CH625648A5 - Electronic supply device for a DC traction motor allowing rapid traction/braking and braking/traction transition - Google Patents

Description

625,648

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CLAIM Electronic device for supplying a DC traction motor comprising at least one separate excitation winding comprising, between a positive polarity terminal (5) and a negative polarity terminal (6) of a source of power supply, a first branch comprising the separate excitation winding (2) of said motor and a chopper (10) of the separate excitation current, a first freewheeling diode (11) being arranged at the terminals of said separate excitation winding (2), characterized in that the device further comprises, between said terminals (5,6), a second branch traversed by the armature current in traction mode and comprising in order, a traction thyristor (12 ), a main chopper (13), a traction diode (14) and the armature (4) of the motor and, bypass on said traction diode and the armature, a braking thyristor (15), the anodes of said thyristors (12,15), said main chopper (13) and said jitter diode tion (14) being on the side of said positive terminal, and a third branch comprising in order a recovery diode (16) and a second freewheeling diode (17), the cathodes of these two diodes (16,17) being on the side of said positive terminal (5), the anode of said recovery diode (16) being connected on the one hand to the cathode of said traction diode (14) and, on the other hand, to the cathode of said traction thyristor (12) via a braking diode (18) whose anode is connected to the anode of said recovery diode (16).

The present invention relates to an electronic device for supplying a DC traction motor comprising at least one winding, of separate excitation which allows an almost instantaneous transition from the traction state to the braking state with recovery and vice versa. require the use of electromechanical equipment.

We know that the traction-braking transition can be obtained either by inversion of the polarity across the armature or by inversion of the armature current. In the latter case, the polarity at the motor terminals keeps the same direction, as does the flux in the main poles. To operate the transition, it is therefore a question of reversing the armature current with respect to the flux generated by the inductor.

The traction motors are generally supplied either through a starting rheostat or via an electronic circuit comprising a chopper, the ignition and excitation of which are on command. Until now, it was necessary to control the cancellation of the motor current to authorize the traction-braking transition (or vice versa) because this transition which was made by means of contactors could only take place when the motor current was canceled. In classic systems, the transition was made after a delay of three to four seconds.

The device according to the present invention overcomes this easement. Indeed, the order of transition from traction to braking or from braking to traction is executed almost immediately (delay of the order of a millisecond) whatever the initial current in the motor.

The present invention relates to an electronic device for feeding an excitation direct current traction motor comprising a separate excitation winding and, where appropriate, an additional winding in series with the armature of the motor. It comprises between a positive polarity terminal and a negative polarity terminal of a power source, a first branch comprising the separate excitation winding of said motor and a separate excitation current chopper, a first wheel diode free being disposed at the terminals of said separate excitation winding, and is characterized in that the device further comprises, between said terminals,

a second branch traversed by the armature current in traction mode and comprising in order, a traction thy ristor, a main chopper, a traction diode and the motor armature and, bypass on said traction diode and in-5 duit, a braking thyristor, the anodes of said thyristors, said main chopper and said traction diode being on the side of said positive terminal, and a third branch comprising in order a recovery diode and a second freewheeling diode, the cathodes of these two diodes being on the side of said positive terminal, the anode of said recovery diode being connected on the one hand to the cathode of said traction diode and, on the other hand, to the cathode of said traction thyristor by means of a braking diode, the anode of which is connected to the anode of said recovery diode.

The invention will be better understood on studying the example given below with reference to the appended drawing, in which FIG. 1 represents an electronic diagram of the supply device and FIG. 2 represents a graph of the different orders given to the different components ordered and their states.

As can be seen in FIG. 1, this is the supply of a DC excitation motor 1 with compound excitation comprising a winding 2 of separate excitation, and a winding 3 in series with the armature 4 of the motor. . It should be noted that the operating principle would be identical in the case of a separately excited motor, the series 3 winding being to be deleted from the diagram. The engine 1 functions as an engine if it is used in traction and as a generator in case it is used in braking. In traction and in braking, the separately excited winding 2 is always traversed in the same direction. On the other hand, the current must pass through the armature and possibly the series excitation winding in a certain direction in traction and in the opposite direction in braking.

In connection with the supply line, terminals 5 (posi-35 tive) and 6 (negative) supply the potential used to supply the motor with traction or, on the contrary, serve to return the energy coming from motor 1 operating as a generator in the case of regenerative braking.

In derivation on terminals 5 and 6, there is a first branch 7, a second branch 8 and a third branch 9. Branch 7 comprises a separate excitation chopper 10 whose passing direction goes from terminal 5 to terminal 6 through the separate excitation winding 2 at the terminals of which is disposed a freewheeling diode 11 mounted in opposite direction to the chopper 10. The branch 8 comprises a traction thyristor 12 whose anode is disposed on the positive terminal side 5 , then a main chopper 13 whose main thyristor is disposed in the same direction as the traction thyristor 12, the point common to the main chopper 13 and to the traction thyristor 12 being referenced E; then a traction diode 14 arranged in the same direction as the traction thyristor 8 and separated from the main chopper 13 by the common point F; then optionally the series 3 excitation winding and in all cases the armature 4 of the motor 1. The common point of the traction diode 14 and of the motor 1 is the point A. 55 The point B is the terminal of the armature 4 which is in connection with the negative terminal 6. In derivation on FB is arranged a connection comprising a braking thyristor 15 whose anode is connected to F. The branch 9 comprises a recovery diode 16 and a wheel diode free 17 whose cathodes are on the side of the positive terminal 6c 5.

In the connection between the cathode of the freewheeling diode 17 and the anode of the recovery diode 16 are arranged two points C and D, point C being connected to point A of branch 8 and point D being connected to the anode of a braking diode 18, of which 65 the cathode is connected to point E of branch 8.

The system described so far allows the engine to operate in traction and in regenerative braking. For rheostatic braking, it can be added between point D and the

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terminal 6 of the braking resistors 19 in series with a rheostatic braking thyristor 20.

The operating principle is as follows:

In all cases, whether in traction or in braking, the separate excitation winding 2 of the motor is supplied with current by means of the chopper 10 and the freewheeling diode 11. The current always flows in the same direction in this winding 2.

In the case of traction, the traction thyristor 12 receives ignition pulses on its trigger while the braking thyristor 15 does not receive any. The main chopper 13 receives successive orders to let the current flow or to stop it. When in traction, the main chopper 13 conducts, the current comes from terminal 5, passes through the traction thyristor 12, the main chopper 13, the traction diode 14, the series winding 3 (possibly) and the armature 4 of the motor to close on terminal 6. In motor 1, we note that the current follows the direction from A to B. Still in traction, when the main chopper 13 goes out, the traction thy ristor 12 does not drives more; there can be no sudden cut in the current in the motor; the motor current tends to decrease and a circuit is provided to loop it on itself. To short-circuit the motor, the current launched in the motor always flows in the direction AB, borrows the freewheeling diode 17 of branch 9 and closes from C to A.

In the case of regenerative braking, the braking thyristor 15 receives ignition pulses on the trigger and the traction thyristor 12 does not receive ignition pulses on its own. The main chopper 13 receives passage or blocking orders.

When in regenerative braking, the main chopper 13 is not conductive, the current from terminal 6 flows through the motor in the direction from B to A, then the AC, CD connections then the recovery diode 16 before close on terminal 5. Thus the recovery current flows through the motor and the recovery diode 16. The electromotive force of the engine operating as a generator is then equal to the line supply voltage. This occurs at high speeds of rotation of the wheels driving the armature of the motor, the electromotive force of the motor is sufficient when empty and the motor adapts in recovery to the line voltage.

When in regenerative braking, the wheel speeds are low, the electromotive force of the engine operating as a generator is lower than the supply voltage. To allow the current to be established, the motor is short-circuited by switching on the main chopper 13 and the braking thyristor 15. The motor current goes from B to A, borrows C, D, the braking diode 18, E , the main chopper 13, F, the braking thyristor 15 and closes again at B. When the current again has reached a sufficient value, the main chopper 13 is cut, the current consequently cancels in the braking diode 18 and the braking thyristor 15 and circulates again with the desired value in the recovery diode 16.

In the case of rheostatic braking, a bipolar circuit breaker (not shown) disposed between the line and terminals 5 and 6 is open. When the main chopper 13 is made non-conductive, the ignition of the rheostatic braking thyristor 20 allows the passage of the motor current in the direction B to A, then A to C, then C to D, then from D to B through the braking resistors 19 and the rheostatic braking thyristor 20. When the main chopper 13 is made conductive, the apparent value of the braking resistor is reduced by short-circuiting the motor in the same way as that of regenerative braking. The braking-traction transition is first obtained by switching on the main chopper 13 and the braking thyristor 15 so as to cancel the current in the rheostatic braking thyristor 20. Then the main chopper 13 is turned off to extinguish braking thyristor 15.

In this device it can be noted that in no case should there be simultaneous conduction of the traction thyristor 12 and the braking thyristor 15 otherwise the terminals 5 and 6 would be short-circuited. In the device according to the present invention, the main chopper 13 is blocked for a duration of the order of at least a millisecond from the traction order 1 or the braking order in order to allow the blocking of the traction thyristor 12 and the braking thyristor 15 to ensure that they do not drive at the same time. Indeed, as the components are arranged in series with the main chopper 13, the extinction of the latter automatically causes the extinction of the traction thy ristor 12 (in the case of the traction-braking transition 15) and of the braking thyristor 15 (case braking-traction transition).

In Figure 2 we see a representation 21 of the traction state (high level 22) and the braking state (low level 23); the discontinuity 24 represents the order of passage under braking; discontinuity 25 represents the order of passage in tension.

The graph 26 represents in its high level 27 the ignition authorization of the traction thyristor 12 and in its low level 28 the ignition prohibition of the traction thyristor 12.

The pulses 29 represent the ignition pulses 25 sent to the trigger of the traction thyristor 12. The graph 30 represents in its high level 31 the authorization of ignition of the braking thyristor 15 and in its low level 32 the prohibition d ignition of the braking thyristor 15.

The pulses 33 represent the ignition pulses 30 sent to the trigger of the braking thyristor 15.

The graph 34 represents in its high level 35 the authorization of conduction of the main chopper 13 and in its low level 36 the prohibition of conduction of the main chopper 13. The duration of 36 is of the order of a millisecond allowing 35 the traction-braking or braking-traction transition.

Reference 37 represents the conduction state of the main chopper 13, the high level 38 signifying that the chopper 13 is driving, the low level 39 signifying that the chopper 13 is blocked.

The pulses 40 are clock pulses spaced 40 one to three milliseconds used to control the conduction of the main chopper as well as the synchronization of the pulses 29 and 33.

The start of the state of prohibition of the driver of the main chopper 13 is controlled by the order to switch to frei-45 swims 24 or the order to switch to traction 25. The cessation of the blocked state 39 of the chopper 13 cannot be commanded by the pulse 40 if the latter is understood for the duration of the slot 36.

The braking thyristor 15 is only turned on under two conditions, when its trigger receives the order and when the main chopper 13 is in conduction state. It only conducts when braking.

The traction thyristor 12 is also switched on only under these two conditions. It is only conductive in traction. 55 The traction-braking-traction transitions are almost instantaneous since in order to pass from one state to another, it suffices to switch off the traction thyristor or the initially conducting braking thyristor while maintaining the main chopper 13 in the blocked state. for a sufficient time, for example, a 60 millisecond.

The device according to the invention also has the great advantage of guaranteeing a loopback path with the current launched into the motor whatever its operating state, through the freewheeling diode 17 in traction and through the recovery diode 16 when braking. There is thus no risk of overvoltage due to a sudden cut in the supply circuit.

The applications are in the rail or road domain.

VS

2 sheets of drawings