JPS6255378B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a protection device for a separately excited DC motor,
The present invention relates to a protection device for separately excited DC motors, which is particularly suitable for those using DC power supplies with large fluctuations in output voltage.

The speed of a separately excited DC motor can be freely controlled without the need for complicated and large area-occupying auxiliary equipment. For this reason, recently, it has been considered to use separately excited DC motors as motors for vehicles. However, the power supply voltage of the overhead wire supplied to the vehicle fluctuates widely, and in particular, a device for protecting the excited DC motor is required in response to increases in the power supply voltage. Such protection devices include a device that detects overcurrent in the armature circuit and shuts off the armature circuit based on the detection, or a device that compares the voltage of the armature circuit with a reference command value and adjusts the output voltage of the semiconductor rectifier. A device to suppress this could be considered. This latter protection device will be described below.

FIG. 1 is a circuit diagram of a conventional protection device. In the figure, 1 is a semiconductor rectifier for the armature circuit which rectifies the AC from the power supply into DC and supplies it to the armature circuit, 2 is the same semiconductor rectifier for the field circuit, and 3 is the electric motor of the separately excited DC motor. child, 4 is its commutator winding,
5 is a separately excited field winding, and 6 is a reactor. 7
is a detection resistor inserted in the armature circuit, 8 is a voltage detector that detects the voltage across the detection resistor 7, 9 is a reference command value generator that generates a certain reference voltage, and 10 is the reference voltage mentioned above. This is a subtracter that subtracts the voltage detected by the voltage detector 8 from .

The operation of this conventional protection device is shown in Figures 2 and 3.
This will be explained with reference to the voltage and current waveform diagrams shown in the figure. FIG. 2 is a waveform diagram of the output voltages of the semiconductor rectifiers 1 and 2, and FIG. 3 is a waveform diagram of the current in the armature circuit. Now, at time t ₁ , semiconductor rectifiers 1 and 2
Suppose that the output voltage of increases from voltage V ₁ to voltage V ₂ . In this case, the armature current increases, and if this becomes an overcurrent, a flashover occurs, which causes other installed protection devices to operate and stop the motor. Further, even if flashover does not occur, sparks are generated violently, resulting in severe wear of the brush. By the way, in the conventional device shown in FIG. 1, the output voltage of the voltage detector 8 increases in accordance with an increase in current, and when this exceeds the reference voltage, a corresponding signal is sent to the semiconductor rectifier 1. is applied to the gate of Therefore, the output voltage of the semiconductor rectifier 1 is suppressed from increasing, thereby preventing flashover or sparks from occurring.

However, DC motors generally have a reactor 6 inserted as shown in Figure 1 for the purpose of improving the rectification function, and the time constant of the circuit is large. Means for detecting current have disadvantages in that it takes time to detect and cannot cope with flashovers and sparks. Furthermore, as shown in Figure 3, if the increase in current fluctuates to the extent that it does not reach the overcurrent detection set value _I1 , the DC motor will be operated in the field weakening region for a long time, and the rectification It also had the disadvantage of significantly deteriorating performance. FIG. 4 is a waveform diagram of the current in the armature circuit showing the first drawback, which is the detection time delay. When the voltage rise shown in FIG. 2 occurs at time t ₁ , the current finally reaches the overcurrent detection setting value at time t ₂ . The time between time t ₁ and t ₂ is 10 ms to 50 ms, although it varies depending on the circuit constants. Next, a detection time (approximately 20 ms) is required for the voltage detector 8 and the subtracter 10 to detect this, and a signal is output from the subtracter 10 for the first time at time _t3 . in this way,
It takes a considerable amount of time until the output voltage increases and a signal corresponding to the increase is output. Moreover, for example, in the conventional device that interrupts the armature circuit,
If the interruption is performed by a relay, the opening time is the period from time t ₃ to time t ₄ (approximately 50 m
s), and the time from time t ₄ to time t ₅ (approximately 50
ms). During this time delay, flashover and sparks cannot be prevented.

An object of the present invention is to eliminate the above-mentioned conventional drawbacks, and to provide a separately excited DC motor that can detect overcurrent without time delay and prevent flashover and sparks in the rotor. To provide protective equipment.

In order to achieve this object, the present invention provides a separately excited DC motor comprising an armature and separately excited field windings driven by a DC power supply, in which the output voltage of the DC power supply and the induced electromotive force of the separately excited DC motor are and a resistor for suppressing the armature current of the separately excited DC motor, and a circuit that connects the resistor when the value detected by the differential voltage detector exceeds a predetermined value. The invention is characterized in that it is provided with a protection means consisting of a switching element inserted into the opening/closing element.

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 5 is a circuit diagram of a protection device for a separately excited DC motor according to an embodiment of the present invention. In the figure, parts that are the same as those shown in FIG. 1 are designated by the same reference numerals, and description thereof will be omitted. 11 is a power supply voltage detector that detects the output voltage of the semiconductor rectifier 1; 12 is an armature 3;
An armature voltage detector 13 detects the voltage (induced electromotive force) between the brushes of It is a detector. The differential voltage detector 13 outputs an activation signal when the differential voltage is greater than or equal to a predetermined value. 14 is a shunt resistor, and 15 is a shunt circuit switch, both of which are connected in series to form a shunt circuit, and this shunt circuit is connected in parallel to the armature 3. 16 is a series resistor, 17 is a switch connected in parallel to the series resistor 16, and a parallel circuit of the series resistor 16 and switch 17 is connected in series to the armature 3. The switch 15 and the switch 17 are configured to be operated by the output signal of the differential voltage detector 13. Note that the switch 15 is always open, and the switch 17 is always closed.

Next, the operation of this embodiment will be explained with reference to the time charts shown in FIGS. 6a, b, and c. When the output voltage of the semiconductor rectifier 1 is at the normal voltage _V1 , the differential voltage detector 13 does not output an operating signal, the switch 15 is in an open state, the switch 17 is in a closed state, and the motor is in a closed state. Operated under normal conditions.
Now, if the output voltages of the semiconductor rectifiers 1 and 2 suddenly rise to voltage V ₂ at time t ₁ (Fig. 6a), the inductance of the separately excited field winding 5 in the field circuit is large. Therefore, the rise of the current is slow and there is also a delay in the field magnetic flux, so that the rise of the induced electromotive force generated in the armature 3 is delayed (Fig. 6a). Therefore, the induced electromotive force generated in the armature 3 and the semiconductor rectifier 1
The voltage difference between the output voltage and the output voltage becomes large, and an armature circuit current as shown in FIG. 3 or 4 tends to flow. Here, if the voltage difference is large and exceeds a predetermined value, the differential voltage detector 13 outputs an activation signal to the switches 15 and 17, and the switch 1
5 and 17 are activated at time _t2 with a slight time delay (Fig. 6c), the switch 15 is closed to connect the shunt circuit, and the switch 17 is opened to connect the series resistor 16.
Insert. Therefore, the transient overcurrent that attempts to flow into the armature circuit flows into the shunt circuit consisting of only the shunt resistor 14 (Fig. 6c), and at the same time, the
Since 6 is also introduced at the same time, it is rapidly attenuated (Fig. 6b). As shown in FIG. 6a, when the series resistor 16 is inserted at time _t2 , a voltage drop A shown by the dashed line occurs, and in the armature 3, the voltage _V1 before the power supply voltage rises and the induction It is possible to maintain a difference approximately equal to the difference with the electromotive force. and,
The induced electromotive force rises due to the increase in motor rotation speed due to the increase in voltage, and at the point when the difference with the power supply voltage becomes small, the output signal of the differential voltage detector 13 disappears.
As a result, the switch 17 is closed and the series resistor 16 is short-circuited, and the switch 15 is opened after a delay when the transient current at the time of the short-circuit returns to a steady state.

In this way, in this embodiment, the voltage difference between the power supply voltage and the induced electromotive force of the armature is directly detected, and accordingly, a shunt circuit is connected in parallel with the armature, and at the same time, a resistor is connected in series with the armature. By inserting it, it is possible to immediately detect a rise in the power supply voltage, protect the armature before the transient current reaches its peak value, and prevent sparks from occurring due to flashover.

FIG. 7 is a circuit diagram of a protection device for a separately excited DC motor according to another embodiment of the present invention. In the figure, the fifth
Components that are the same as those shown in the figures are given the same reference numerals and explanations will be omitted. The circuit configuration of this embodiment differs from the circuit configuration of the embodiment shown in FIG. 5 by adding a resistor 18 and a switch 19 connected in parallel to the resistor 18 in series with the armature 3. be. Switch 1
Like the switches 15 and 17, the switch 9 is operated (contact opening) by an operating signal from the differential voltage detector 13.

When the output voltage of the semiconductor rectifier 1 increases and the difference between it and the induced electromotive force of the armature 3 exceeds a predetermined value, the differential voltage detector 13 outputs an activation signal, and the switch 1
5 is closed, and switches 17 and 19 are opened. As a result, a shunt circuit is connected in parallel to the armature 3, and a resistor 16 and a resistor 18 are inserted in series with the armature 3. As a result, as in the embodiment shown in FIG. 5, the armature 3 can be protected and flashover and sparks can be prevented. When the induced electromotive force rises and the difference with the power supply voltage becomes small, the activation signal of the differential voltage detector 13 disappears, which first closes one of the switches 17 and 19 and closes one of the resistors 16 and 18. short-circuit, then close the other switch to short-circuit the other resistor, and finally switch 1
Open 5. The sequential operation of such a switch is
This can be easily done by using an appropriate timer.

In this embodiment, the voltage difference between the power supply voltage and the induced electromotive force of the armature is directly detected, and accordingly, a shunt circuit is connected in parallel to the armature, and at the same time, a resistor is inserted in series with the armature. Therefore, not only does it have the same effect as the previous embodiment, but it also divides the resistor inserted in series into the armature into two parts, so that when the inserted resistor is removed from the armature circuit, it is removed with a time delay. Therefore, the transient current at that time can be suppressed.

Although the above description is about the case where the separately excited DC motor is used as a vehicle electric motor, it is not limited to this, and any separately excited DC motor that is connected to a power source that causes considerable fluctuations in its voltage can be used. The present invention can be applied. Further, in each of the above embodiments, both a shunt circuit and a series resistor are used, but only one of them may be used. Further, although each switch is illustrated as a mechanical switch, it is of course possible to apply an electronic switch.

As described above, in the present invention, the voltage difference between the power supply voltage and the induced electromotive force of the armature is directly detected, and when this voltage difference exceeds a predetermined value, the protection means provided in the armature circuit is activated. Since it is activated, it is possible to immediately detect a rise in the power supply voltage, protect the armature before the transient current reaches its peak value, and prevent flashover and sparks from occurring.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional separately-excited DC motor protection device, Figure 2 is an output voltage waveform diagram of a semiconductor rectifier, Figure 3 is a current waveform diagram of an armature circuit, and Figure 4 is a diagram of a conventional device. FIG. 5 is a circuit diagram of a protection device for a separately excited DC motor according to an embodiment of the present invention; FIGS. FIG. 5 is a time chart explaining the operation of the circuit shown in FIG. 5, and FIG. 7 is a circuit diagram of a protection device for a separately excited DC motor according to another embodiment of the present invention. 1, 2... Semiconductor rectifier, 3... Armature, 5
...Separately excited field winding, 6...Reactor, 11...
...power supply voltage detector, 12...armature voltage detector,
13... Differential voltage detector, 14... Shunt resistor, 1
5, 17...Switch, 16...Series resistance.

Claims (1)

[Claims] 1. A separately excited DC motor comprising an armature and a separately excited field winding driven by a DC power source,
A differential voltage detection means for detecting a voltage difference between the output voltage of the DC power supply and the induced electromotive force of the separately excited DC motor, a resistor for suppressing the armature current of the separately excited DC motor, and the differential voltage detection means. 1. A protection device for a separately excited DC motor, comprising a protection means comprising a switching element that inserts the resistor into a circuit when a detected value exceeds a predetermined value. 2. Protection of a separately excited DC motor according to claim 1, wherein a series circuit of the resistor and the switching element is connected in parallel to an armature of the separately excited DC motor. Device. 3. Protection of a separately excited DC motor according to claim 1, wherein a parallel circuit of the resistor and the switching element is connected in series to an armature of the separately excited DC motor. Device.