RU2359400C2 - Frequency-controlled asynchronous electric drive - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: present invention relates to electrical engineering and can be used in rail vehicles and directly relates to asynchronous traction drives of railway engines. The frequency-controlled asynchronous electric drive for rail vehicles contains an electric motor at least two arc stator windings, mechanically linked to the wheel pair, fitted on the rails, a speed sensor for the electric motor and a control system. The control system consists of a static frequency converter with self-excited inverters for powering the stator windings and a unit for controlling the converter with feedback on speed and direct contact with the static frequency converter. The control system generates signals for controlling the inverters using an algorithm with single commutation of bearing elements in one period. It also provides for changing frequency of voltage at the outputs of the self-excited inverters and shifting current of the inverters relative each other by an angle, defined by the number of arc windings. The electric drive is provided with a device for measuring rotational acceleration of the electric motor, connected to the speed sensor of the electric motor and detecting onset and end of the process of slippage of the wheel pairs, and a device for regulating angle of displacement of current of arc stator windings. When the wheel pair is slipping, the regulator provides for reduction of the angle of displacement of supply current of arc windings in the range π/3k>Θ≥0, defined by the number of arc stator windings, from signals coming from the device for measuring acceleration. The required pulsation of rail tractive force of the drive is set, which allows for attaining maximum tractive force with useful sliding motion in the zone of maximum possible traction coefficient.

EFFECT: improved towing performance of the electric drive in conditions of limited interlocking of wheel pairs and rails.

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Description

The invention relates to rail vehicles and directly relates to asynchronous traction drives of locomotives.

Known frequency-controlled asynchronous electric drive [Pat. 2194355 RF. Frequency-controlled asynchronous electric drive / M.V. Zagorsky, V.I. Vorobyov, A.I. Ivakhin, G.S. Mikhalchenko], containing an electric motor that is equipped with at least two arc stator windings and is mechanically connected to the wheel pair, mounted on rails, as well as an electric motor speed sensor and a control system consisting of a static frequency converter with autonomous inverters, each of which is connected to a separate arc stator winding, and a converter control unit with feedback on the sensor in speed and a direct link with a static frequency converter. In this case, the currents of the autonomous inverters are shifted relative to each other by an angle determined by the number of stator arc windings.

The disadvantages of the indicated technical solution include the unregulated angle of bias of the supply currents of the stator arc windings, which does not allow controlling the tangential force of the drive traction when the process of boxing of the wheel pair occurs.

The technical result of the invention is to improve the traction properties of the drive in conditions of limited adhesion of the wheelset and rails by adjusting the angle of bias of the supply currents of the stator arc windings.

The technical result is achieved by the fact that the electric drive contains an electric motor that is equipped with at least two arc stator windings and is mechanically connected to a wheel pair mounted on rails, as well as an electric motor speed sensor and a control system consisting of a static frequency converter with autonomous inverters, each of which is connected to a separate arc winding of the stator, and the converter control unit, which has feedback on the speed sensor and a direct connection with the static converter frequency caller. The control system through the control unit of the static frequency converter generates control signals for inverters according to an algorithm with a once switching power elements during a period, provides a change in the frequency of voltages at the outputs of autonomous inverters and a shift of the currents of inverters relative to each other by an angle determined by the number of arc windings. In this case, the control unit of the static frequency converter is equipped with a device for measuring the acceleration of rotation of the electric motor, connected with the speed sensor of the electric motor and fixing the occurrence and termination of the process of boxing of the wheel pair, as well as a regulator of the angle of the bias currents of the arc windings of the stator, which according to the signals received from the device for measuring the acceleration of rotation of the electric motor , provides in the mode of boxing a pair of wheels a decrease in the angle of bias of the supply currents of the arc windings in the range IOM arc number of stator windings.

The essence of the invention is illustrated by the drawing.

The electric drive contains (Fig. 1) an electric motor 1 with arc windings 2 of the stator (as an example, Fig. 1 shows an electric drive with three arc windings) mechanically connected to a pair of wheels 3 mounted on rails 4, as well as a speed sensor 5 of the electric motor 1 and control system, which consists of a static frequency converter 6 with autonomous inverters 7 and a control unit 8 of the converter 6. Moreover, each autonomous inverter 7 is connected to a separate arc winding 2, and the control unit 8 has feedback speed sensor 5 and direct communication with a static frequency converter 6.

In the electric drive, the control unit 8 is equipped with a device for measuring the acceleration of rotation 9 of the electric motor 1, connected with a speed sensor 5, and a regulator of the angle of the bias of the currents 10 of the arc windings 2.

The electric drive operates as follows.

Electric drive regulation is carried out in a frequency manner. The control system by means of the control unit 8 by a static frequency converter 6 generates control signals of the autonomous inverters 7 according to the algorithm with switching power elements once per period and provides a change in the frequency f _{1 of the} voltages at the outputs of the autonomous inverters in accordance with the signal f _p of the speed sensor 5 of the electric motor 1 according to the known law f ₁ = f ₂ + f _p , where

f ₂ is the absolute slip frequency (rotor current frequency). In addition, the control system sets the shift of the inverter currents relative to each other by an angle Θ = π / 3k, determined by the number k of stator arc windings 2, where k≥2.

It is known [Kurbasov A.S., Sedov V.I., Sorin L.N. Design of traction electric motors / Ed. A.S. Kurbasova - M .: Transport, 1987. - p.364-365], that in the low frequency region f _{1 the} supply voltage of the arc windings 2 under the laws of control of a static frequency converter with switching power elements once during a period (λ = 180 e. degrees or λ = 120 e. degrees) ripple δM _α , the torque generated in the motor by each winding can reach 25% or more of its average value (figure 2) depending on a given value of f ₂ and the current value of f _p . In this case, the pulse ripple repetition rate is six times the frequency of the supply voltage, i.e. f _δM = 6f ₁ .

For the angle Θ = π / 3k, the summation of the torques of the arc windings makes it possible to reduce the relative pulsation δM _{Σ of} the motor torque to the minimum possible level while increasing the pulsation repetition rate to f _δM = 6kf ₁ , and also to achieve the required average moment M _{crΣ of the} electric motor ( figure 2 shows the torque of the electric motor with three arc windings). With a decrease in the angle of shear of the supply currents of the arc windings in the range π / 3k> Θ≥0, the ripple δM _{Σ of} the motor torque increases and in the case Θ = 0 reaches a maximum value equal to the ripple δM _{α of the} moment from one arc winding (Fig. 2). In the considered range of angle рассматрива, the frequency of the first harmonic of the pulsation of the motor torque is f _δM = 6f ₁ .

Through mechanical coupling, the engine torque is transmitted to the pair of wheels 3 (FIG. 1) mounted on the rails 4, creating a tangential traction force F _{k of the} drive. As an example, figure 3 shows a simplified traction characteristic of a diesel locomotive [Osipov S.I. and other Fundamentals of locomotive traction / S.I. Osipov., K. A. Mironov, V. I. Revich. - M .: Transport, 1979. -. 440, S.112-121], which represents the dependence tangent locomotive traction force F _{to the} speed of movement V and irrespective of the power limit comprises portions clutch 1 by the starting current limitation traction generator 2 and limits on diesel power 3. The clutch restriction section 1 is calculated for dry rails, and the inrush current restriction section 2 is based on the condition that less traction is realized than on section 1 to reduce the possibility of wheel pair blocking. Starting and accelerating the locomotive is performed according to curve 2, which corresponds to the mode of starting and accelerating the drive at low frequencies f _{1 of the} supply voltage of the arc windings of the engine. The low level of pulsation δM _{Σ of} the engine torque at Θ = π / 3k due to its damping in the mechanical coupling elements (not shown in FIG. 1) practically does not cause pulsation of the traction force F _k .

The wetting of the rails, the ingress of oil into the contact of the wheel and the rail, and other factors cause a decrease in the coefficient of adhesion ψ at all speeds of the locomotive V and, consequently, a decrease in the section 1 of the traction characteristic (in Fig. 3, curve 1 '). As a result, a clutch disruption occurs, leading to a wheel pair boxing mode.

It is known [Minov A.K. Improving the traction properties of electric locomotives and diesel locomotives. - M .: Transport, 1965. - P.229], that the boxing mode starts when the circumferential acceleration of the wheelset w exceeds 0.45-0.5 m / s ² . To highlight the boxing process, the control unit 8 (Fig. 1) with a static frequency converter 6 is equipped with a device for measuring the acceleration of rotation 9 of the electric motor 1, which differentiates the signal according to the rotational speed of the rotor f _{r of the} engine coming from the speed sensor 5:

ε _p = T _d df _p / dt,

where T _d - the time constant of differentiation, the value of which determines the necessary duration of the process of measuring the angular acceleration of the rotor ε _p .

When the signal ε _p is selected, which in terms of the peripheral acceleration of the wheel pair w exceeds 0.5 m / s ² , the device 9 supplies a signal to the angle displacement regulator of the currents 10 of the arc windings 2. The controller 10 provides a decrease in the angle of the current bias of the arc windings 2 in the range π / 3k> Θ≥0 to a value that determines the ripple value δМ _Σ , the engine torque (Fig. 2), at which the boxing process stops. The moment of the end of boxing is also fixed by the device 9 by measuring ε _p corresponding to w <0.45 m / s ² , and a signal is sent from the device 9 to the regulator 10, which sets the angle Θ in the above value. This moment corresponds to point A in figure 3.

The resulting ripple of the engine torque causes a ripple 4 of the thrust force F _k (Fig. 3), which in one part of the ripple period is below the curve 1 ', and in the other part is higher. This allows you to realize the ultimate traction force with useful slippage in the zone of the maximum possible coefficient of adhesion ψ _max under the previously noted adverse operating conditions of the drive. Figure 4 shows the dependence of the friction coefficient ψ on the sliding speed V _ck (or slip coefficient s) 1 at a fixed locomotive speed V [P. Wigner. Traction and energy indicators of electric locomotives of the 250 series // Railways of the world. - 1985. - No. 10, S.9-16]. By a similar dependence, the maximum possible traction force changes, determined by the well-known expression F _к = ψQ, where Q is the coupling weight of the locomotive, and for the drive in question, the axial load. When the ripple is obtained, the traction force F _k is realized along a closed curve 2 (Fig. 4), without leading to a blocking of the wheel pair.

In the event of a repeated occurrence of the process of boxing of the wheelset (Fig. 3, point B), caused by a slight decrease in the value of δM _Σ during the drive acceleration and the discrepancy of the characteristic sections 2 and 1 ', the regulator 10 (Fig. 1) further reduces the angle Θ, and the electric drive works according to the algorithm described above. At point C (Fig. 3), curve 2 or 3 crosses section G of the traction characteristic, which leads to the final cessation of the boxing mode.

The transition of the traction characteristic from section 2 to section 3 usually occurs at locomotive speeds of 5-15 km / h. In section 3, the thrust force F _k decreases rapidly, and the speed V increases. When reaching a speed of V> 15 km / h, guaranteeing an exit from the boxing zone, the control system returns to its initial state by setting the angle of the shift of the inverter currents Θ = π / 3k. This can be done, for example, by switching the controller 10 (Fig. 1) according to the signal f _p of the speed sensor 5, corresponding in terms of the indicated speed. In addition, the return of the system to its original state is likewise carried out according to the signal to turn off the power supply to the drive (load shedding).

The technical and economic efficiency of the invention in comparison with the prototype lies in the fact that in the mode of boxing the wheelset, the electric drive control system reduces the angle of shear of the currents of the arc windings of the electric motor. At the same time, the required pulsation of the tangential force of the traction of the drive is set, which allows you to realize the ultimate traction force with useful slippage in the zone of maximum coefficient of adhesion, due to which the electric drive has increased traction in conditions of limited adhesion of the wheelset and rails.

Claims (1)

A frequency-controlled asynchronous electric drive of a rail vehicle containing an electric motor that is equipped with at least two arc stator windings and is mechanically connected to a wheel pair mounted on rails, as well as an electric motor speed sensor and a control system consisting of a static frequency converter with autonomous inverters, each of which is connected to a separate arc winding of the stator, and the control unit of the converter having feedback on the speed sensor and direct communication with a static frequency converter, while the control system by means of a control unit of a static frequency converter generates inverter control signals according to an algorithm with switching power elements once per period, provides a change in the frequency of voltages at the outputs of autonomous inverters and an offset of the currents of inverters relative to each other by an angle determined by the number arc windings, characterized in that the control unit of the static frequency converter is equipped with a device for measuring acceleration rhenium of rotation of the electric motor, associated with the motor speed sensor and detecting the occurrence and termination of the process of blocking the wheel pair, as well as the regulator of the angle of displacement of the currents of the arc windings of the stator, which according to the signals from the device for measuring the acceleration of rotation of the electric motor, provides a reduction in the angle of shift in the mode of blocking of the wheel pair supply currents of the arc windings in the range π / 3k> Θ≥0, determined by the number k of stator arc windings.

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