JPS59132718A - Device for protecting separately-excited dc motor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protection device for a separately excited DC motor, and particularly to a protection device for a separately excited DC motor that is suitable for a device using a DC power supply with large fluctuations in output voltage.

The speed of a separately excited DC motor can be freely controlled without the need for additional equipment that occupies a large area due to wire tensioning. 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 a device for protecting the excitation DC motor in addition to the above is required to protect against a rise in the busy power supply voltage. Such a protection device includes a device 1 that detects overcurrent in the armature circuit and cuts off the armature circuit based on the detection, or 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, 1
This is a subtracter that subtracts the voltage detected by the voltage detector 8 from the reference voltage.

The operation of this conventional protection device will be explained with reference to voltage and current waveform diagrams shown in FIGS. 2 and 3. 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,
The output voltage of semiconductor rectifiers 1 and 2 changes from voltage vI to voltage V
! In this case, the armature current increases,
When this overcurrent occurs, a flashover occurs, which activates other installed protection devices and stops the motor.

ball. Further, even if a flashover does not occur, sparks are generated violently, resulting in severe wear of the brass tip. By the way, in the conventional device shown in FIG. 1, the output voltage of the voltage detector 8 increases in accordance with the 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. The current detection means used in this invention 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 does not reach the overcurrent detection set value I, the DC motor is operated in the field weakening region for a long time. It also had the disadvantage of significantly deteriorating rectification 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 t1, the current finally reaches the overcurrent detection set value at time t. Although it varies depending on the circuit constants,
The time between times t0 and t2 is 10m8 to 50m5.

Next, a detection time (approximately 20 m5) 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, in a conventional device that interrupts an armature circuit, for example, if the interrupt is performed by a relay, the time from time t to time 141 (approximately 50 m5), and the arc caused by the opening after opening. However, from time t4 to time 1.
1 time (approximately 50m5). and,
During this time delay, flashovers and sparks cannot be prevented.

An object of the present invention is to eliminate the above-mentioned conventional drawbacks, detect overcurrent without time delay, and protect separately-excited DC motors by preventing flashovers and sparks in the rotor. The equipment is provided.

To achieve this objective, the present invention detects the voltage difference between the output voltage of the DC power supply and the induced electromotive force of the motor, and when the voltage difference is greater than a predetermined value, the protection provided in the armature circuit is activated. It is characterized in that the means is actuated.

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
12 is a power supply voltage detector that detects the output voltage of the semiconductor rectifier L; 12 is an armature voltage detector that detects the voltage (induced electromotive force) between the brushes of the armature 3; 13 is a power supply voltage detector 11 and the armature This is a differential voltage detector that inputs the detection value of the voltage detector 12 and detects the difference voltage between the two. 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 the 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 is shown in Fig. 6(, ), Φ), (c) K
This will be explained with reference to the time chart shown. When the output voltage of the semiconductor rectifier 1 is at the normal voltage v1, no activation signal is output from the differential voltage detector 13, and the switch 15
The switch 17 is in an open state and the switch 17 is in a closed state, and the motor is operated in a normal state. Now, at time t, the output voltages of semiconductor rectifiers 1 and 2 suddenly rise to voltage V.

When K increases (Fig. 6 (a)), in the field circuit, the rise of the current is slow because the inductance of the separately excited field winding 5 is large, and there is also a delay in the field magnetic flux, and the armature 3 The rise in the induced electromotive force that occurs in this process is delayed (Fig. 6(a)).

Therefore, the voltage difference between the induced electromotive force generated in the armature 3 and the output voltage of the semiconductor rectifier 1 increases, and the 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 sends an activation signal to the switch 1.
5°17, and switches 15 and 17 are activated at time t with a slight time delay (Fig. 6(c)).
, the switch 15 is closed to connect the shunt circuit, and the switch 17 is opened to connect the series resistor 16. Therefore, the transient overcurrent that is about to flow into the armature circuit flows into the shunt circuit consisting of only the shunt resistor 14 (Fig. 6 (C)), and the series resistor 16 is also applied at the same time, so it is rapidly attenuated. (6th
Figure 6)). As shown in FIG. 6(a), when the series resistor 16 is inserted at time t, a voltage drop A shown by the dashed line occurs, and the voltage v1 in the armature 3 differs from that before the power supply voltage rises. A difference approximately equal to the difference with the induced electromotive force can be maintained. Then, the induced electromotive force rises due to the increase in motor rotation speed due to the rise in voltage, and when the difference with the power supply voltage becomes small, the output signal of the differential voltage detector 13 disappears, which closes the switch 17 and resists the series resistance. 16 is short-circuited, and the switch 15 is opened after a delay when the transient current at the time of this 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, a shunt circuit is connected in parallel to the armature according to As shown in Figure 7, it is possible to immediately detect a rise in the power supply voltage and protect the armature before the transient current -h reaches its peak value, thereby preventing flashovers and sparks. , is a circuit diagram of a protection device for a separately excited DC motor according to another embodiment of the present invention. In the diagram, the same parts as those shown in FIG. The circuit configuration of the example is such that a resistor 18 and a switch 19 connected in parallel to the resistor 18 are connected in series to the armature 3 in addition to the circuit configuration of the embodiment shown in FIG.

The switch 19, like the switches 15 and 17, is operated (contact opening) by the operating signal of the differential voltage detector 13.The output voltage of the O semiconductor rectifier 1 increases, and the induction of the armature 3 increases. When the difference with the electromotive force exceeds a predetermined value, an activation signal is output from the differential voltage detector 13, and the switch 15 is closed.
Open the switches 17 and 19. As a result, armature 3
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 flashovers 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.
This first closes one of the switches 17 and 19 to short-circuit one of the resistors 16 and 18, then closes the other switch to short-circuit the other resistor, and finally opens the switch 15. Such sequential operation of the switches can be easily accomplished by using a suitable 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. Since K, 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, 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.
The present invention can be applied to any separately excited DC motor connected to a power source whose voltage varies considerably. 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 flashovers and sparks from occurring.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a protection device for a conventional separately excited DC motor.
Fig. 2 is an output voltage waveform diagram of the semiconductor rectifier, Fig. 3 is a current waveform diagram of the armature circuit, and Fig. 4 is a current waveform diagram of the armature circuit explaining the time delay in detection and activation in the 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, and FIGS. 6(a), (b), and (c) explain the operation of the circuit shown in FIG. 5. The time chart and FIG. 7 are circuit diagrams of a protection device for separately excited DC motors 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, 15 , 17 ...
...Switch, 16...Series resistance. $7 -79-

Claims (1)

[Claims] 1. In a separately excited DC motor driven by a DC power source, a protection means provided in an armature circuit of the motor;
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 motor, and actuating the protection means when the value detected by the differential voltage detection means exceeds a predetermined value. 1. A protection device for a separately excited DC motor, comprising: output means for outputting a signal. 2. In claim 1, the protection means:
A protection device for a separately excited DC motor, characterized in that it is a shunt circuit consisting of a series circuit of a resistor and a switching element connected in parallel to the armature of the motor. 3. In claim 1, the protection means:
A protection device for a separately excited DC motor, characterized in that it is a parallel circuit of a resistor and a switching element connected in series to an armature of the motor.