JPH0213557B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stationary Leonard device in which the armature circuit of a DC motor is supplied from an AC power supply via a thyristor pure bridge.

In this type of static Leonard device, if a power outage occurs during regenerative braking of the DC motor, the thyristor pure bridge may fail in commutation and fail due to overcurrent, so some kind of protection is required. In particular, in a vehicle stationary Leonard system which receives power from an AC overhead line through a current collector, such protection measures are very important since power outages can often occur due to disconnection of the current collector.

Figures 1 and 2 show different embodiments of conventional stationary Leonard devices with such protection means.

In the case of Fig. 1, two sets of three-phase thyristor pure bridges REC1,
REC2 is connected, and both bridges are connected in antiparallel to each other. The armature of the DC motor M is connected to the DC output sides of both bridges via a DC reactor DCL and a high-speed shield breaker HB. When the DC motor rotates forward, the bridge REC1 performs a power running operation, and the bridge REC2 performs a regenerative control operation, while when the DC motor rotates in the reverse direction, the bridge REC2 performs a power running operation, and the bridge REC1 performs a regenerative braking operation. Bridge REC1 or REC during regenerative braking operation
2 is controlled in the inverse conversion region and performs commutation using the AC power supply voltage, so if a power outage occurs due to disconnection of current collector A, commutation will fail. Protection against commutation failure is provided by a high speed shunt breaker HB. This high-speed shield breaker HB has the drawbacks of being large and expensive, and is difficult to operate and is not suitable for applications with many operating circuits.

In the case of FIG. 2, only one set of thyristor pure bridge REC is used, and in its place an armature switching contactor K _A and a field switching contactor K _F are added. Field switching contactor is used to switch between forward and reverse directions of the motor.
This is done by field reversal by K _F , and the switching of the power running regeneration control of the motor is done by switching the armature polarity by armature switching contactor K _A. Since protection against commutation failure during regenerative braking is likewise provided by a high-speed shunt breaker HB, this case too has the same drawbacks as in Figure 1, but also requires an armature switching contactor. There is also a drawback.

High speed breaker in Figures 1 and 2
It is also possible to protect the vehicle with a fuse instead of the HB, but this method cannot be applied to stationary Leonard devices for electric vehicles because a single commutation failure will make the vehicle unable to run.

It is an object of the present invention to provide a stationary Leonard device that does not require high speed shunts to protect against commutation failure during regenerative braking.

The present invention will be described in detail below with reference to FIGS. 3 and 4.

According to Fig. 3, a current collector A, a breaker B, and an AC reactor are connected to a three-phase AC overhead line (not shown).
Two sets of three-phase thyristor pure bridge through ACL
REC3 and REC4 are connected, and both bridges are connected in antiparallel on the DC output side and connected to the DC reactor DCL.
and DC motor M via overcurrent relay OCR
is connected to the armature of In this case, according to the present invention, the bridge REC3 is used exclusively for power running, and the bridge REC4 is used exclusively for regenerative braking,
A current limiting resistor R _B is inserted and connected in series on both sides of the bridge REC4 dedicated to regenerative braking. The direction of rotation of the motor is switched by a field contactor _KF .

In both cases of forward rotation and reverse rotation, the power running operation is performed by the bridge REC3, and the regenerative braking operation is performed by the bridge REC4.

In the stationary Leonard device according to the present invention, even if a commutation failure occurs due to a power outage during regenerative braking, the short-circuit current flowing through bridge REC4 is limited to the value i _B = e _M /2R _B thanks to the current limiting resistor. (where e _M is the motor induced voltage). Therefore, it is not necessary to quickly disconnect the armature circuit using a high-speed circuit breaker as in the conventional case, and the armature current can be attenuated by slow operation. In other words, a contactor inserted in series with the armature circuit can be used to interrupt the armature circuit when commutation fails, and a high-speed interrupter is not required. Furthermore, as shown in FIG. 3, if the overcurrent relay OCR is used to disconnect the field, the above-mentioned special contactor becomes unnecessary. According to FIG. 3, the contacts of the overcurrent relay OCR are inserted in series in the common excitation current path of the forward rotation contact closing coil FC and the reverse rotation contact closing coil of the field contactor _KF . A discharge resistor R _F is connected in parallel to the field winding F.

Figure 4 shows the motor induced voltage e _M motor current i _B and field current i _f when commutation fails in the device shown in Figure 3.
A time course example is shown.

By the rotation direction switching circuit S, for example, the coil
FC is energized and the thyristor bridge REC
4 assumes that regenerative braking is being performed.
In this case, as is known, the bridge REC 4 is ignited in such a way that the motor current i _B is kept at a constant value I _M . According to FIG. 4, commutation failure occurs at time t ₀ ,
As a result of this, the motor current begins to increase.
At time _t1 , the overcurrent relay OCR is activated, its contacts are opened, and the current in the coil that has been energized until now is reduced to zero. As a result, the contacts of the field contactor are opened, but this opening is only performed at time _t2 , which is later than time _t1 . from time t ₁ to time
During t ₂ , the motor current i _B increases, but the value
Once it reaches e _M / _2RB , it remains at this value. When the contacts of the field contactor are opened at time t ₂ ,
The opening current i _f attenuates while flowing through the discharge resistance R _f . Along with this, the motor induced voltage decreases, and accordingly, the motor current i _B also decreases toward zero. As described above, according to the present invention, even if the opening is delayed, the motor current is limited by the current limiting resistor _RB , so that the thyristor element of the bridge REC4 can be protected.

With the bridge REC3 dedicated to power running and the bridge REC4 dedicated to regenerative braking, the switching time from power running to regenerative braking is sufficiently short, similar to the normal reverse parallel connection Leonardo. On the other hand, switching the direction of rotation, that is, switching the vehicle forward or backward, is done by field reversal, so the reversal time tends to be a little longer, but there is no need to rush forward or backward switching, so this is not a practical problem. do not have.

The best way to insert the current limiting resistor R _B into the bridge is to divide it equally into the positive side and negative side of the bridge REC4.
It is desirable to balance the voltage applied to the thyristor elements of REC3, but if there is no problem with the withstand voltage of the thyristor elements, it is okay to put them together on one side. Or, in some cases, Bridge REC4
The current limiting resistor may also be inserted separately into each arm, and in this case, the current limiting resistor also serves to suppress the commutation current.

[Brief explanation of drawings]

1 and 2 are connection diagrams showing different embodiments of a conventional stationary Leonard device, FIG. 3 is a connection diagram showing an embodiment of a stationary Leonard device according to the present invention, and FIG. 4 is a connection diagram of a stationary Leonard device according to the present invention. FIG. 3 is an explanatory diagram of the operation of the embodiment. REC3... Thyristor pure bridge exclusively for power running,
REC4...Thyristor pure bridge dedicated to regenerative braking, R _B ...Current limiting resistor, M...DC motor, F...
...field winding, R _F ...discharge resistance, K _F ...field contactor, OCR ...overcurrent relay.

Claims (1)

[Claims] 1 AC power is obtained from an AC feeder line through a current collector, and powering operation and braking operation are performed using a thyristor power conversion device interposed between this AC power source and the armature circuit of a DC motor for driving a vehicle. In the stationary Leonard device, the thyristor power conversion device is composed of two thyristor pure bridges connected in antiparallel to each other, one of the thyristor pure bridges is used for power running, and the other thyristor pure bridge is used for power running, regardless of the direction of travel of the vehicle. A stationary Leonard device characterized in that a field polarity switching means is provided for switching the direction of movement of the vehicle so as to be used exclusively for regenerative braking, and a current limiting resistor is inserted and connected in series only to the other thyristor pure bridge that is used exclusively for braking. .