JPS6118400A - Voltage control for generator - Google Patents

Abstract

PURPOSE:To prevent a field coil from burning due to overhead by limiting a field current to continuously flow when the output voltage of a generator largely decreases. CONSTITUTION:The output voltage of an AC generator output from an output coil L3 is full-wave rectified by a rectifier 31 and smoothed by a smoothing circuit 32. A voltage comparator 11 compares a smoothed output voltage Vx with a reference voltage Vs and outputs a control signal V1 for variably controlling the conduction period of a power transistor Q1 for controlling the switching of the field current i1. On the other hand, a voltage comparator 12 compares a rectified output voltage Vi with the smoothed output voltage Vx and outputs a control signal V2 for controlling the continuous conduction period of the transistor Q1. Control signals V1, V2 are supplied through diodes D1, D2 to a drive transistor Q2.

Description

TECHNICAL FIELD The present invention relates to a voltage control device for a generator, and more particularly to a voltage control device for a generator, and in particular to a device that performs negative feedback control to keep the output voltage of the generator constant by switching and controlling the field current of the generator.

Conventional technology FIG. 1 shows an example of the configuration of a conventional generator voltage control device.

The voltage control device for the generator shown in the same figure controls the output voltage of an alternating current generator having a field coil Ll, an excitation coil L2, an output coil L3Y to a constant value, and includes a voltage comparator circuit 1. Wave rectifying and smoothing circuit 2.3° is composed of a power transistor Q1, a driver transistor Q2, and the like.

Here, the field current fl applied to the field coil L1 is
The excitation coil L2ρ is supplied through the full-wave rectifying and smoothing circuit 2. In addition, the comparison input (+) of the voltage comparison circuit 1 is
The generated output voltage taken from the output coil L3) is rectified and smoothed by the full-wave rectification and smoothing circuit 3, and a voltage Vx is given.
Ru. This voltage comparison circuit l performs a comparison operation based on a predetermined reference voltage VB, and outputs the comparison (Vx>Vs)T.
After the sentence phase is inverted via the S driver transistor Q2, the base of the power transistor Q1 can be seen.

The power transistor Q1 is interposed in series in the path of the field current i1 and operates as a switching element.

With the above-described configuration, as shown in FIG. 2(a), the conduction period Ton and the cutoff period Tof of the field current i1 are varied in a complementary manner so that the rectified and smoothed output voltage Vx becomes equal to the reference voltage vIl. controlled.

In addition, negative feedback control is performed so that the generated output voltage becomes a predetermined constant voltage.

However, in this type of generator voltage control device, as shown in Figure 2 (b), when the output voltage (VX) of the generator decreases significantly, the The field current i1 ends up being applied continuously. In this state, the field coil Ll or the power transistor Ql will be overheated by the continuous current, and there is a risk that it will be burnt out or destroyed by heat.

Purpose This invention solves the above problems,
The purpose of this is to limit the continuous flow of field current when the output voltage of the generator drops significantly, and to prevent the field coil from overheating. Burnout can be reliably prevented. r. To provide a voltage control device for a dented generator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the invention will now be described with reference to the drawings.

In each figure, the same reference numerals indicate the same parts corresponding to warts.

FIG. 3 shows an embodiment of a generator voltage control device according to the present invention.

The generator voltage control device shown in the figure includes a field coil Ll,
Excitation coil L2. It controls the output voltage of the alternator by negative feedback to the output coil L3'1e41r, and controls the switching control of the field current 11 through which the field coil L1 is energized. A rectifier circuit 31 that performs full-wave rectification, a smoothing circuit-32 that smoothes the rectified output voltage Vi of this rectifier circuit 31, and a first circuit that compares the smoothed output voltage '/X of this smoothing circuit 32 with a predetermined reference voltage v8. The voltage comparison circuit 11, the rectified output voltage vI, and the smoothed output voltage Vxy! 1- includes a second voltage comparison circuit 12 for mutual comparison. And the above first
The conduction period of the power transistor Ql is variably controlled according to the power generation voltage by the comparison output v1 of the voltage comparison circuit 11, and the second voltage comparison circuit 12
The continuous conduction period of the power transistor Q1 is limited by the comparison output v2 of the power transistor Q1.

Here, a field current 1lrJ is supplied from the exciting coil L27- through the full-wave rectifier circuit 21. The generated output voltage is taken out from the output coil L3. The smoothing circuit 32 is constituted by a large capacity capacitor C2. Reference voltage Vs Ic
, resistors R1, R2, capacitor CI.

A constant voltage circuit 22 consisting of a Zener diode zl is provided. Each comparison output V1. of the second two voltage comparison circuits 11 and 12. After V2 is mutually wired logic (OR logic) by diodes DI and D2,
It is applied to the base of the power transistor Ql via the driver transistor Q2. Together with the driver transistor Q2U and the collector load resistor RO, it forms a common emitter type phase inversion circuit.

Furthermore, a resistor R3 is connected to the rectified output voltage vi.

The voltage is divided by a voltage dividing circuit formed by R4 and input to the smoothing circuit 32. Similarly, the rectified output voltage Vil'J is divided by another voltage dividing circuit including resistors R5 and R61 and applied to the input side of the second voltage comparator circuit.

FIG. 4(a) shows an example of input/output waveforms of the first voltage comparison circuit 11. When the comparison output v1 shown in the figure is "H" (high logic level), the power transistor Q1 is rendered non-conductive.

During the period in which this comparative output (1) is 'H', it changes according to the smoothed output voltage Vx, that is, the generated output voltage. During this 'BIT' period, that is, the pulse width, the generated output voltage is high. When it goes down, it gets longer, and when it goes down, it gets shorter.

Further, FIG. 4(b) shows an example of input/output waveforms of the second voltage comparison circuit 12. The comparison output v2 shown in the figure is “H”.
''(During the period when the logic level is high, the power transistor Q1 is rendered non-conductive.

This period Ts is substantially constant with respect to changes in the generated output voltage, and is determined by the ratio of the resistors R3 and R4 and the ratio of R5 and R6 of the two voltage dividing circuits.

As a result, the comparison output v1 of the first voltage comparison circuit 11 is
The conduction period of the power transistor Q1 is variably controlled in accordance with the power generation voltage, and the continuous conduction period of the power transistor Q1 is limited by the comparison output V21m of the second voltage comparison circuit 12.

FIGS. 5(a) to 5(e) each show an example of the operation of the voltage control device described above.

As shown in Figures (a) to (e), the conduction period Ton (cutoff period Toff) of the field current 11 is short (long) as the smoothed output voltage Vx, that is, the output voltage I ) 9, and the opposite (this makes the smoothed output voltage VX, that is, the generated output voltage, lower J+'i becomes longer (shorter). As a result, the generated output voltage becomes equal to the reference voltage 'VlllC, J
: The predetermined constant voltage ζ is controlled by negative feedback.

What should be noted here is that as shown in Figure (e)J,
This operation is performed when the power generation blade voltage is significantly lowered and the smoothed output '11L voltage Vx is also significantly lowered than the reference voltage Vs,C,0. In this state I, the comparison output v1 of the first 11i pressure comparison circuit 11 becomes "L" continuously. However, the second voltage comparison circuit ↓2
The comparison output V2i of the output voltage V2i periodically takes "H" regardless of the magnitude of the smoothed output voltage VX. And this comparison output v
2, the power transistor QI
Force non-conductivity.

As a result, even when the smoothed output voltage Vx is significantly lower than the reference voltage V8, as shown in FIG. As mentioned above, this period Ts is the length of the resistors R3 and R4.
and the ratio of R5 and R6. Now, without compromising the voltage control function,
It is possible to restrict the field current i1 from continuously flowing through the field coil Ll and the power transistor Ql. In addition, the field coil L1 and the power transistor Q1 can be reliably protected from burnout or thermal damage due to overheating.

In the above embodiment, the control operation was performed based on the voltage taken out from the output coil L3, but in a generator having a voltage detection coil separate from the output coil L3, this detection The control operation may be performed based on the voltage taken out from the coil 70.

Effects As described above, the voltage control device for a generator according to the present invention can restrict the continuous flow of field current when the output voltage of the generator is significantly reduced.
:9 The effect is that it can reliably prevent damage to field coils etc. due to overheating.

In the drawings, the plotter 1 shows an example of the configuration of a conventional voltage control device for a generator, and FIG. 2 shows a waveform chart showing an example of the operation of the device in FIG. 1. A circuit diagram of an embodiment of the voltage control device for a generator according to the present invention is shown. Fig. 4 shows the operating state directly inside the device shown in Fig. 3. Figure 5 shows the internal operation state of the device shown in Fig. 3. It is a T waveform chart which shows an example of a voltage control function.

Ll... Centered field coil R2... Excitation coil of generator R3... Output coil of generator 11...
・First voltage comparison circuit 12... Second voltage comparison circuit 21.31... Full-wave rectifier circuit Ql... Power transistor Q2 as a switching element... Driver transistor Vi... MIN, out ＼
Power voltage 32... Smoothing circuit Vx... Smoothed output voltage Ro '' R5... Resistance CI, C2... Smoothing capacitor Vs... Reference voltage il... Field current T
on: energization period of field current Toff: cutoff period of field current T8: energization suspension period

Claims (1)

[Claims] In a voltage control device for a generator that performs negative feedback control of the generated output voltage by varying the field current applied to the field coil of the generator based on the AC generated output voltage of the generator, the field current a rectifier circuit that performs full-wave rectification of the alternating current generated voltage; a smoothing circuit that smoothes the rectified output voltage of the rectifier circuit; and a second voltage comparison circuit that mutually compares the rectified output voltage and the smoothed output voltage, and the conduction period of the switching element is determined by the comparison output of the first voltage comparison circuit. A voltage control device for a generator, characterized in that the voltage control device performs variable control according to the generated output voltage, and limits the continuous conduction period of the switching element based on the comparison output of the second voltage comparison circuit.