding MC is always set as the set reference output. It operates to match the voltage. In the figure, LC is the auxiliary winding for driving the transistor, RF ₃ is its rectifier and smoothing circuit, REC ₁ , REC ₂ , and REC ₃ are the rectifier circuits, C ₁ , C ₂ , and C ₃ are the smoothing capacitors, and D is the flywheel diode. It is connected in parallel to the field winding FC, and protects the circuit from high reverse voltage by absorbing the reverse voltage generated in the field winding FC when the main transistor _Q2 is off.

However, as mentioned above, in a power supply device equipped with an alternating current generator that has a flywheel diode D in the field winding FC, a capacitive load with a power factor correction capacitor, such as a high power factor mercury lamp, is used as a load. When connected, the armature reaction due to the advanced phase current flowing through the armature winding MC may cause a magnetizing effect, leading to an increase in the output voltage. In other words, as is well known, the armature reaction generates a positive-phase magnetic field and a negative-phase magnetic field, and the positive-phase component performs a magnetizing action that strengthens the field of the generator G, while the negative-phase component moves in the opposite direction to the rotor. The rotating magnetic field interlinks with the field winding FC at twice the synchronous speed of , and this rotating magnetic field induces an alternating current voltage of twice the frequency in the field winding FC.

Here, an automatic voltage regulator operates in response to the increase in output voltage due to the magnetizing effect as described above.
The above action turns off the main transistor _Q2 , interrupts the circuit of the field winding FC, and works to suppress the rise in voltage. However, as mentioned above, there is a flywheel diode D in parallel to the field winding FC.
is provided, so the frequency twice the above (50
A pulsating direct current is circulated through the field winding FC using a voltage of 100 Hz (in the case of Hz), causing a self-excitation effect. Therefore, the output voltage of the armature winding MC may increase even though the main transistor _Q2 is off.

An object of the present invention is to provide an automatic voltage regulator that can effectively suppress the self-excitation effect that occurs when the field circuit is turned off as described above with a simple circuit, and improve the stabilization performance of the output voltage. Next, the details will be explained using the drawings.

FIGS. 2 and 3 are circuit diagrams of essential parts for explaining the principle of the present invention and circuit diagrams for explaining its operation, and the features of the present invention are as follows.
That is, at the same time, an off detection circuit OD is provided to detect when the circuit of the field winding FC is turned off and when the polarity of the double frequency induced voltage has become a polarity that does not cause the rectification action of the flywheel diode D (Fig. The switching circuit S is provided, which forms a bypass circuit for the flywheel diode D based on its detection output.

When the double frequency induced voltage has a polarity that causes the flywheel diode D to rectify,
When a half-wave current I _a1 is applied to the field winding FC as shown in Fig. 3, and the polarity of the induced voltage is such that the flywheel diode D does not produce a rectifying action, the switching circuit S causes the above I a1 to flow as shown in Fig. 3. A half-wave current I _a2 of opposite polarity to _a1 is passed through the field winding FC, resulting in an alternating current flowing through the field winding FC. In this way, the average value of the alternating current is zero, and the resulting magnetomotive force is also zero, so that the self-excitation effect when the main transistor _Q2 is off is prevented. As a result, the main transistor Q ₂ will not continue to lose its voltage stabilizing function due to the increase in the output voltage when the main transistor Q ₂ is off, and an abnormal increase in the output voltage can be prevented. Next, the present invention will be explained using a specific example circuit.

FIG. 4 is a circuit diagram showing a specific example of the present invention (the same reference numerals as in FIG. 1 indicate equivalent parts). That is, the first point is that a bias diode _D1 is connected in series between the field winding FC and the main transistor _Q2 so as to be in the forward direction with respect to the field current. In the second, the collector-emitter is connected to both ends of the field winding FC, and the base is connected to the connection point of the diode D ₁ and the main transistor Q ₂ and the connection point of the diode D ₁ and the opposite side through the resistor R ₁ . The short circuit transistor _Q3 is connected to the FC end of the field winding.

In this way, when the main transistor _Q2 is on and a current flows in the direction of the solid arrow in the figure through the field winding FC, the shorting transistor _Q3 becomes reverse biased and maintains the off state.

On the other hand, when the output voltage becomes even slightly higher than the set reference voltage due to the magnetizing effect and the main transistor _Q2 is turned off, the polarity of the double frequency voltage induced in the field winding FC is shown by the solid line in the figure. When the polarity is such that the current flows in the direction of the arrow, the shorting transistor
Q ₃ is reverse biased and turned off. Also, when the induced voltage has a polarity that causes current to flow in the direction of the dotted arrow in the figure, the short-circuit transistor Q ₃ is connected to the resistor R ₁
The forward bias is once turned on via . That is, from the above, when the main transistor Q ₂ is on,
Since the shorting transistor _Q3 is always turned off,
No short-circuiting operation of the field winding FC is performed. However, only when the main transistor Q ₂ is turned off, that is, the supply of field current is stopped, and the polarity of the double frequency induced voltage becomes such that a current flows in the opposite direction to the direction of flow of the field current. , short circuit transistor Q ₃
turns on and creates a bypass circuit for flywheel diode D.

That is, when the polarity of the double frequency induced voltage is such that a current flows in the direction of the solid arrow in the figure, the rectifying action of the flywheel diode D causes an AC half-wave current to flow through the field winding FC. Furthermore _, in the next half wave, when the polarity of the induced voltage is such that a current flows as shown by the dotted line in the figure, causing rectification by the flywheel diode D, the field winding is A half-wave current opposite to the above is passed through the FC. As a result, an alternating current with an average value of zero is passed through the field winding FC, and the magnetomotive force also becomes zero, causing the main transistor to
The self-excitation effect when Q ₂ is off is prevented.

In addition, in the above, the auxiliary winding is connected to the alternator G.
Although the LC is provided to obtain driving power for the transistors Q ₁ , Q ₂ and the like, the output of the excitation winding EC and other windings may be used, for example.

As is clear from the above description, according to the present invention, an internal combustion engine-driven power supply device using a self-excited alternator with good output control characteristics can prevent an increase in output voltage due to magnetization effect during a capacitive load. can be obtained, and its practical effects are remarkable.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a conventional device, Figures 2 and 3 are
The drawings are a main part circuit diagram for explaining the principle of the present invention and a circuit diagram for explaining the operation, and FIG. 4 is a circuit diagram showing a specific example of the present invention. G...Self-excited alternator, MC...Armature winding, SC...Output voltage detection winding, EC...Excitation winding, FC...Field winding, LC...Auxiliary winding for transistor drive , RF ₁ , RF ₂ , RF ₃ ... rectifier smoothing circuit,
REC ₁ , REC ₂ , REC ₃ ... Rectifier circuit, C ₁ , C ₂ , C ₃
... Smoothing capacitor, D ... Flywheel diode for reverse voltage absorption, Q ₁ ... Control transistor, Q ₂ ... Main transistor, EV ... Error voltage detection circuit, OD ... OFF detection of field winding circuit circuit,
S... Switching circuit for short circuit, Q ₃ ... Transistor for short circuit, R ₁ ... Resistor.

Claims (1)

[Claims] 1. A main transistor Q _{2 is connected in series with a field winding FC equipped with a flywheel diode D in the opposite direction to the field current, and this main transistor Q 2 is} connected to an armature winding. In an alternator in which the output voltage is stabilized by on/off control based on the output of an error voltage detection circuit EV that compares the detected output voltage of the line MC with a reference output voltage, an AC generator is connected in series with the field winding FC. , a bias diode _D1 having an anode connected to one end side of the field winding FC and a cathode connected to the collector side of the main transistor _Q2 is provided, and in parallel with the flywheel diode D, the collector is connected to the flywheel diode D1. Connected to the cathode side of wheel diode D,
A short-circuiting transistor Q3 has an emitter connected to the anode side of the flywheel diode D, and a base connected to the cathode side of the flywheel diode D and the bias diode _D1 via a _{resistor R1} . AC generator provided.