JPH0449360B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a control method for a motor generator, and particularly to a control method suitable for preventing electric shock due to residual voltage in an armature.

[Background of the invention]

Motor generators (hereinafter abbreviated as MA) are often used as auxiliary power supplies for trains and other vehicles. MA circuits, especially those with large capacity, have a configuration as shown in Figure 1. In the figure, 1 is a power supply, 2 is a pantograph, 3 is a disconnector, 4 is a circuit breaker, 5 and 6 are armatures, 7 is a compensation winding, 8 is a commutator pole, 9 is a series winding field, and 10 is a field 11 is a shunt field, 12 is a backflow blocking diode, and 13 is a generator.

Now, pantograph 2 is on MA by the driver.
When a command to start operation is issued, the circuit breaker 4 closes and current flows from the power supply 1 through the pantograph 2 and the disconnector 3 to the armatures 5 and 6, the series field 9, and the shunt field 11. 5 and 6 start rotating. When the armatures 5 and 6 rotate, the generator directly connected to them also rotates, and the necessary power can be generated. At this time, the armatures 5 and 6 rotate so as to generate back electromotive forces E _M1 and E _M2 so that no more current than necessary to rotate the load flows into the armature. In a steady operating state, the back electromotive forces E _M1 and E _M2 together reach a value almost equal to the power supply voltage.

Next, assume that an MA operation stop command is issued. The circuit breaker 2 is opened, and power supply voltage is no longer applied to the motor. However, due to the inertia of the electric motor, it usually continues to rotate for more than ten minutes after receiving a stop command. Due to the rotation, a field current i _f flows using the back electromotive force E _M2 as a power source, and as a result, the back electromotive force continues to be generated even though it is attenuated.

Now, let's consider how the MA is handled as being opened by maintenance personnel operating a disconnector. When a failure occurs in the MA, the disconnector is opened to release the MA.

At this time, if the electric motor continues to rotate due to inertia, even if the disconnector is opened, a counter electromotive force will be generated for more than ten minutes as described above. If you accidentally touch the circuit, you may get an electric shock and die. In particular, if the power supply voltage is as high as 3000V, the back electromotive force is almost the same, so the danger is great.

There are two possible solutions to this problem:

First, as shown in FIG. 2, there is a method of providing a shunt field shorting switch 14. Since the ampere-turn of a shunt field is sufficiently larger than that of a series winding field, the idea is to eliminate the shunt field.
The field current i _f1 due to the back electromotive force E _M2 bypasses the shunt field, but the shunt field circuit has a time constant, e.g.
Since it takes about 0.3 seconds, it takes time for the initial field current i _f0 to decay, and even if the shunt field current reaches OA, a back electromotive force remains as a residual voltage due to the no-load saturation characteristics of the motor. For example, current voltage
For 3000V, 110KVA MA, residual voltage is 500V
It also becomes. It can be said that there is still a sufficient risk of electric shock.

The second method is to provide an armature shorting switch 16, as shown in FIG. This is a method in which the armatures 5 and 6 generating back electromotive force are short-circuited by an armature shorting switch 16 via a limiting resistor 15 to eliminate the generated voltage. Although this method can completely eliminate the generated voltage, it requires the capacity and insulation of the armature shorting switch. In other words, this is because a voltage generation source equal to the power supply voltage is short-circuited with a resistor. In this case, the _shunt field current is
Since i _f also leaks, it will take time for it to decay. Therefore, it cannot be said that this is a practically good method.

[Purpose of the invention]

An object of the present invention is to provide a control method that quickly attenuates the back electromotive force generated by a motor rotating due to inertia.

[Summary of the invention]

The key point of the present invention is to use the back electromotive force generated by the motor as it rotates due to inertia as a power source, and apply reverse excitation to its own shunt field to eliminate the field magnetic flux and quickly eliminate the back electromotive force. The goal is to cause it to decay.

[Embodiments of the invention]

An embodiment of the present invention will be described based on the drawings.

FIG. 4 is an MA circuit diagram showing an embodiment of the present invention.

Compared to FIG. 1, the field resistor 10 is divided into two parts 15A and 15B, and field changeover switches 17 and 18 that operate in conjunction with the disconnector 3 are provided.

In the steady operating state, a field current in the direction indicated by i _f0 flows through the shunt field 11. Now, when the disconnector 3 is switched to the ground side, that is, when the MA is opened, the field changeover switches 17 and 18 are turned on in conjunction with this. In this case, the back electromotive force is used as a power source, and a current in the direction indicated by the field current i _f1 is caused to flow through the shunt field 11.

FIG. 5 shows an equivalent circuit at this time. If we consider an MA with a power supply voltage of 3000V and a capacity of 110KVA, the back electromotive force is 1500V in one armature, that is,
E becomes _M2 . The impedance of the shunt field 11 is
200H, internal resistance 609Ω, field resistance 15A, 15B impedance is 200Ω. Also, the initial field current
i _f0 becomes 1.5A.

FIG _. 6 shows the results of simulating the time course of E _M2 and if using these circuit constants. Even when the field current i _f is 0A, a residual voltage of 500V remains in one armature, and twice as much as 1000V remains in the motor. Furthermore, due to reverse excitation, the field current i _f0 has a reverse polarity. Thus, it can be seen that the back electromotive force E _M2 completely decays in 2 to 3 seconds after the field changeover switch is turned on.

In this way, the counter electromotive force, which conventionally required more than ten minutes to decay, now takes only a few seconds.

〔Effect of the invention〕

According to the present invention, since the back electromotive force generated due to inertia can be quickly dissipated,
It is possible to prevent electric shock to maintenance personnel, etc.

[Brief explanation of the drawing]

Figure 1 is a conventional MA circuit diagram, Figures 2 and 3 are MA circuit diagrams as an improvement plan, Figure 4 is an MA circuit diagram of an embodiment of the present invention, and Figure 5 is a shunt field circuit diagram. FIG. 6 is a characteristic diagram of the simulation result. 11...Shunt field, 5,6...Armature, 15A, 1
5B... Field resistance, 17, 18... Field switching switch.

Claims (1)

[Scope of Claims] 1. A power switch that opens and closes a power supply and a main circuit, an armature connected in series with the power switch, a series field connected in series with the armature, and a power supply switch connected to the armature in series. In a method of controlling a motor generator consisting of shunt winding magnets connected in parallel, when the power supply switch is opened, the residual voltage of the armature is used as a power source, and the residual voltage that had been flowing in the shunt winding field up to that point is used as a power source. A method for controlling a motor generator, characterized in that the shunt field is reconnected using a reconnection switch so that a current of opposite polarity to the field current flows. 2. A method for controlling a motor generator according to claim 1, characterized in that the power supply switch and the switching switch are linked.