DE3010327A1 - DRIVE DRIVE ARRANGEMENT - Google Patents

Description

ASEA AB, Västeras / Sweden Traction drive arrangement

The invention relates to a traction drive arrangement according to the Preamble of claim 1.

So far it has been the case with battery-powered electric vehicles proved necessary to provide special, usually stationary charging units for charging the vehicle batteries. Such Charging units usually contain a transformer and a controllable rectifier as well as control circuits for control the charging history. The nominal power of such a charging unit is relatively high due to the limited charging time, which makes the unit relatively expensive.

The invention is based on the object of a traction drive arrangement to develop the type mentioned, in which the loading arrangement in relation to the known arrangements without a significant increase in the complexity, weight and price of the vehicle is significantly simplified and cheaper can be.

To solve this problem, a traction drive arrangement is proposed, according to the invention in the characterizing part of the

030042/0683

/ 5

January 21, 1980 20 774 P.

Claim 1 has mentioned features.

Advantageous further developments of the invention are set out in the subclaims called.

The invention is to be explained in more detail on the basis of the exemplary embodiments shown in the figures. Show it

1 shows an exemplary embodiment of a traction drive arrangement

according to the invention,
Fig. 2 shows an embodiment of the invention in which the fixed inductors in Fig. 1 on the

Vehicle are arranged,
3 shows an embodiment of the invention in which the transformer for adapting the charging voltage is arranged on the vehicle.

Figure 1 shows a dashed bordered vehicle F, which is a battery-powered electric forklift truck, an electric car ο. like. can be. The drive motor M of the vehicle is a three-phase asynchronous motor and an accumulator battery B. The two DC connections of a three-phase inverter VR are connected to the battery B, while the AC connections of the inverter are connected to the motor M via a switch with two positions SW.

The inverter is self-commutated; so he can do it independently generate a three-phase alternating voltage. The inverter

03Ü042 / 0683/6

January 21, 1980 20 774 P.

Γ ν ¹ /. ''

Is of a known type and consists of a bridge circuit of six thyristors T1 - T6 provided with quenching elements. A diode D1 D6 is antiparallel to each thyristor trained return valve. The inverter has a control pulse element SPD, which sends control pulses to the thyristors and their quenching elements in such a way that a three-phase AC voltage is applied to the output terminals R, S, T of the Inverter receives.

During normal operation of the vehicle, the control pulse member controls the inverter in such a way that the frequency and the amplitude the alternating voltage for controlling the motor can be varied. For example, the control pulse element can be a voltage-controlled one Oscillator included to control the frequency, and the amplitude of the output AC voltage is appropriate, for example by pulse width modulation, controlled so that their amplitude is proportional to the frequency. The way of working and the structure of such an inverter and its control circuits are already known. The changeover switch is in normal operation SW in the fully extended position shown in the figure, and the battery B feeds the motor M via the inverter. By varying the frequency of the inverter, the speed, slip and torque of the motor are influenced. When the frequency of the inverter is lowered so that the slip becomes negative, the motor feeds power into the battery back, which provides electrical regenerative braking. As the control circuits and control elements used in normal operation are already well known, they will be in the

030C42 / GS83 _{/ 7}

January 21, 1980 20 774 P.

Figure not shown in more detail.

To charge the vehicle battery, the switch is placed in its position shown in dashed lines in the figure, whereby the motor of the inverter is switched off and the inverter is connected to the connector Aj in the vehicle. The plug Aj is connected to the fixed socket Ap ₁ to charge the battery.

The AC voltage source for charging the battery consists of a three-phase transformer TR, which is permanently connected to the AC voltage network with the connections Rjj, S ^ and Tjj. The transformer transforms the mains voltage down to a voltage suitable for charging the battery of, for example, 50-100 V. The secondary voltage of the transformer is connected to the socket A _{p1 via the inductances Lj R} >> ₁₃ and L _1T .

The plug Aj, like the socket AF _{1, has} three main sockets (or pins) for connecting the main circuits of the inverter via the switch SW and the inductances L _1R , L _{1 g} and L _1T to the AC voltage source (transformer TR). Furthermore, the plug and socket have three auxiliary sockets or pins for connecting the phase control circuits of the inverter directly to the AC voltage source.

During charging, the inverter is controlled as follows: The inverter generates a rigid alternating voltage at its terminals R, S, T. The secondary voltage of the transformer TR is

030042/0683 / 8

- January 21, 1980

^: . ::. . ν 20 774 P.

also a rigid alternating voltage. These two voltages are connected to _{one another via the inductors L 4 D} , h _{A σ} and Lm.

in. ι ο ix

When the phase difference between the two voltages is small is, as a good approximation, the effective power flow is proportional to the phase difference between the two voltages and that the reactive power flow is proportional to the difference between the amplitudes of the two voltages.

Appropriately, the amplitude of the voltage of the inverter controlled so that it is approximately the same as the amplitude of the secondary voltage of the transformer TR, whereby the reactive power flow between the grid and the inverter is as small as possible. For this purpose the amplitude control input is used AC of the control pulse element SPD of the inverter is supplied with an analog voltage adjustment signal Sy, which is set with the help of a potentiometer P so that the amplitude of the output voltage of the inverter is the desired Assumes value.

To control the phase position of the output voltage of the inverter, the three phase voltages U _R , U _g and Um are _{fed to amplifiers F R} , F _g and F _T , in which the voltages are converted into square-wave alternating voltages U ' _R , U' _s and U ' _{T by amplitude truncation} which are in phase and frequency identical with the voltages U _R , U _g and U _R. These signals are fed to delay elements D _R , Dg and D _T with a controllable time delay. The output voltages S _R , S _g and S_ of the delay elements are fed to the synchronization input S _{c of} the control pulse element

030042/0683 / 9

January 21, 1980 20 774 P.

of the inverter, which controls the output voltages of the inverter for frequency and phase equality with the signals S _R , S _g and S ^.

A known charge controller CR supplies a setpoint I _B0 for the charging current. This target value can be controlled in a known manner as a function of the battery voltage Ug, which is obtained from a voltage divider SD, and as a function of time, so that the charging current has the desired profile. The actual value Ig of the charging current, which is obtained with a measuring shunt SH, is compared with the nominal value in a comparison element JF. The deviation .DELTA.I is fed to a current regulator IR with PI characteristic, the output signal S _{p of} which is fed to the delay elements D _R , Dg, D "and determines the size of the delay.

The phase position of the control signals S _R , S ″, S ″, and thus the EMF of the inverter, is therefore automatically controlled so that the charging current I _ß follows the setpoint I ™ output by the charge controller CR.

The invention has compared to already known traction drive systems significant benefits. The vehicle itself has all of the well-known advantages of an AC powered drive motor, which is cheap and practically maintenance-free Asynchronous motor can act. The control of the motor is smooth, fast and low-loss with the help of the inverter. The vehicle can be braked regeneratively, whereby

/ 10 03Ü0A2 / 0683

January 21, 1980 2 0 774 P.

- 10

there is a significant increase in the distance traveled for a given battery capacity or conversely, a significant reduction in battery size for a given distance is obtained '.

The additional devices required in a vehicle according to the invention consist of the changeover switch SW and the control circuits shown in the figure outside the inverter to the shop. The switch SW can, since it only needs to be actuated in the de-energized state, simple and cheap be. The control circuits can be simple additions to the control arrangement with which the vehicle is already equipped. Neither the switch nor the control circuits therefore cause a significant increase in the vehicle price or weight.

In contrast, a very large simplification of the stationary charging arrangement is obtained. In principle, this only consists of a single transformer. If several vehicles are to be charged at the same time, the transformer only needs to be provided with several sockets. Another such socket Ap ₂ is shown in FIG. It is constructed in exactly the same way as the socket outlet Ap ₁ . The main sockets of this socket are connected via the inductances L _2R , L ₂₃ and L _2T and their auxiliary sockets are connected directly to the secondary side of the transformer TR. The sockets can be arranged at various points in, for example, a factory and connected to a transformer set up at a suitable location. Due to the simultaneity factor, the rated power of the transformer

/ 11 030042/0683

January 21, 1980 20 774 P.

- 11 -

[Γ

be smaller than the sum of the nominal power of the sockets. When an AC voltage of a suitable magnitude to charge the battery is already available, the transformer can be dispensed with, so that the stationary arrangement then only consists of the sockets and the interposed inductances.

The invention thus results in an extraordinary saving compared to already known traction drive systems.

It has been described above how the invention is applied to an electric forklift truck or an electric car. The invention however, it can do just as well with other types of electric vehicles be applied.

A travel drive arrangement according to the invention can consist of one or more vehicles and possibly also the stationary one Include arrangement for charging the vehicle batteries.

In the example described above, the motor fed by the battery via the inverter is a drive motor for the vehicle, but the motor can alternatively also serve as a drive for, for example, the lifting movement of a forklift.

The embodiment of a control arrangement for battery charging described above can be designed in a large number of variants within the scope of the inventive concept disclosed. For example, instead of the simple control of the inverter voltage shown, a closed control loop can be used.

030042/0683 / 12

January 21, 1980 20 774 P.

- 12 -

det that the inverter voltage or the reactive power flow regulates in the desired manner.

Of course, the inverter itself can be replaced by a large number of inverter circuits.

The control of the charging current can differ from the one described Embodiment take place. For example, the charging current can be controlled solely according to a time program Measuring the battery voltage can be omitted.

In the exemplary embodiment described, it is assumed that the vehicle battery is charged from a three-phase AC voltage network. Alternatively, the battery can be charged using a single-phase AC voltage network. The inverter is operated as a single-phase inverter while it is charging, only two of the three phase groups of the inverter being used. The AC terminals, for example R and S, of these two phase groups are then connected to the AC voltage network via a single-phase connection device. An inductance (eg L _1R ) is only required in one of the two phase lines.

FIG. 2 shows a traction drive arrangement which corresponds to that shown in FIG. 1 with the exception that the inductances

^L 1R » ^L 1S ^{f L} 1T are arranged ^{on the fan tool} between the plug A _M and the switch SW. The voltages U _R »Ug, U ™ to the phase

/ 13 030042/0683

January 21, 1980 20 774 P.

-υ-

sensor control of the inverter can then be taken between the inductances and the connector. This significantly simplifies the sockets and plugs, since no auxiliary sockets or auxiliary pins are required to transmit _{the voltages U R} , Ug, U _T. Furthermore, it is not like in Pig. 1, a set of inductors is required at every socket, but only a single set of inductors on the vehicle.

FIG. 3 shows how the transformer TR can be arranged on the vehicle F. The sockets can then be connected to an existing AC voltage network, for example to a normal 380 V three-phase network. The stationary part of the traction drive arrangement then consists only of conventional sockets Ap ₁ , Ap ₂ »Ap ,, which can be arranged simply and cheaply in the desired number and at desired locations in, for example, a factory. Sockets of this type are often already installed in suitable places for charging vehicles. This embodiment results in maximum flexibility with regard to the charging of any number of vehicles at any location, with little or no costs incurred for the stationary part.

The transformer is expediently arranged in the vehicle in such a way that it has a favorable effect on the stability of the vehicle. He can sometimes completely or partially replace counterweights in e.g. a forklift truck, and then it does nothing or only one slight increase in vehicle weight.

/ 14 030042/0683

20 774 P.

■ It was described above how the AC mains voltage (Up »U _a , Um) is sampled and used as a setpoint to control the phase position of the inverter voltage and thus the active power flow (charging current). It is already known to control a converter with the aid of a free-running oscillator with a controllable frequency, which (possibly via auxiliary circuits) sends control pulses to the valves of the converter. If the inverter in the vehicle has or is provided with such an oscillator, then the oscillator can also be used to control the inverter during the charging process. The difference between, for example, the nominal and actual values of the charging current then influences the frequency of the oscillator and thus its phase position, whereby a closed control system is formed which controls the actual value of the charging current to match its nominal value. The scanning of the mains voltage U _R , U _g , U _T shown in Figures 1-3 is then superfluous, whereby the auxiliary sockets and auxiliary sstif te shown in Fig. 1 on the sockets and plugs A ", A ^, Ap" superfluous will.

A vehicle with only one inverter and only one drive motor M has been described above. The invention can can of course also be used in vehicles with several drive motors, for example one for each wheel, either be fed by a common inverter or by individual inverters. The inverter (or a or several of the inverters) can then be used to charge the vehicle battery in the manner described above.

030042/0683 ^{/ 15}

20 774 P - 15 -

A contactor is often required in vehicles of the present type to switch through the supply voltage to the motor. This Contactor can then be designed as a changeover switch and used like the changeover switch SW shown in FIGS. 1-3.

In Figure 3, the transformer is arranged on the vehicle. The transformer can be designed in such a way that its leakage inductance is so great that separate inductances L-jof L ^ g and L «j _T can be dispensed with. The same applies to the embodiments according to FIGS. 1 and 2 if only one stationary socket, for example A _pi , is provided for charging the vehicle.

The embodiments according to FIGS. 1 and 2 can be modified in this way that part of the required inductance is placed in the vehicle and the rest in series with the socket in question will.

0300A2 / 0683

Claims (10)

Patent claims: (1.} traction drive arrangement, which comprises a vehicle with at least one electric alternating current motor and with an accumulator battery for feeding the motor via an inverter, characterized in that the vehicle with members (SW, Α-.) For connecting the alternating current side of the inverter to a stationary alternating voltage source (TR) for charging the battery through the inverter and with control elements (CR, JF, IR, F _R to F "IX. to D _T) for controlling the inverter, and thus the charging current during charging of the battery is provided. 2. Travel drive arrangement according to claim 1, characterized in that the inverter is a self-commutated inverter and that the control members _{contain members (D ^, D g} , D ^,) for controlling the phase position of the inverter voltage relative to the voltage of the AC voltage source (TR). 3. Travel drive arrangement according to claim 2, characterized in that voltage-controlling members (P, SPD) for control the output voltage of the inverter are arranged such that the reactive power flow between the inverter and the AC voltage source is as small as possible while the battery is being charged. / 2 030042/0683 January 21, 1980 20 774 P. 4. Travel drive arrangement according to one of the preceding claims, characterized in that a stationary AC voltage source to it (TR), which is provided with at least one connection element (Ap .., App) for connecting the inverter of a vehicle to charge the vehicle battery. 5. Travel drive arrangement according to claim 4, characterized in that the alternating voltage source consists of a transformer (TR) connected on the primary side to an alternating voltage network, the secondary side of which is connected to the connecting members (Ap ^, Ap ₂ ). 6. Travel drive arrangement according to one of claims 1 to 4, characterized characterized in that it has one on the vehicle (F) between the connector (A ™) and the inverter (VR) arranged transformer (TR) contains. 7. traction drive arrangement according to claim 6, characterized in that the AC voltage source is a normal low-voltage network. 8. Travel drive arrangement according to claim 6 or 7 »characterized in that that the transformer is arranged in the vehicle in such a way that it has an increasing effect on the mechanical stability of the vehicle. 9. Travel drive arrangement according to one of the preceding claims, characterized in that the AC voltage source in Series of inductances connected to each connector 030042/0683 _{/ 3} January 21, 1980 20 774 P. or (L _1R to L _1T , L ₂₁₁ to L _2T ). 10. Travel drive arrangement according to one of claims 1 to 8, characterized in that it contains _{inductances (Imo to L 1T ) arranged on the vehicle (F) between the connecting members (A M} ) and the inverter (VR). 030042/0683 / ⁴