JPS60128891A - Field control circuit of series motor - Google Patents

Abstract

PURPOSE:To reduce the size and to eliminate contacts of a field weakening unit by connecting a semiconductor switch which can control the bidirectional energizations in parallel with part of a branch resistor connected in parallel with a field winding. CONSTITUTION:AC power supplied from trolley wires is collected from a pantograph 1, and supplied through a transformer 2 and a diode rectifier 4 to a motor armature 6 and a field winding 7. A branch resistor 8 formed by connecting in series resistors 81, 82 is connected in parallel with the winding 7 to branch the pulsating component of a pulsating DC current to the resistor 8. Thyristors 21, 22 are connected in parallel with the resistor 82, controlled to fire, thereby performing a field weakening control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a field control circuit that weakens the field of a DC series motor driven by DC power obtained by rectifying AC.

[Prior art and its problems]

DC series-wound motors are often used to drive electric cars because they can produce large torque at low speeds, but recently, AC power supplied from overhead wires, such as the Shinkansen, is being used to power the cars. A so-called AC electric car is used, which uses a device to convert DC power into DC power and feed it to an electric motor.

Conventional problems will be explained below using this AC electric vehicle as an example.

Figure 1 is a main circuit connection diagram of a conventional AC electric car. In Figure 1, AC power from the overhead wire is collected by a pantograph 1, and flows to the rails via a transformer 2 and wheels 3. It has become.

The AC power transformed by the transformer 2 is converted into DC power by a diode rectifier as a semiconductor converter 4, and then is connected to a motor armature 6 via a DC reactor 5.
The current flows to the motor field winding 7 connected in series to the armature 6. This armature 6 and field winding 7 are connected in series to form a series motor. Note that a shunt resistor 8 is connected in parallel to the field winding 7. In an actual electric car, 1
A plurality of series motors are connected to the set of pantographs and the transformer, and the transformer 2 is equipped with a tap changer, and is further provided with a rectifier consisting of a pure bridge or a mixed bridge of thyristors instead of the diode rectifier 4. Although the voltage applied to the winding motor can be adjusted, it is omitted to avoid complicating the diagram.

The DC voltage output by the diode rectifier 4 is a pulsating voltage because it rectifies AC. Therefore, in order to suppress the pulsation of the current flowing through the armature 6, a DC reactor 5 is provided between the diode rectifier 4 and the series-wound motor. The pulsating current whose pulsation rate has been reduced by this DC reactor 5 flows through the armature 6 and field winding 7 of the series-wound motor, but the pulsating current flowing through the field winding 7 has a negative effect on the rectification of the motor. Therefore, a shunt resistor 8 is connected in parallel to the field winding 7.
is connected to shunt resistor 8 to shunt the pulsating portion of the pulsating current, thereby smoothing the current flowing through field winding 7. At this time, the pulsating current flowing through the shunt resistor 8 is approximately 10
% or less. That is, the first
In the figure, the armature current Im flowing through the armature 6 is divided into a smooth field current If flowing through the field winding 7 and a pulsating shunt current 1r containing a slight DC component flowing through the shunt resistor 8.

FIG. 2 is an operating waveform diagram of each part in the main circuit connection shown in FIG. 1, and FIG. It shows that there is. Fig. 2 (c4 is the field current If flowing through the field winding 7, which is a smooth DC current with pulsation removed by the shunt resistance. Fig. 2 (c) shows the field current If flowing through the field winding 7. 8
The shunt current Ir flowing through the circuit is a pulsating current that includes a direct current component and changes in positive and negative directions. The sum of the field current If shown in Fig. 2 (C) and the shunt current 1r shown in Fig. 2 (C) is
This is the armature current Im shown in a). 2) is a shunt voltage Vr that is applied across the shunt resistor 8, and is a pulsating voltage that includes a direct current component and changes from positive to negative, similar to the shunt current Ir.

It is well known that weakening the field of a DC motor increases the rotational speed, and even in AC electric cars, the field of the series-wound motor is weakened to enable high-speed operation.

Figure 3 is a field weakening connection diagram of a conventional AC electric car,
It is capable of two-stage field weakening. In FIG. 3, AC power from the overhead wire is collected by a pangraph 1 and flows to the rails via a transformer 2 and wheels 3. The DC power transformed by the transformer 2 and rectified by the diode rectifier 4 flows through the DC reactor 5 to the TA machine armature 6, and then to the motor field winding 7 connected in series and this field winding 7. The current flows through the shunt resistor 8 which is connected in parallel.

Here, the role of the DC reactor 5 and the shunt resistor 8 is the first
As explained in the figure.

In the conventional example of field weakening shown in Fig. 3, field winding 7, J4
In addition to the parallel connection circuit with the field resistance 8, two series connection circuits of a contactor and a field weakening resistance are connected in parallel. Normally, both contactors 11 and 13 are operated in an open state, but when you want to weaken the field, that is, when you want to run at high speed, the contactor 11 and 13 operate in an open state.
1 is closed, the shunt resistor 8 and the field weakening resistor 12 are connected in parallel to the field winding 1llIj17.
Since part of the current that should flow through the field winding 7 is shunted to the field weakening resistor 12, the series current am enters a field weakening state and its speed increases. Furthermore, contactor 1
If 3 is also closed, part of the field current will also flow through the field weakening resistor 14 (5), further weakening the field and increasing the speed.

FIG. 4 is a speed/torque characteristic diagram, in which the horizontal axis represents the rotational speed of the series-wound motor, and the vertical axis represents the torque of the motor. In FIG. 4, curve A1 is the speed/torque characteristic curve of the series motor when field weakening is not performed, that is, when contactors 11 and 13 in FIG. 3 are both open, and curve A2 is the first stage weakening. Curve A3 shows the speed/torque characteristics of the series motor in the field state, that is, when the contactor 11 is closed and the contactor 13 is open, and the curve A3 shows the speed and torque characteristics of the series motor in the second stage weakening field state, that is, when both the contactors 11 and 13 are closed. It is a curve. Curve B is a load speed-bone torque characteristic curve and corresponds to the running resistance of the electric vehicle. Therefore, when the series motor is not weakening the field, this motor is balanced at the intersection of curve A1 and curve B, so the rotation speed at that time is N1, but in the first stage field weakening state. , the balancing point moves to the intersection of curve A2 and curve B, and the rotational speed at that time increases to N2. Furthermore, in the second stage field weakening state, the speed N3 at the intersection of curve A3 and curve B
rise to

(6) In other words, the rotation speed can be increased as shown in Figure 4 using the conventional field weakening circuit shown in Figure 3, but if you try to increase the number of stages of field weakening, you will need to use the same number of contactors as the number of stages. Since field weakening resistance is required, the circuit becomes complicated and the device becomes large, which is a major drawback for electric vehicles where installation space is limited. Furthermore, since a contactor is used, maintenance and inspection work is required, and there are various drawbacks, such as the inability to continuously control field weakening.

[Purpose of the invention]

The present invention provides a field control circuit for a series-wound motor that can continuously weaken the field of a DC series-wound motor driven by DC power obtained by rectifying alternating current using a small device that does not require maintenance or inspection. The purpose is to

[Key points of the invention]

This invention provides that when a shunt resistor is connected in parallel to the field winding of a DC series motor driven by DC power obtained by rectifying AC, the back pulsating current flowing through the armature of the motor is mostly flows through the shunt resistor, and the current flowing through this shunt resistor pulsates in positive and negative directions at a frequency higher than the frequency of the AC power supply (for example, twice the frequency of the power supply in the case of single-phase full-wave rectification). A semiconductor switch that can control current flow in both directions is connected in parallel to a portion of the shunt resistor, and by controlling this semiconductor switch, a portion of the armature current is transferred to this semiconductor. This is intended to perform field weakening control of the DC series motor by shunting the current to the switch.

[Embodiments of the invention]

FIG. 5 is a main circuit connection diagram showing an embodiment of the present invention, and the content of the present invention will be explained in detail with reference to FIG.

This Figure 5 shows the case of an AC electric car as in the conventional example described above, and means for controlling the DC voltage applied to the DC series motor (for example, a tap changing device of a transformer or a rectifier configured with a thyristor). As in the conventional example, the illustrations (e.g.) and the connection of multiple electric motors in series or parallel are omitted to simplify the illustration.

In FIG. 5, AC power supplied from the overhead wire is collected from a pantograph 1 and flows to the rails via a transformer 2 and wheels 3. The AC power transformed by the transformer 2 is rectified by the diode rectifier 4, and flows through the DC reactor 5 to the motor armature 6 and the motor field winding 7 connected in series thereto. A resistor 8 is connected in parallel to this field winding @7.
A shunt resistor 8 formed by connecting transistors 1 and 82 in series is connected, and the pulsating portion of the pulsating direct current is shunted to this shunt resistor 8, as in the conventional example already described.

In the embodiment of the invention, parallel thyristors 21 and n, which are connected in antiparallel to each other, are connected in parallel to a resistor 82, which is part of the shunt resistor 8 mentioned above.

By controlling the firing of either or both of the parallel thyristor 21 and ρ, field weakening control of the DC series motor is coupled.

FIG. 6 is an operational waveform diagram of the embodiment shown in FIG. 6th
Figure (e) shows the voltage waveform of the field winding @7 when both the above-mentioned parallel thyristor 21 and ρ are non-conducting, and this is equal to the voltage across the shunt resistor 8. In other words, this Figure 6 (E)
The voltage Vr shown in (9) in FIG. 2 is the same as the voltage Vr shown in (9) in FIG. The difference between the positive part and the negative part of the waveform of this shunt voltage Vr is the average value Vf of the field voltage. Field winding 1i! 7, a field current If, which is the average field voltage Vf divided by the resistance of the field winding 7, flows.

FIG. 6(f) shows the voltage waveform Vrx when the parallel thyristor 21 and ρ are controlled to fire, and the parallel thyristor 2
1 is when the period α1 is conductive at the forward voltage, and the other parallel thyristor 4 is also conductive for the period α1 at the forward voltage, as shown in FIG. 6(G).
is the waveform of the current ■1 flowing through the parallel thyristor 21 when performing the above-mentioned ignition control, and FIG. 6 (7) is the waveform of the current ■2 flowing through the parallel thyristor 22. During the period when n is conducting,
The parallel thyristors 21 and n have currents ■1 and ■, respectively.
i is divided.

As shown in FIG. 6(f), the difference between the positive part and the negative part of the voltage waveform Vrx is the average field voltage Vf1, and this average field voltage Vfx is equal to the conduction period α1 of the parallel thyristor 21 and the parallel thyristor n If you change the conduction period of (10), you can change it from 屹, so the field? The E'j'wL flow can be controlled to a desired value.

Among the resistors 81 and 82 forming the shunt resistor 8, the resistor 81 is not connected in parallel with the parallel resistance 21 and 22.
If the resistance value of is set to a very small value, the field winding *h
7 can be brought into a short-circuited state, so it is an effective means to eliminate when the wheels of an electric vehicle spin or slide. Furthermore, if the resistance value of the above-mentioned resistor 81 is selected to correspond to the maximum field weakening rate of the series motor, the parallel thyristor 2
The conduction angle control range of 1 and n can be expanded.

FIG. 7 is a correlation diagram between field voltage and field ratio, where the horizontal axis is the field voltage and the vertical axis is the field ratio, that is, VL43 & child current I.
The ratio of field current If to m is expressed. When the parallel thyristor 21 and n are non-conducting, the field voltage is Vf and the field ratio is the maximum value -, but the parallel thyristor 21
As the field voltage decreases due to the ignition control of and 22, the field ratio also decreases, indicating that the field becomes weaker.

FIG. 8 is a partial circuit diagram showing another embodiment of the present invention, showing only the circuit portion connected in parallel to the DC series motor and its field winding; the other portions are shown in FIG. 5. Since it is the same as the embodiment shown in , illustration is omitted.

In FIG. 8, rectified DC power flows through a DC reactor 5 to a motor armature 6 and a motor field winding 7 connected in series with the motor armature 6. is a shunt resistor 8 formed by connecting resistors 81 and 82 in series.
are connected in parallel.

Furthermore, since a triac 6 that can control energization in both directions is connected in parallel to the resistor 82, which is a part of the shunt resistor 8, the armature current is shunted to the triac 5 to lower the field ratio and weaken the field. can be realized.

When connecting multiple series-wound motors in series, the armatures are connected in series, the field windings are also connected in series, and the armatures and field windings connected in series are connected in series. Since this is common, the embodiment of the present invention shown in FIG. 5 or 8 can be applied as is by treating a plurality of series-connected field windings as one set of field windings.

〔Effect of the invention〕

In this invention, a semiconductor switch capable of controlling current flow in both directions is further connected in parallel to a part of the shunt resistor connected in parallel to the field winding of a DC series motor obtained by rectifying alternating current, and this semiconductor switch is used to control the field winding. Since the current is shunted, the field weakening device is made smaller and non-contact, eliminating the need for maintenance and inspection and requiring less space for installation.

Furthermore, the semiconductor switch has the effect of making field weakening control stepless. Furthermore, even if the wheels of an electric vehicle spin during power running or skid during braking, the semiconductor switch can be controlled to reduce the torque of the electric motor, quickly eliminating the slip or skidding. have

Furthermore, if the resistance value of the portion of the shunt resistance where the semiconductor switch is not connected in parallel is selected to a value commensurate with the maximum field weakening rate of the series-wound motor, the conduction angle control range of the semiconductor switch can be expanded. , (13) It also has the effect of allowing more stable control.

I also have it.

[Brief explanation of drawings]

Figure 1 is a main circuit connection diagram of a conventional AC electric vehicle;
The figure shows an operating waveform diagram of the conventional example shown in FIG. FIG. 3 is a field weakening connection diagram of a conventional AC electric vehicle, and FIG. 4 is a speed/torque characteristic diagram of the conventional example shown in FIG. FIG. 5 is a main circuit connection diagram showing an embodiment of the present invention, and FIG. 6 is an operation waveform diagram of the embodiment shown in FIG. FIG. 7 is a correlation diagram between field voltage and field ratio, and FIG. 8 is a partial circuit diagram showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Pantograph, 2...Transformer, 3...Wheel, 4...Diode rectifier, 5...DC reactor, 6...Motor armature, 7...Motor field winding line,
8...Shunt resistance, 11.13...Contactor, 12.1
4... Field weakening resistance, 21.22... Parallel thyristor, 5... Triac, 81.82... Resistance. (14) Figure 1 Figure 2 ← 7, Figure 4 Pregnancy (L + N) ~ノ ++J -ノ Figure 8-! vlG-

Claims (1)

[Claims] A series-wound motor in which a shunt resistor is connected in parallel to the field winding of the series-wound motor, and DC power obtained from a semiconductor converter connected to an AC power source is applied to the series-wound motor via a DC reactor. 1. A field control circuit for a series-wound motor, characterized in that, in the drive circuit, a semiconductor switch capable of controlling energization in both directions is connected in parallel to the shunt resistor.