JPH05168207A - Self-exciting type alternating current generator - Google Patents

Abstract

PURPOSE:To obtain the self-exciting AC generator of a capacitor exciting type for enabling voltage at both ends of a capacitor, field winding current, and load voltage, to be prevented from being excessively increased. CONSTITUTION:Into a space between a capacitor exciting winding Wc and a capacitor C arranged on the stator S of the self-exciting AC generator of a capacitor exciting type, a breaker Br is inserted. When the electrifying current Ic of the capacitor exciting winding Wc comes to a set value or more, then the breaker Br is opened, and voltage at both ends of the capacitor C is prevented from being excessively increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor-excited self-excited AC generator.

[0002]

2. Description of the Related Art As shown in FIG. 2, a capacitor-excited self-excited AC generator has an output winding WL on the stator S side.
And a capacitor excitation winding Wc provided so as to have a phase difference of 90 degrees in electrical angle with respect to the output winding WL. These windings WL and Wc are wound on the same iron core, and a breaker Br 'is provided at both ends of the output winding WL.
A load L is connected through. A capacitor C is connected to both ends of the capacitor exciting winding Wc, and the capacitor exciting winding Wc and the capacitor C form a capacitor exciting circuit. A field winding Wf is wound around the iron core K of the rotor R, and a rectifier D is connected to both ends of this field winding.

In the above generator, a voltage is induced in the capacitor exciting winding Wc by the residual magnetism of the field core K at first, and thereby a phase advance current Ic flows from the capacitor exciting winding Wc through the capacitor C. A self-excitation phenomenon occurs due to the magnetizing action due to this phase-advancing current, and at the same time, a field anti-phase electromotive force generated in the field winding Wf by the armature reaction of the capacitor excitation winding causes the field winding Wf to pass through the rectifier D The field current If flows. As a result, the field core K is excited, and the voltages of the output winding WL and the capacitor exciting winding Wc are established.

In this generator, when the breaker Br 'is closed and the load current IL flows from the output winding WL to the load L, the field-reversed phase is generated due to the combined armature reaction of the load current IL and the phase advance current Ic. The electromotive force increases, which increases the field current, so that the output voltage is prevented from decreasing when the load current increases. Therefore, this generator has an advantage that the voltage fluctuation rate is low in addition to the advantage that it is brushless. This type of generator is often used as a portable generator driven by an engine.

FIG. 3 shows an example (measured value) of the relation between the current Ic of the capacitor excitation circuit of the self-excited AC generator, the voltage Vc across the capacitor C, the voltage VL across the output winding, and the load current IL. The power factor cosφ of the load is shown as a parameter. In the figure, the curves, and are the load power factor cosφ of 1.0, 0.8, 0.6 and, respectively.
The case of 0.4 is shown.

As shown in FIG. 3, in the capacitor-excited self-exciting AC generator, the current Ic of the capacitor excitation circuit increases as the load current IL increases. The increasing tendency of the current Ic increases as the load power factor decreases.
In addition, the voltage V across the capacitor C of the capacitor excitation circuit
c increases as the current Ic increases. In order to prevent the capacitor C from being destroyed, it is necessary to suppress the voltage across the capacitor C to be equal to or lower than the withstand voltage of the capacitor.

Conventionally, a breaker BL is inserted between the load L and the output winding WL, and the breaker Br is opened when the output current IL of the generator exceeds the rated current IRL. The voltage higher than the allowable maximum voltage Vcmax is prevented from being applied.

In the above-mentioned self-excited AC generator, it is necessary to set the allowable maximum voltage (withstand voltage) Vcmax of the capacitor C so that the capacitor C is not destroyed when the rated load current IRL flows. The voltage across the capacitor C increases as the power factor decreases even if the load current is the same. Therefore, if the power factor of the load connected to the generator is assumed to be low, use a capacitor C with a high withstand voltage. Must be used. However, since a capacitor with a high withstand voltage is expensive and large, conventionally, assuming that a load with a power factor close to 1.0 is driven, the maximum allowable voltage Vcmax of the capacitor C is shown in FIG.
It was set as shown in.

[0009]

As shown in FIG. 3, the withstand voltage Vc of the capacitor C is set so that the breaker Br is opened when a load current exceeding the rated load current IRL flows as shown in FIG. With this configuration, when the power factor of the load is close to 1.0, it is possible to prevent the voltage across the capacitor C from exceeding the maximum allowable voltage Vcmax. However, if the power factor decreases as shown by the curve in FIG. 3, the voltage Vc across the capacitor C has already exceeded the allowable maximum voltage Vcmax when the rated load current IRL flows, so that the load current exceeding the rated load current is exceeded. Even if the breaker Br is opened when the capacitor C flows, the capacitor C cannot be protected.

Recently, the load of portable generators tends to be diversified, and the power factor thereof is often in a range smaller than 1.0 (range of 0.4 to 0.9). If it is attempted to protect the capacitor C even with a load having a low power factor in the configuration, it is necessary to set the set value of the load current at which the breaker Br operates to a value considerably lower than the rated load current, which is preferable. There wasn't.

In the above generator, since the field current If also increases as the current Ic of the capacitor excitation circuit increases, the temperature of the field winding Wf rises sharply when the load power factor is low. was there. When the temperature of the field winding Wf rises excessively, the impregnating material (varnish) for the field winding Wf
Is softened, the conductive wire forming the field winding Wf may bulge outward due to centrifugal force, and the field winding may eventually come into contact with the iron core of the stator to be broken.

An object of the present invention is to prevent the voltage across the capacitor, the field winding current and the load voltage from becoming excessive when the power factor of the load is bad. To provide a self-excited AC generator.

[0013]

SUMMARY OF THE INVENTION The present invention is directed to a stator having a capacitor excitation winding in which a capacitor is connected in parallel and an output winding to which a load is connected, and a field winding in which a rectifier is connected to both ends. The present invention relates to a self-excited AC generator including a rotor, and in the present invention, a current interruption means is provided to interrupt the energizing current of the capacitor excitation winding when the energizing current exceeds a set value. It was

A circuit protector can be used as the current interruption means. The circuit protector includes a breaker that can be restored and a fuse that needs to be replaced when the circuit protector operates. Any of these may be used in the present invention.

Further, a controllable switch such as a semiconductor switch or a relay is used as the current interrupting means to interrupt the switch when the load current exceeds a set value, and to switch when the load current falls below the set value. May be configured to return to the conductive state.

[0016]

[Function] As described above, the means for cutting off the energizing current of the capacitor exciting winding when the energizing current of the capacitor exciting winding exceeds the set value is provided, so that the energizing current of the capacitor exciting winding exceeds the set value. When the power generation is stopped, it is possible to surely prevent an overvoltage from being applied to the capacitor and an excessive rise in the temperature of the field winding.

[0017]

FIG. 1 shows an embodiment of the present invention. In this embodiment, a breaker Br for interrupting a current when a predetermined current flows between a capacitor exciting winding Wc and a capacitor C is provided. The inserted load L is connected to the output winding WL through a switch SW that is manually opened and closed.
Other points are the same as the conventional generator. Breaker Br
Can be manually restored.

With the configuration shown in FIG. 1, the operating current of the breaker Br is set so that the breaker Br operates when the current Ic flowing through the capacitor excitation circuit exceeds the set current Ica shown in FIG. 3, for example. And the load power factor are
, The operating points of the breaker are points a to d in FIG. 3, respectively. When the breakers are cut off at these operating points a to d, the maximum value of the voltage Vc applied across the capacitor C becomes a value corresponding to the points a'to d'in either case. Also, the voltage applied to the capacitor C can be suppressed to the allowable maximum voltage Vcmax or less.

With the above construction, the maximum value of the load current (the load current at the time when the breaker Br operates) changes according to the power factor of the load, and the load current is limited when the power factor is low. However, when the power factor is high, the original rated current IRL of the generator can flow. Therefore, the capacitor can be protected without lowering the rated current of the generator.

Further, as described above, when the current Ic flowing through the capacitor excitation winding is limited, the field current If is also limited, so that the temperature rise of the field winding Wf can be suppressed. Therefore, it is possible to prevent the varnish impregnated in the field winding Wf from softening and to prevent the winding from swelling due to the centrifugal force, and to eliminate the possibility that a part of the field winding contacts the stator to cause wire breakage. be able to.

When the breaker Br is inserted in the capacitor exciting circuit as described above, the breaker Br 'of the load circuit shown in FIG. 2 can be omitted. Also, since the capacitor exciting current is generally smaller than the load current,
If a breaker is inserted in the capacitor exciting circuit, a small and inexpensive breaker having a smaller current capacity than the conventional one can be used, and the cost can be reduced. The same applies when a fuse or the like is used instead of the breaker.

[0022]

As described above, according to the present invention, there is provided means for cutting off the energizing current of the capacitor exciting winding when the energizing current of the capacitor exciting winding exceeds a set value.
Since the power generation is stopped when the energizing current of the capacitor excitation winding exceeds the set value, without limiting the rated current of the generator and without using a capacitor with a higher withstand voltage than necessary, It is possible to prevent the capacitor from being damaged.

Further, by limiting the current flowing through the capacitor excitation winding, it is possible to prevent the temperature of the field winding from rising excessively, so that the impregnating material of the field winding is softened and the winding is It is possible to prevent bulge and disconnection accident.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram showing a configuration of a conventional generator.

FIG. 3 is a diagram showing an example of the relationship between the capacitor exciting current of the generator, the voltage across the capacitor, and the load voltage and the load current of the generator targeted by the present invention, using the power factor of the load as a parameter.

[Explanation of symbols]

S ... Stator, Wc ... Capacitor excitation winding, WL ... Output winding, R ... Rotor, K ... Rotor core, Wf ... Field winding, D
… Rectifier, Br… Breaker (current interruption means).

Claims (1)

[Claims] 1. A stator having a capacitor excitation winding in which a capacitor is connected in parallel and an output winding to which a load is connected, and a rotor having a field winding in which a rectifier is connected to both ends. In the self-excited AC generator, the self-excited AC generator is provided with a current interruption means for interrupting the energizing current of the capacitor exciting winding when the energizing current exceeds a set value.