JPS6329506B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC machine having an accessory device for preventing transient deterioration of commutation during sudden changes in load.

One of the most important functions that affects the performance of a DC machine is rectification. This rectifying action occurs within a very short time when the armature coil is short-circuited by the brush.
This is a phenomenon in which the direction of the current flowing through the armature coil is reversed. However, since the coil has inductance, it generates a back electromotive force or reactance voltage according to the rate of change of current during current reversal, and attempts to prevent this change. Therefore, a commutating pole is provided to cancel this reactance voltage and to perform smooth rectification. This commutating pole generates a speed electromotive force in the rectifying coil by cutting off the magnetic flux coming out from under the commutating pole, and this electromotive force cancels out the reactance voltage. This electromotive force is called rectified electromotive force, but since the commutating pole is excited by the armature current, the commutating magnetic flux also increases in proportion to the armature current, and the commutating electromotive force generated by cutting the commutating magnetic flux also applies to the armature. Occurs in proportion to current. On the other hand, reactance voltage is generated in proportion to armature current, so
The rectified electromotive force can always completely cancel out the reactance voltage as the armature current increases or decreases. Therefore, good commutation can be maintained over a wide range of armature currents, ie, over a wide range of loads.

However, when the armature current suddenly changes, an eddy current is generated in the magnetic path of the commutator flux, and this eddy current prevents the change of the commutator flux, so there is a transient state in which the commutator flux is not proportional to the armature current. arise. At this time,
The rectified electromotive force is also not proportional to the armature current, and there is an excess or deficiency between it and the reactance voltage.
This excess/deficiency voltage is applied between the brush and the commutator and generates sparks. This is transient deterioration of rectification.

Conventionally, in order to prevent this transient deterioration of rectification, an inductive shunt is provided. The principle of improving transient rectification using this induction shunt will be explained with reference to FIG.

The inductive shunt 1 is composed of a reactor 2 and a resistor 3 connected in series, and a compensation coil 5 and a commutator coil 6 (terminals) connected in series to an armature coil 4.
GH) are connected in parallel. In such a configuration, if the armature current I is constant,
A constant shunt current i 1 that is determined by the ratio of the combined resistance R _C of the compensation coil 5 and the commutator coil 6 to the resistance R _X of the inductive shunt ₁ flows through the inductive shunt 1 . This shunt current i ₁
is usually about 1 to 2% of the armature current I.
As a result of part of the armature current I being shunted to the induction shunt 1, the current i2 flowing through the compensation coil 5 and the commutating coil ₆ becomes smaller than the armature current I, but the rectified electromotive force maintains a predetermined value. In order to lower the magnetic resistance of the interpole,
A predetermined interpolation magnetic flux is generated.

Now, the operation when the armature current I suddenly changes will be explained as follows when the current increases.
The shunt ratio when the current suddenly changes is determined by the ratio of the inductance L _C of the compensation coil 5 and the commutator coil 6 to the inductance L _X of the induction shunt 1. L _X /L _C to R _X /
If it is set larger than R _C , when the current suddenly changes, the current will flow more easily to the inductive shunt 1 than when the current is constant, and accordingly, an additional current will flow to the compensation coil 5 and the commutator coil 6. Thinking to the extreme, if no current flows through induction shunt 1 when the current suddenly changes, then
Current determined by R _C / _R
The current i 2 flowing through the compensation coil 5 and the commutator coil ₆ increases by the amount of current flowing through the compensation coil 5 and the commutator coil 6. This increase in current i ₂ results in an increase in the magnetomotive force that excites the interpolation magnetic flux.
This increase has the opposite polarity to the magnetomotive force of the eddy current, which has a demagnetizing effect, so it cancels the magnetomotive force of the eddy current,
Temporary decrease in magnetic flux due to eddy current can be prevented.

This is the principle of induction shunt 1 _, but the larger the shunt ratio when the _{current is constant} , that is, the smaller the ratio _{of R} The larger it is, the more effective it is. Therefore, since the increase in the current i ₂ flowing through the compensation coil 5 and the commutating coil 6 when the current suddenly changes becomes large, a larger magnetomotive force for eddy current compensation can be obtained. In this case, increasing the diversion ratio to reduce R _X /R _C means reducing R _X when considering one machine as the target. Furthermore, setting L _X /L _C to be larger than R _X /R _C means increasing the value of L _X when L _C , R _C and R _X are determined.

When L _X is increased and R _X is decreased, the time constant L _X /R _X becomes larger as a result. If this time constant L _X / _R

FIG. 2 shows an example when the current increases, and FIG. 2a shows the rise of the armature current I and the rise of the shunt current _i1 . Furthermore, the magnitude when the shunt current i ₁ rises and reaches a constant value is shown in accordance with the magnitude after the rise of the armature current I.

Even if the armature current I rises to a certain value, the shunt current _i1 has a large inductance, so its rise is delayed. Then the armature current I
Even if it maintains a constant value, it will take some time for the delay in the rise to recover. That time is
It depends on L _x /R _x , and it takes approximately T=4L _x /R _x time. During that time, there is a shortage of current in the induction shunt 1, and an extra current flows through the compensation coil 5 and the commutator coil 6, increasing the magnetomotive force.

On the other hand, if the magnetomotive force of the eddy current disappears quickly as shown in FIG. However, the balance is lost and the commutating magnetic flux becomes larger than necessary, and as a result, the rectified electromotive force becomes larger than the reactance voltage, resulting in deterioration of rectification, as shown in FIG. 2c.

In addition, in a DC machine that uses the induction shunt 1, it is necessary to design the magnetic resistance of the magnetic circuit to be smaller than when the induction shunt is not installed, so that a predetermined interpolation magnetic flux is produced after subtracting the shunt current in advance. However, due to design, there is a limit to how much magnetic resistance can be reduced. That is, there is a limit to the magnitude of the shunt current that can be obtained.

This invention was made based on the above circumstances, and it improves rectification when the armature current suddenly changes, prevents the occurrence of adverse effects when the current is constant, and prevents sudden changes, that is, the generation of large eddy currents. The purpose of the present invention is to obtain a DC machine that can improve rectification even in the case of a DC motor.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a diagram showing the configuration of this embodiment, and the same parts as in FIG. 1 are designated by the same reference numerals, and the explanation thereof will be omitted. In this embodiment, as shown in FIG. 3, an auxiliary commutator coil 7 is provided in which the armature current I flowing through the commutator coil 6 is induced by mutual induction (mutual induction coefficient: M). In addition, di/dt is added to the armature circuit.
A detector 8 is provided to constantly detect di/dt of armature current I. Furthermore, the detection signal S of the di/dt detector 8 is input, and the voltage V induced in the auxiliary commutator coil 7 is
Generate a voltage V ₁ that cancels (Mdi/dt),
In addition to preventing short circuit current due to voltage V, di/dt
Generates an additional voltage V ₂ according to the degree of eddy current generation in the commutating magnetic path of the DC machine according to the signal S,
An auxiliary commutating coil excitation device 9 is provided to flow an auxiliary commutating coil current I ₀ for canceling the eddy current magnetomotive force.

In the above configuration, when the armature current I suddenly changes, due to mutual induction between the commutator coil 6 and the auxiliary commutator coil 7, a voltage V (Mdi/dt) proportional to the armature current change di/dt is generated. is induced in the auxiliary commutator coil 7. In addition, the armature circuit
Since the di/dt detector 8 constantly detects the di/dt of the armature current I, when a sudden change in the armature current I is detected, the auxiliary commutating coil exciter 9 is activated by the detection signal S. A voltage V ₁ that cancels out the voltage V induced in the auxiliary commutator coil 7 is generated to prevent short-circuit current caused by the voltage V. Furthermore, the auxiliary commutator coil exciter 9 generates an additional voltage V ₂ according to the degree of eddy current generation in the auxiliary magnetic path of the DC machine according to the di/dt signal S, thereby increasing the eddy current magnetomotive force. Flow an auxiliary commutator coil current I ₀ for cancellation.

As described above, according to this embodiment, the auxiliary commutator coil 7 is provided in which the armature current I flowing through the commutator coil 6 is induced by mutual induction, and when the armature current I suddenly changes, the commutator coil 7 The voltage generated in the auxiliary commutator coil 7 is canceled by the electromagnetic mutual induction between the auxiliary commutator coil 7 and the auxiliary commutator coil 7, and the decrease in the commutator magnetic flux caused by the eddy current generated in the commutator magnetic path is further reduced. Since an auxiliary commutator coil excitation device 9 is provided to apply a voltage for causing an excitation current to flow through the auxiliary commutator coil 7 in order to compensate, the armature current I is increased as shown in FIGS. By flowing the auxiliary commutator coil current I ₀ that matches the degree of eddy current generation, both in the case of a sudden change and in the subsequent case when the current is constant, the transition between the transient rectified electromotive force and the reactance voltage can be reduced. It is possible to compensate for unbalance and prevent transient deterioration of rectification. Therefore, it is possible to match the time constant of the auxiliary pole circuit with the time constant of the generation and extinction of eddy currents, and by setting the magnitude of the additional voltage _V2 , it is possible to set the conventional inductive shunt. It can also be used when there is a sudden change, that is, when an eddy current occurs.

Note that this invention is not limited to the above embodiments. For example, the time constant of the auxiliary interpolation circuit may be adjusted using a series reactor or a low resistor, if necessary. Further, in order to match the waveforms of the magnetomotive force due to the auxiliary pole current and the magnetomotive force of the eddy current, forcing may be performed or a reverse voltage may be applied in the same manner as in the case of controlling the main pole field current. It goes without saying that various other modifications can be made without departing from the gist of the invention.

As explained above, according to the present invention, it is possible to prevent commutation deterioration when the armature current suddenly changes, that is, when the load suddenly changes, prevent the occurrence of adverse effects when the current is constant, and allow higher armature current changes. A DC machine with high control responsiveness and excellent rectification performance can be obtained.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a DC machine equipped with an induction shunt, Figures 2 a to c are waveform diagrams for explaining the operation of Figure 1, and Figure 3 is a diagram of a DC machine in an embodiment of the present invention. The configuration diagrams and FIGS. 4a to 4c are waveform diagrams for explaining the operation of FIG. 3. 4... Armature coil, 5... Compensation coil, 6... Compensation coil, 7... Auxiliary commutator coil, 8... di/dt detector, 9... Auxiliary commutator coil excitation device.

Claims (1)

[Claims] 1. In a DC machine equipped with a commutating pole coil, an auxiliary commutating coil in which the armature current flowing in the commutating coil is induced by mutual induction, and an excitation device that generates a voltage for canceling the voltage caused by the auxiliary commutator coil and at the same time generates a voltage for causing an excitation current to flow through the auxiliary commutator coil so as to compensate for a decrease in the commutator magnetic flux caused by the eddy current in the auxiliary magnetic path; A DC machine characterized by comprising: