DE3338318A1 - DC actuation circuit for electrical vehicles having automatic field attenuation - Google Patents

Abstract

In this DC actuation circuit for drives in short-distance vehicles having two and more DC series-characteristic motors (4, 10) connected in parallel, as the motor speed rises automatic field attenuation takes place in travel mode whilst in brake mode the field attenuation can be controlled. Since inadmissibly high differences in the loading of the motors can arise due to machine tolerances, the armature currents of the motors (4, 10) which are connected in parallel are adjusted to be the same by influencing the exciter currents. This adjustment acts in the timing range of the clocking period in which the field currents are freewheeling. The adjustment facility for a control is provided by means of series field resistors (14, 15) which are located in series in the field windings (17, 19) and can be bypassed by means of control thyristors (18, 20). When the armature currents are identical, both thyristors (18, 20) are fired at the start of the freewheeling of the field and in the event of deviations one of the thyristors is not fired or fired late as a result of which the corresponding field current decays more quickly and a field current is produced which is smaller on average. <IMAGE>

Description

DC chopper circuit for electric vehicles

with automatic field weakening The invention relates to a DC converter circuit for electric vehicles with automatic field weakening according to the preamble of claim 1.

Such a DC chopper is from Brown Boveri-Mitteilungen 12-78, P. 777-785 1110 years of the BSC DC power controller for local transport vehicles "and the RBC publication No. D VK 900111 D "the BBC DC chopper equipment for the runway car M / N "known.

The drive circuit for a direct current series motor the field weakening operation - without the usual additional effort for resistors and Contacts or even your own springs - automatically set by the fact that the current commutating from the armature to the field in the free-wheeling circuit with increasing Modulation continuously decreases until it reaches a fixed setting, the motor beneficial smallest pathogen level.

A direct parallel connection of motors to a DC power controller is not possible with the help of this known circuit, because machine tolerances, which may be intensified by anchor reactions, inadmissible high Differences in engine loads can arise.

On this basis, the invention is based on the object of a DC chopper circuit for electric vehicles with automatic field weakening of the aforementioned Specify the type that is suitable for supplying motors connected in parallel.

This task is achieved by the features identified in claim 1 qet < solved.

The advantages that can be achieved with the invention are, in particular, that the armature currents of the motors connected in parallel by influencing the excitation currents can be regulated for equality and are therefore not inadmissible despite machine tolerances can set high differences in the engine load.

Advantageous embodiments of the invention are set out in the subclaims marked.

The invention is illustrated below with reference to the in the drawing embodiment explained.

In the figure, a circuit for parallel operation of motors is on a DC chopper with which starts automatically when driving or when braking controlled field weakening shown. At the positive pole 1 of an energy source (contact line network) an input filter choke 2, a first Fshrscealter, are connected in series F1, an ignitable and erasable electronic switch 3, a second Driving switch F2 (it also serves as brake switch B2) and a first direct current series motor 4 with its armature winding 5. The armature winding 5 is on the other hand via the series connection a first series diode 6, a third drive switch F3 (which is also used as Brake switch B3 is used), a motor smoothing throttle 7, and further travel switches F6 and F7 connected to the negative pole of the energy source.

Located at the connection point between switch F2 / B2 and armature winding 5 a second series diode 9, the other hand with the armature winding 11 of a second DC series motor 10 is connected. The armature winding 11 is with her Another terminal connected to the connection point of diode 6 and switch F3 / B3.

Between the common connection point of filter throttle 2 / drive switch F1 and the negative pole 8 of the energy source, an input filter capacitor 12 is connected.

At the connection point of electronic switch 3 and switch F2 / B2 is another drive switch F8, which has an armature freewheeling diode 13 with a first resp.

second field resistor 14 or 15 and a field freewheeling diode 16 is connected. The field winding 17 of the are connected to the first Fendvor resistor 14 first motor 4 and a first control thyristor 18 connected. On the second field resistor 15 are the field winding 19 of the second motor 10 and a second control thyristor 20th

The field windings 17, 19 are on the other hand at the connection point the drive switch F6, F7 connected, while the control thyristors 18, 20 and the diode 16 on the other hand at the connection point of the smoothing choke 7 and the drive switch F6 lie.

To carry out the braking operation is between the connection points of travel switch F1 / electronic switch 3 and travel switch Fg / diode 13 a first Brake switch B1 provided. Further brake switches B or Bs (which are used when changing direction also serve as driving switch F4 or F5) are located between the connection points Switch F2 / electronic switch 3 and armature winding 5 / diode 6 or the connection points Switch F3 / smoothing choke 7 and armature winding 11 / diode 9.

A brake thyristor 21 is on the one hand via a brake switch B on the negative pole 8, on the other hand via a braking resistor 22 for resistance braking operation and a feedback diode 23 at the connection point of the FaFr switch F1 and the electronic Switch 3 connected.

The brake switch B6 also applies the negative pole 8 to the connection point from switch F2 / B2 and electronic switch 3.

The connection point of braking resistor 22 and regenerative diode 23 is connected to a mains protection resistor 24 and a quenching diode 25. The network protection resistor 24 is on the other hand at the connection point of the drive switch F6 / F7 and the diode 25 on the other hand at the connection point of diode 13 and drive switch Fq.

A composite brake resistor 26 is arranged parallel to the travel switch F6.

The switches F2, F3, B4, Bs are also used to change direction of motors 4, 10. When the motors are turned clockwise (this corresponds to e.g. the forward movement of a vehicle) are the driving switches F1, F21 Fq, F6, F7, F8 closed, while the brake switches B1, B4, B5, B6 opened stay. in the Conversely, the aforementioned drive switches remain in braking mode opened while the mentioned brake switches are closed. When turning of the motors in an anti-clockwise direction (this corresponds, for example, to driving backwards of a vehicle) the function of switches F2, F3, B4, B5 changes, i.e. the Travel switches F21 F3 become brake switches B2, B3 and brake switches B4, B5 become driving switches F4, Fg. When the motors are turned counterclockwise the drive switches F1, Fa, Fg, F6, F7, F8 are closed while driving the brake switches B1, B2, B3, B6 remain open. The other way round remains in braking mode the mentioned Fahrscha) .ter open, while the-mentioned brake switch closed are.

The circuit concept of the one that starts automatically when the vehicle is in motion Field weakening is based on the fact that in the armature freewheeling circuit - executed with the armature freewheeling diode 13 - pulsating currents with the same peak values as train in the anchor circle. This process is only possible if the one required for it Time is available. If the modulation of the DC chopper is close of 1 (full modulation), the time for the current build-up is no longer sufficient. The peak value of the current in the armature freewheeling circuit falls compared to the peak value the anchor currents. Over the freewheeling circuits of the motor fields - carried out with the Field freewheeling diode 16 or the control thyristors 18, 20 - results in a peak value rectification the current pulses of the armature freewheeling circuit.

This is how the current peak values of the armature freewheeling circuit arise the very well smoothed field currents, their size depending on the current peak values can be controlled in the armature freewheeling circuit.

Even though the motor fields are in a shunt branch, so retains the arrangement in the entire working area its series connection characteristics. The circuit with its own continuous field weakening process in contrast to conventional field monitoring a stepless operation without restriction in the entire traction speed range of a DC vehicle.

In detail, as mentioned, the driving switches F1, F2, F3, F6, F7 and F8 closed, all other switches are open. With controlled electronisohem switch 3 results in an armature current flow from the positive terminal 1 via the Input filter choke 2, the drive switch F1, the electronic switch 3, the Driving switch F2, the two parallel series connections armature winding 5 / series diode 6 or series diode 9 / armature winding 11, the motor smoothing choke 7 and the two Drive switch F6, F7 to negative pole 8.

At the same time, as a result of the current storage effect of the inductances flow of the field windings excitation currents, i.e. field freewheeling currents from the field winding 17 via the field resistor 14, the field freewheeling diode 16 and Hen drive switch F6 to the winding 17 or from the field winding 19 via the field resistor 15, the Diode 16 and switch F6 back to winding 19. These excitation currents flow with blocked thyristors 18, 20.

In this time range of the cycle period in which the field currents are free-running are, the armature currents of the motors 4, 10 connected in parallel are influenced by them the excitation currents regulated for equality. The setting option for the regulation is through the bridged with the control thyristors 18, 20 Feldvorwiderstän the 14, 15 created. If both armature currents are equal will both Thyristors 18, 20 ignited at the beginning of field freewheeling, with excitation currents then from winding 17 via thyristor 18 and switch F6 back to winding 17 and from winding 19 via thyristor 20 and switch F6 to winding 19 flow back.

To detect the armature currents, measuring devices 27, 28 are in the Line sections switch F2 / B2 - armature winding 5 - diode 6 - switch F3 / B3 and switch F2 / B2 - diode 9 - armature winding 11 - switch F3 / B3 provided. the Armature currents flowing through armature winding 5 and 11 are denoted by 1A1 and 1A2, respectively. If the two armature currents 1A1, IA2 deviate from one another, one of the control thyristors is activated 18, 20 not or delayed compared to the other thyristor, whereby the corresponding excitation current (field current) via the corresponding field resistor flows, which decays faster and an on average smaller excitation current develops results. The field freewheeling diode 16 does not provide a freewheeling path in any case fired thyristors safely.

The control of the control thyristors 18, 20 is possible as follows: If a slight deviation in the armature currents is permitted, a simple one is used Three-point control can be used depending on the current difference IA1 2 IA2. However, it is An exact regulation is also possible by placing the converter valves within the possible ignition time one of the ignition pulses is time-controlled in relation to the earliest possible ignition point is delayed.

There is no separate extinguishing device for the control thyristors 18, 20 necessary, they are in every clock period during the excitement (ufmagnestisierung) of fields by the function of the electronic switch 3 with turned off.

When the field windings are excited, the electronic switch is 3 blocked. There is an armature freewheeling current from the motor smoothing throttle 7 via the parallel-connected branches field winding 17 / field series resistor 14 or Field winding 19 / field series resistor 15, the armature freewheeling diode 13, the switch F8 and F2 the two armature windings 5, 11 connected in parallel with the corresponding Series diodes 6, 9 and switch F3 back to choke 7.

The current for charging the field windings leads through the field resistors 14, 15, but the resulting losses are negligible during driving.

The concept of the braking circuit with controlled field weakening is building on a circuit in which the motor fields of the series motors are not direct in the armature circuit, but parallel to the motor armature and the braking resistor 22 and the energy source (catenary network). The braking force is controlled by the DC choppers in series with the motor fields controlled by the field currents, without the need for a grading of resistance. The motor fields have their own freewheel circuits i se.

The explanation of the processes in the circuit begins with a braking process from high speed and monitored motor field (modulation of the DC converter goes towards 0).

If the electronic switch 3 is switched through, the armature current is divided in one part each through the load circuit (Braking resistor 22 or contact line network) and through the motor fields. The inductance of the motor fields 1Rt only a slow one Current build-up too. The current-carrying duration of the electronic switch 3 determines the Field currents. As soon as the armature current flows undivided into the load circuit again, the field currents close via the composite brake resistor 26 and the field freewheeling diode 16 or the control thyristors 18, 20. The field circuits are only taken from the armature circuit the energy to cover their losses. The electronic switch 3 only controls the level of the field currents, but has only an insignificant effect on the flow of energy to the load circuit Influence.

The conditions change with decreasing speed, because the increase the decreased armature voltage to the voltage of the load circuit above it (energy source) requires an increasingly longer switching time of the electronic switch 3. The field currents finally take - as with the series motor circuit - the Value of the armature current. The armature circuit is in turn only the energy to Cover for losses taken in the field circles.

There is a transition zone between the two areas mentioned, in which the field control of the transformation of the armature voltage more and more is replaced. The characteristics in this transition zone can be determined by the size of the composite brake resistor 26.

The composite braking resistor 26 determines the field time constant, what has a particularly favorable effect on the control dynamics of the circuit. Furthermore the resistor 26 increases the stability of the braking circuit.

The braking resistor 22 is set according to the recording capability of the contact line network switched on via the brake thyristor 21. Through periodic Cancellation of the braking thyristor 21 via the electronic switch 3 and by changing it its switch-on time, the current through the braking resistor 21 can increase steadily continuously adapted to changing load conditions of the catenary network. The duration of this resistor is inversely proportional to the absorption capacity of the catenary network.

The line protection resistor 24 has protective functions for the motors at Mains short circuit and serves as a series resistor for operating cases in which the motor voltage is above the maximum permissible mains voltage. In pure line braking mode, the resistor 24 only has the mains current flowing through it. In the high speed range with large Braking power, it helps to keep extreme power peaks away from the network.

In detail, the brake switches B1, B4, Bs, B6 are in the braking mode closed, all other switches are open. When the electronic Switch 3 results in a current flow from the parallel branches on the winding 5 / series diode 9 or armature winding 11 / series diode 6 via switch Bs, the smoothing choke 7, the composite brake resistor 26, the parallel branches of the field winding 17 / field series resistor 14 or field winding 19 / field series resistor 15, the armature freewheeling diode 13, the switch B1, the electronic switch 3 and the switch B4 back to the two armature branches.

At the same time, the armature current also flows from the Brerns composite resistor 26 via the line protection resistor 24, the regenerative diode 23, the choke 2 and the Positive pole 1 back to the energy source, the circuit being over the Motor smoothing throttle 7, switch B6 and components B4 - 5/9 or 11/6 - Bs - 7 closes.

When switch 3 is blocked, armature current flows from the negative pole 8 of the energy source via switches B6, B4, winding the parallel armature branches 5 / diode 9 resp.

Winding 11 / diode 6, the switch Bs, the choke 7, the composite braking resistor 26, the network protection resistor 24, the regenerative diode 23 and the choke 2 to the positive pole 2 of the energy source.

At the same time, there is a freewheeling field current from the field windings 17 and 19 via the respective downstream field resistors 14 and 15, the field freewheeling diode 16 and resistor 26.

This field freewheeling current is only available when the thyristors are blocked 18, 20 valid. However, it is also intended for the braking operation, the armature currents of both motors 4, 10 and an ignition of the control thyristors 18, 20 in Dependence of the measured armature currents to make the armature currents for equality to regulate. The stability of the circuit is especially important with a large actuator modulation improved by the field resistors 14, 15.

Switches B1, B4 and are also in resistance braking mode Bs closed, all other switches are open. When the electronic Switch 3 and ignited brake thyristor 21 results in an armature current flow from the switch B4 via the parallel armature branches winding 5 / diode 9 or winding 11 / diode 6, the Switch Bs, the choke 7, the composite braking resistor 26, the mains protection resistor 24, the braking resistor 22 and the braking thyristor 21 back to the switch Bw.

At the same time, a field freewheeling current flows from the field winding 17 Via the field series resistor 14, the field freewheeling diode 16 and the resistor 26 back to the winding 17 or from the field winding 19 via the field resistor 15, the diode 16 and the resistor 26 back to the winding 19. With blown control thyristors 18 and 20 result in corresponding freewheeling field currents from the windings 17 and 19 via the thyristors 18 or 20 and the resistor 26.

When the electronic switch 3 is activated, there is a flow of current through the parallel field branches field winding 17 / series resistor 14 or field winding 19 / series resistor 15, the armature freewheeling diode 13, the switch B1, the electronic Switch 3, switch Ba, the parallel armature branches winding 5 / diode 9 or

Winding 11 / diode 6, switch B5, motor smoothing choke 7 and resistor 26 back to field windings 17, 19.

Brake switch B6 is also closed in resistance braking mode, but without current. The braking resistor 22 is dimensioned such that the on him the falling voltage is less than the voltage at the input filter capacitor 12. As a result, the feedback diode 23 is not conductive and there is no current flow the feedback diode 23, the input filter choke 2, the positive pole 1, the negative pole 8 and the brake switch B6.

The transition from mains to dynamic braking operation is only possible through Ignition of the braking thyristor 21 accomplished.

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Claims (4)

Claims 0 DC chopper circuit for one through DC series motors Drivable electric vehicle with automatic field weakening when driving and controlled field weakening in braking operation, characterized in that when used of two or more parallel connected DC series motors (4,10) the Field winding (17, 19) with each motor via its own field resistor (14, 15) a common field freewheeling diode (16) and directly with one of these freewheeling diodes bridging control thyristor (18, 20) is connected. 2. DC chopper circuit according to claim 1, characterized by an activation of the regulating thyristors (18, 20) during the period of free-running of the field currents depending on the difference in armature currents. 3. DC chopper circuit according to claim 2, characterized by the use of a three-point controller. 4. DC chopper circuit according to one of the preceding claims, characterized in that each direct current series motor (4, 10) for decoupling a series diode (6,9) is in series.