JPH11285144A - Self-excited generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a self-excited generator, in which the overheat of a field winding which is caused by the increase in a field current, is avoided by the operation of an automatic voltage regulator, when the rotating speed has declined due to an overload. SOLUTION: A self-excited generator has a stator which has an excitation winding 1 and an output winding 2, a rotor 5 which has a filed winding 4 to which a field current is supplied from the excitation winding 1 through a feeding mechanism composed of slip rings 6a and 6b and brushes 7a and 7b pressed against the slip rings 6a and 6b and an automatic voltage regulator 8, which controls the field current supplied to the field winding 4 from the excitation winding 1, so as to keep the output voltage of the output winding 2 constant. A current cut-off means 9, which cuts off the field current when the field current exceeds a predetermined value, is inserted into the current route of a field current If.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-excited generator having an automatic voltage regulator driven by a prime mover of an internal combustion engine to supply power to a load.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional self-excited generator of this type. In FIG. 1, reference numeral 1 denotes an excitation winding provided on a stator of a generator, and 2 denotes an output winding also provided on the stator.
Supplied to Reference numeral 4 denotes a field winding wound around a salient pole type field iron core of a rotor 5 of the generator. Both ends of the field winding are connected to slip rings 6a and 6b provided on the rotor, respectively. I have. Brushes 7a, 7b held on the stator side of the generator are brought into contact with the slip rings 6a, 6b, respectively, and the brushes 7a, 7b and the slip rings 6a, 6b,
6b constitute a power supply mechanism, and a field current If is supplied from the excitation winding 1 to the field winding 4 through the automatic voltage regulator 8 and the power supply mechanism.

The automatic voltage regulator 8 detects the output voltage Vt of the output winding 2 and controls the field current If supplied from the exciting winding 1 to the field winding 4 to thereby control the output winding Vt. Is automatically adjusted to the set value.

A self-excited generator of this type used in a portable power generator is used in an overload state, the output current of which exceeds the rated current continues for a long time, and the output winding of the generator is burned. In order to prevent this, a current interrupting means 10 is inserted in the output current supply circuit. The current cutoff means cuts off a circuit for supplying the output current when an output current equal to or more than a set value continuously flows from the output winding 2 to prevent heating of the output winding.

[0005]

As described above, in the conventional self-excited generator, the current interrupting means 10 is inserted in the output current supply circuit. By causing the current interrupting means 10 to perform an interrupting operation to interrupt the output current, overheating of the output winding 2 of the generator can be prevented.

[0006] However, the conventional self-excited generator provided with the automatic voltage regulator has a problem that it is impossible to prevent the field winding from overheating when the rotation speed is reduced.

That is, when an overload condition occurs in the self-excited generator and the rotation speed of the prime mover falls below the rated rotation speed and the output voltage of the generator falls, the automatic voltage regulator 8
Performs an operation of increasing the field current If to compensate for a decrease in the output voltage due to a decrease in the rotation speed. Therefore, the field current If flowing through the field winding 4 is such that the generator is rotating at the rated rotation speed. It increases more than time. Therefore, when the generator is overloaded and its rotational speed is reduced, even if the output current is not excessive (the current is lower than the set value at which the current interrupting unit 10 performs the interrupting operation), the field winding is stopped. Excessive field current will flow through the line 4 and the temperature of the field winding will increase. Further, when the rotation speed of the generator decreases, the amount of cooling air for cooling the rotor of the generator decreases, so that the cooling effect of the field winding decreases.

As described above, when the generator is overloaded and its rotation speed is reduced, the heat generated by the field winding is increased and the cooling is also deteriorated, so that the temperature of the field winding decreases. There was a risk that the temperature of the field winding would rise excessively and burn out. When the temperature of the field winding rises, the impregnating material of the field winding softens and the field winding expands radially outward, so that the field winding comes into contact with the inner periphery of the stator. There was danger.

An object of the present invention is to prevent the output current from exceeding an allowable value, and when the rotation speed is reduced, an excessive field current flows through the field winding to overheat the field winding. It is an object of the present invention to provide a self-excited generator capable of preventing the occurrence of the above.

[0010]

SUMMARY OF THE INVENTION The present invention comprises a stator having an excitation winding and an output winding, and a field current from the excitation winding through a feed mechanism having a slip ring and a brush contacting the slip ring. A rotor having a field winding to which is supplied, and an automatic voltage regulator for controlling a field current supplied from the excitation winding to the field winding so as to keep the output voltage of the output winding at a set value. The present invention relates to a self-excited generator provided with:

In the present invention, current interrupting means for interrupting the field current when the field current becomes equal to or higher than the set value is inserted in the circuit for supplying the field current.

The above set value is, for example, larger than the value of the field current when the generator is operated at the rated rotation speed and the rated output current, and when the generator is rotating at the rated rotation speed. A value of the field current corresponding to an allowable maximum value of the output current of the output winding and a value equal to or less than the allowable maximum value of the field current that needs to be set to prevent overheating of the field winding. Is set to

With the above configuration, when the generator is rotating at the rated rotation speed, the field current is cut off before the output current value exceeds the allowable maximum value, and the output current decreases. Overheating of the winding can be prevented.

When the generator is overloaded, the rotation speed is reduced and the output voltage is reduced, and the automatic voltage regulator operates to increase the field current. When the field current exceeds a set value, the current is reduced. Since the interrupting means performs an interrupting operation to interrupt the field current, overheating of the field winding can be prevented.

[0015]

FIG. 1 shows an example of the configuration of a self-excited generator according to the present invention. In FIG. 1, reference numeral 1 denotes an excitation winding wound around a stator core (not shown) of the generator. An output winding 2 is also wound around the stator core, and the output of the output winding is supplied to a load 3.

Reference numeral 4 denotes a field winding provided on a rotor 5 of the generator. The field winding is a salient pole type field iron core (not shown) fixed at both ends to a rotating shaft supported by bearings. It is wound around the pole via an insulating bobbin. The start and end of winding of the field winding are determined by slip rings 6a and 6b provided on the rotor 5.
Connected to each other. Slip rings 6a, 6b
A pair of brushes 7a held on the stator side of the generator,
7b are brought into contact with each other,
a, 6b and brushes 7a, 7b constitute a power supply mechanism, and a field current If is supplied from the excitation winding 1 to the field winding 4 through the automatic voltage regulator 8 and the power supply mechanism. .

The automatic voltage regulator 8 is connected to the output winding 2 of the generator.
The field current If supplied from the exciting winding 1 to the field winding 4 is controlled so as to keep the output voltage Vt at the set value.

In the present invention, the current interrupting means 9 is inserted in the circuit for supplying the field current If. The current cutoff means 9 cuts off the field current If when the magnitude of the field current If becomes equal to or larger than a set value.

When the rotor 5 of the generator is driven by a prime mover such as an internal combustion engine to start rotation, initial excitation is performed by the residual magnetic flux of the field core, and a voltage is induced in the exciting winding 1. When the excitation current is supplied to the field winding 4 by this voltage, the voltage generated in the excitation winding 1 and the output winding 2 rapidly rises, and the output voltage is established in the output winding 2, and the generator operates by itself. Operates as an excitation generator. If a small permanent magnet is attached to the magnetic pole portion of the field core and the initial excitation is performed by the field of the permanent magnet, the initial excitation can be performed more reliably.

The automatic voltage regulator 8 comprises a known circuit. In the illustrated example, the automatic voltage regulator 8 is connected between a circuit in which two rectifiers and two thyristors are connected in a single-phase bridge, and a DC output terminal of the bridge circuit. A flywheel diode connected with the cathode directed to the positive terminal side of the DC output terminal to rectify the AC output of the exciting winding 1 to produce a field winding 4
Bridge rectifier circuit 81 that supplies exciting current If
An output voltage detection circuit 82 for detecting the output voltage Vt of the output winding 2 of the generator, and a mixed bridge rectifier circuit 81 when the output voltage Vt detected by the output voltage detection circuit 82 is equal to or less than a set value. A thyristor control for providing a trigger signal to the thyristor to make the thyristor conductive, and controlling the conduction and cutoff of the two thyristors so that the trigger signal is not applied to the two thyristors when the output voltage Vt exceeds a set value. And a circuit 83.

As the current interrupting means 9, a resettable DC breaker, a fuse or the like can be used. When the load 3 of the generator is a motor or the like and a large starting current flows for a short time at the time of starting the load, the current interrupting means 9 is a large field that flows for a short time corresponding to the starting current. One having a reverse time limit characteristic that is not interrupted by a magnetic current is used.

The set value of the field current (cutoff current value) for causing the current cutoff means 9 to perform the cutoff operation is larger than the value of the field current when the generator is operated at the rated rotation speed and the rated output current. , And the field current corresponding to the maximum allowable output current when the generator is rotating at the rated speed (the maximum allowable output current that must be set to prevent overheating of the output winding) The value of If is set to be equal to or less than the maximum allowable value of the field current If which needs to be set in order to prevent overheating of the field winding 4.

FIG. 2 shows the output characteristics of the self-excited generator provided with the automatic voltage regulator 8. In FIG.
A curve a shown by a solid line shows a relationship between the output current IL and the output voltage Vt when the generator is rotating at the rated rotation speed N0, and a curve b shown by a solid line shows the output current IL in that case.
And the field current If [If (N0)]. The curves c and d shown by broken lines show the output current IL and the field current If when the rotation speed of the generator is lower than the rated rotation speed N0 and N2 (N0>N1> N2). [If the rotation speed is N1, If (N1), N
2 shows the relationship with If (N2)].

As shown in FIG. 2, the set value of the field current (cut-off current set value) Ifs for causing the current means 9 to perform the cut-off operation is, as shown in FIG. The maximum allowable field current that must be set to prevent overheating of the field winding 4 and that is larger than If0 of the field current when operating at The value is set to a value equal to or smaller than the field current corresponding to the maximum allowable value of the output current ILS which needs to be set in order to prevent the output winding from overheating when operating at the speed N0.

Therefore, when the output current IL becomes IL0 below the rated output current ILS while the generator is rotating at the rated rotation speed N0, the field current If [If (N0)] reaches the cutoff current set value Ifs. The field current is cut off. As a result, it is possible to prevent the output winding 2 from overheating when the output current exceeds the allowable maximum value ILS.

When the rotation speed of the generator is reduced to N1 and N2 lower than the rated rotation speed N0, the field currents If (N1) and If (N2) are reduced to the rated rotation speed N0 even if the output current is within the rated range. Is larger than the field current If (N0) at the time of. In the conventional generator not provided with the current interrupting means 9 for interrupting the field current, the field windings If1 and If2 may exceed the allowable maximum value at this time, and the field winding may be overheated. Then, the current interruption means 9 is provided in the circuit for supplying the field current.
Is inserted, and when the field current exceeds the cutoff current set value Ifs, the field current is cut off, so that the field winding 4 can be prevented from overheating.

The current interrupting means 9 used in the above example is the same as that shown in FIG.
In the conventional example shown in FIG. 1, the current interrupting means 10 may be smaller than the current interrupting means 10 provided for interrupting the output current of the generator, so that it is less expensive than the current interrupting means 10 conventionally used. Can be configured.

[0028]

As described above, according to the present invention, in a self-excited generator provided with an automatic voltage regulator, current interrupting means for interrupting a field current when the field current exceeds a set value. Is inserted in the field current supply circuit, which not only prevents the output current of the generator from exceeding the allowable maximum value and overheating of the output winding, but also reduces the rotation speed of the generator and automatically Even when the field current exceeds the set value due to the function of the voltage regulator, the field current can be cut off to prevent the field winding from overheating.

Further, according to the present invention, as the current interrupting means, an inexpensive one having a smaller interrupting current capacity than that conventionally used can be used, so that the manufacturing cost of the self-excited generator can be reduced. Can be.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration example of a self-excited generator according to the present invention.

FIG. 2 is a diagram showing output characteristics of the self-excited generator of FIG. 1;

FIG. 3 is a circuit diagram showing a configuration example of a conventional self-excited generator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Excitation winding 2 Output winding 3 Load 4 Field winding 5 Rotor 6a, 6b Slip ring 7a, 7b Brush 8 Automatic voltage regulator 9 Current cutoff means

Claims (2)

[Claims] 1. A field winding to which a field current is supplied from the excitation winding through a power supply mechanism having a stator having an excitation winding and an output winding, and a slip ring and a brush contacting the slip ring. A self-contained rotor comprising: a rotor having a wire; and an automatic voltage regulator for controlling a field current supplied from the excitation winding to the field winding so as to maintain an output voltage of the output winding at a set value. A self-excited generator, wherein current interrupting means for interrupting the field current when the field current becomes equal to or more than a set value is inserted in a circuit for supplying the field current. 2. The state in which the set value is larger than the value of the field current when the generator is operated at a rated rotation speed and a rated output current, and the generator is rotating at the rated rotation speed. The value of the field current corresponding to the allowable maximum value of the output current of the output winding and the allowable maximum value of the field current that need to be set to prevent overheating of the field winding The self-excited generator according to claim 1, wherein the generator is set to a value.