AU2772400A - Controller of electric rolling stock - Google Patents

Description

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION NAME OF APPLICANT(S): Iitachi, Ltd.

.s ADDRESS FOR SERVICE: DAVIES COLLISON CAVE Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

INVENTION TITLE: Controller of electric rolling stock The following statement is a full description of this invention, including the best method of performing it known to me/us:- I a BACKGROUND OF THE INVENTION TECHNICAL FIELD OF THE INVENTION The present invention relates to a controller of electric rolling stock and, more particularly, to a controller for controlling an electric motor driving an electric rolling stock, by an inverter without using any 10 speed sensor of the electric motor.

DESCRIPTION OF PRIOR ARTS Hitherto, in control of an induction motor by an inverter, vector control systems are used for control which 15 requires a control response. The vector control systems •eg.

each control independently an exciting current component and torque current component of motor current. Of the vector control systems, a slip frequency type vector control system is used in general, which controls output frequency of an inverter on the basis of what slip frequency according to load torque of the electric motor is added to a rotational speed detection value of the electric motor. However, since provision of a speed sensor on the electric motor has such problems that wiring from the speed sensor to a controller of the inverter is necessary, that a cost rises thereby, that a time required for maintenance of the sensor can not be ignored, etc, a control system without use of any speed sensor is proposed. An example of the control system is disclosed in JP A 9-140200. In the example, a rotational speed is estimated on the basis of a sensed exciting current component, a torque current component, a voltage command signal and a motor constant of an electric motor to be controlled.

Further, an example of a control system proposed for electric rolling stock is disclosed in JP A 8-80082. The control system outputs a command of a time varying rate of 10 frequency by a current controller so that a difference between a detection value and a command value of output current of an inverter becomes small, and produces an inverter output frequency command by time-integration of the output. However, it is made so that a detection value 15 from a speed sensor mounted on the electric motor is set as an initial value of its output frequency at the time of start-up of the inverter. Further, in electric rolling stock for railway, iron wheels are adhesively driven on iron rails, so that there are specific phenomena that driving wheels slip or slide. In order to effect readhesion control to suppress the slipping and sliding, a speed sensor is provided on an electric motor.

The control system disclosed in the above-mentioned JP A 9-140200 does not use a speed sensor for inverter control, however, it also is necessary to consider variation in constant because calculation for estimating a rotational speed of the electric motor is complicated and 3 the motor constant of the driving electric motor is used for the calculation.

Further, in the control system disclosed in JP A 8- 80082, an output of a speed sensor is in initializing of an integrator and in re-adhesion control, therefore, the system is not made completely speed-sensorless.

SUMMARY OF THE INVENTION :An object of the present invention is to provide a 10 controller of electric rolling stock, which is completely unnecessary to provide any speed sensor or tachometer mounted on an electric motor for driving the electric .o rolling stock, and can effect acceleration deceleration control of the electric motor and re-adhesion control necessary for the electric rolling stock by an inverter, by estimating a rotational speed of the electric motor with a simple construction.

The above object is achieved by a controller of electric rolling stock which comprises an electric motor driving an electric rolling stock, an inverter outputting AC of variable voltage and variable frequency to the electric motor, speed estimating means for estimating rotational speed of the electric motor and control means for controlling the inverter on the basis of estimation values of rotational speed from the speed estimating means, and which is characterized in that the electric rolling stock is provided with at least one of an automatic train 4 control device for automatically controlling the electric rolling stock on the basis of electric rolling stock speed signals, a tachometer detecting rotational speed of a nondriven wheel of the electric rolling stock and an accelerometer detecting acceleration of the electric rolling stock, and that the speed estimating means has a means for estimating a rotational speed of the electric motor on the basis of the electric rolling stock speed signals or detection signals obtained therefrom.

:00. 10 Further, the object is achieved by that when the inverter is restarted to effect power running or regenerative operation from a coasting operation for stopping the inverter, there are provided means for memorizing estimation values of rotational speed in the 15 speed estimating means at the time the electric rolling stock entered the coasting operation and means for setting estimation values of electric motor speed at the time of S"restart-up of the inverter on the basis of the memorized estimation values of rotational speed.

Further, as for the re-adhesion control, it can be achieved by means for calculating a time change quantity of estimation value of rotational speed of the electric motor, estimated by the speed estimating means and changing according to time passage, means for decreasing the torque component command value according to the time change quantity or decreasing the torque component command value by a pattern of prescribed time function.

BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a block diagram of a basic construction of an embodiment of the present invention; Fig. 2 is a view of a construction of a speed estimation unit 8 of the present invention; Fig. 3 is a view of another construction of the speed estimation unit 8 of the present invention; Fig. 4 is a view of another construction of the speed estimation unit 8 of the present invention; 10 Figs. 5(b) and 5(c) each are a graph of simulation results at time of re-start of an inverter according to the present invention; Fig. 6 is a construction view of a re-adhesion ooe, controller 10 of the present invention; and 15 Figs. 7(b) and 7(c) each are a graph of eoe.

simulation results at time of occurrence of slip according S. to the present invention.

o• DESCRIPTION OF EMBODIMENTS OF THE INVENTION Hereunder, a basic construction of an embodiment of the present invention will be explained, referring to Fig. i.

The construction of Fig. 1 is shown by a block diagram of a controller which controls to drive an electric rolling stock running on a railway. Although not shown in Fig. i, an usual associated train has a plurality of electric rolling stocks connected with each other, and commands corresponding to operation/stopping commands and a torque 6 command are transmitted to the controller of each electric rolling stock from a cab of a head rolling stock of the electric rolling stock by LAN, etc, mounted on the electric rolling stock.

In Fig. 1, a reference number 1 denotes an inverter of pulse width modulation (hereunder, referred to as PWM) inverting DC into AC (including its reverse converting function) by using a plurality of switching elements, and a filter condenser 12 for flattening DC supplied from a DC 10 power source 11 is connected to a DC side of the inverter 1. On an AC side of the inverter 1, a three-phase induction motor 2 (hereunder, referred to as a motor) rotating drive wheels of the electric rolling stock is connected. Further, only one motor is connected on the AC 15 side of the inverter for convenience of explanation in Fig.

1i, however, in many cases, the electric rolling stock has 2 or 4 motors connected thereto.

A reference number 3 denotes a current command generator which generates an exciting current command value Id* and a torque current original command value Iq*. 4 denotes a subtracter, which subtracts an output A Iq* of a re-adhesion controller 10 from the torque original command value Iq* and outputs a torque current command value Iq*.

denotes a coordinates converter, which inputs current iu, iv, iw detected by current detectors 14u, 14v, 14w detecting AC output current of the PWM inverter 1, and converts it into an exciting current component detection 7 value Id and a torque current component detection value Iq.

7 denotes a subtracter, which subtracts the torque current component detection value Iq from the torque current command value Iq** to output a difference AIq of torque current. 8 denotes a speed estimation unit, which outputs an estimation value of rotational speed of the motor 2 from the torque current difference iIq and an electric rolling stock speed signal Vt which is an output of an electric rolling stock speed detector 13. The above-mentioned re- 10 adhesion controller 10 detects slip and slide of the wheels driven by the motor 2 by the estimation value Fr of rotational speed and outputs a signal AIq* to make small the magnitude of a torque current command value when the o slip and slide is detected. 6 denotes a vector control 15 arithmetic unit, which calculates and outputs voltage command values Vd*, Vq* given the induction motor, from the exciting current command value Id*, torque current command value Iq and estimation value Fr of rotational speed.

Further, the detailed calculation is disclosed in the above-mentioned JP A 9-140200, so that it is omitted here.

9 denotes a PWM signal arithmetic unit, which produces PWM signals Su, Sv, Sw of on-off pulses from voltage command values Vd*, Vq* and outputs them to the inverter 1.

Further, in Fig. 1, as for the construction of the present invention, each control function is expressed by a block diagram for convenient of explanation, however, at least blocks 4-8 and 10 can be simply achieved by software processing, using a microcomputer.

Next, in the above construction, features of the present invention reside in the speed estimation unit 8 estimating rotational speed of the induction motor and the re-adhesion controller 10 detecting slip and slide and effecting re-adhesion control.

Details of embodiments thereof will be described hereunder.

10 Fig. 2 shows an embodiment of a construction of the ooo.

speed estimation unit 8 of the present invention. 81 denotes a current controller which, for example, effects proportional integral control expressed by the following equation, and outputs such an output /AFr that the torque :i 15 current difference AIq becomes small (approaches to 0).

Here, K, and K 2 are a proportional factor and an integral factor, respectively, and s is a Laplace operator.

AFr (K i K2/S) AIq 82 denotes a coefficient multiplier, which is for multiplying a coefficient used for converting a speed signal Vt of the electric rolling stock itself into a rotational speed of the motor. 83 denotes an adder, which adds an output AFr of the current controller 81 and an output of the coefficient multiplier 82 and outputs a rotational speed estimation value Fr of the motor.

With this construction, a speed of the motor can be attained by obtaining a rotational speed estimate Fr of the motor without provision of any rotational speed sensor on the motor. Here, a speed signal of the electric rolling stock is a speed signal from a speed detector installed for usual operation of the electric rolling stock, such as an automatic train stopping device (ATS), automatic train controller (ATC), etc, or a speed signal of an automatic train operation device (ATO) (in the specification, an automatic train controller is given as a general name to the ATS, ATC and ATO, and Vt is a speed signal used do do 10 therefor). In another way, it is possible to use, as an d electric rolling stock speed signal, an output signal from a speed detector attached to a wheel shaft of a non-driven wheel for actuating the speed meter, or a value obtained by integrating a value of an acceleration sensor provided for 15 measuring acceleration of the electric rolling stock in the eo. backward and forward direction thereof. In this case, unlike a speed sensor, the acceleration sensor can be provided at any place of the rolling stock body, so that wiring to the controller is unnecessary because of provision of the acceleration sensor inside the controller and the cost can be reduced thereby.

Further, a speed signal Vt of the electric rolling stock is sufficient even if the precision thereof is a little low or there is a delay in detection, as shown by simulation results which will be described later. In this case, an error in the speed signal Vt to a real electric rolling stock speed is corrected by an output AFr of a current controller 81.

That is, the reason that an estimate Fr of rotational speed of the motor which is an output of the current controller 81 is corrected with the speed signal Vt of the electric rolling stock, is: reducing the instability in control done using an estimate Fr of rotational speed of the motor, estimated only by an output of the current controller 81 and reducing the instability of an *e.i estimate Fr of rotational speed of the motor, estimated by 10 an output of the current controller in the case where the electric rolling stock is brought into power running or regenerative operation by re-starting the inverter from an coasting operation to stop the inverter during operation of eoo the electric rolling stock.

:i 15 Fig. 3 shows another embodiment of construction of the oo o speed estimation unit 8 of the present invention. A point different from the embodiment of Fig. 2 resides in setting an initial value of an integrator 812 in the current controller 81 which is composed of a ratio resistor 811 and the integrator 812. 84 denotes an initial value setter, which has a function of converting a speed signal Vt of the electric rolling stock into a rotational speed of the motor and setting the value thus converted as an initial value of the integrator of the current controller 81. The setting is sufficient if 0 is inputted as an initial value of the integrator when the electric rolling stock is at a stop, however, in the case where the inverter is re-started after the operation of the inverter is once stopped during running of the electric rolling stock (coasting operation), it is necessary to input, as an initial value of the integrator, a motor rotational speed corresponding to the electric rolling stock speed at that time, and the initial value is set by the initial value setter 84. A speed signal Vt of the electric rolling stock, which is set as an initial value, is found not to greatly affect the control *999 o :~even if it is slightly low in precision and delayed in 10 detection, as shown by the simulation result which will be described later.

Fig. 4 shows another embodiment of construction of the speed estimation unit 8 of the present invention. A point different from Fig. 2 and Fig. 3 is in that a speed signal 15 Vt of the electric rolling stock is not used for estimation 9*9* oo. of rotational speed of the motor. The electric rolling stock is provided with an operation command generator not shown, and operation/stopping commands such as operation command of power running and regenerative operation and stopping (coasting) are outputted therefrom to the inverter controller of the electric rolling stock. In the embodiment of Fig. 4, the initial value setter 84 and a holder 85 are operated in response to the operation/stopping commands. In the case where the electric rolling stock starts its operation from the time of stopping, the integrator 812 is set 0 as an initial set value thereof by the initial value setter 84. Next, when a stopping (coasting) command is issued at the time the electric rolling stock having been started reaches a prescribed speed, the operation of the inverter is stopped and the holder 85 holds a value of speed estimate Fr at the time of stopping. Further, here, it is possible to hold an output of the integrator 812 instead of a value of the speed estimate Fr. In an initial value arithmetic unit 86, until the inverter restarts, a rotational speed of the see motor in the period of coasting is calculated to estimate, 10 considering the held speed estimate Fr, for example, with rolling friction, air resistance and coasting time during coasting, and the result is outputted to the initial value oo setter 84. Further, the initial value arithmetic unit 86 is not always necessary for achieving the present 15 invention, and if it is unnecessary, it is possible to directly output the held value Fr as it is to the initial :value setter 84. The initial value setter 84 gives a value oo o •outputted from the initial value arithmetic value 86 as an initial value of the integrator 812 of the current controller 81 in the case where the inverter restarts from the stopping condition of the inverter.

As above, the three embodiments of the speed estimation device are explained, and acceleration deceleration characteristics of the inverter are confirmed by the following simulation when the speed estimation unit of the embodiment of Fig. 3 of the above-mentioned three embodiments is used in the controller in Fig. 1.

Figs. 5(b) and 5(c) show simulation results about inverter acceleration characteristics in the case where the inverter is restarted from a coasting operation, which operation condition is considered to be most sever in evaluation. Fig. 5 shows a command value Id* of exciting current value to time t and its detection value Id, and a command value Iq* of torque current component and its detection value Iq, Fig. 5 shows motor torque to time t and Fig. 5 shows real 10 rotational speed (real Fr) and estimate (Fr) of the motor to time t Upon the simulation, the condition that e• setting is effected is as follows. The case where an gee• initial value of the integrator 812, set when the operation :i enters a re-start phase from the coasting operation has an error to a real rotational value is set, the real rotational speed is given 18 Hz as an initial value at o*eoe Hz, an exciting current command Id* is raised at t=0 and then a torque current command Iq* is raised at t 0.8 s.

In the same Figure, when the exciting current starts to rise, the estimate Fr promptly converges the real rotational speed (real Fr) by an operation of the speed estimation unit 8 and then is kept in accord therewith.

Further, in this manner, it is found that an estimate Fr accords with a real rotational speed by operation of the current controller even if there is a slight error in initial value. Further, when a torque current command is raised, torque is established according thereto, and 14 acceleration control can be carried out without any trouble, without use of real rotational speed of the motor.

Further, although not shown in Figure, it is confirmed that when an error is too large in setting of an initial value, s acceleration can not be effected and it converges a value different from a real rotational speed. It is found that how to give an initial value according to the present invention has important meaning.

From the above, in the control construction of the o..

10 electric rolling stock, according to the embodiment in which any one of the embodiments of Fig. 2 to Fig.. 4 is used for the speed estimation unit 8, in the case where the 00oo inverter is once stopped during running of the electric rolling stock and then restarted, an effect that it is unnecessary to use a detection value of rotational speed of e. the motor can be obtained.

Further, in the simulation, gain K 1

K

2 of the current controller 81 are fixed, however, it also is confirmed that the gain of the current controller 81 is made larger than in a usual operation condition (raised in a response speed of the controller) when a speed estimate is obtained by using an initial value at time of start or restart of the inverter, whereby a time required for causing the initial value of a speed estimate to accord with the real speed when there is an error therebetween can be shortened.

Thereby, it is possible to attain an effect that prompt and stable control can be effected.

Next, a detailed construction of the re-adhesion controller 10 of Fig. 1 in which output of a rotational tachometer is not used, according to the present invention will be explained. First, a principle of the present invention is explained, supposing a case of slip. As for slide, the principle is the same as the slip except only that its operation is reverse to the slip, so that its :..:explanation is omitted here. In Fig. i, when slip occurs to the wheel (not shown) driven by the motor 2, the 10 rotational speed rapidly becomes large, slide frequency imparted to the motor decreases. At this time, motor current, that is, torque current Iq decreases, and torque current deviation AIq which is an output of the subtracter 7 becomes large. As a result, the current controller 81 of the speed estimation unit 8 operates and a rotational speed estimate Fr of the motor becomes large. That is, when slip ooeo•: "occurs and rotational speed of the motor becomes large, the rotational speed estimate Fr also becomes large, so that occurrence of slip can be detected by observation of change in rotational speed estimate Fr. Without doing anything as it is, the slip diverges, therefore, the re-adhesion controller 10 controls the torque current command Iq* so as to becomes small, by detecting the slip from change in rotational speed estimate Fr, thereby to suppress the slip and make re-adhesion.

Fig. 6 shows an embodiment of a construction of the readhesion controller 10 based on the above-mentioned principle of the present invention. 101 denotes a differentiater, which calculates a time varying quantity of a rotational speed estimate Fr. 102 denotes a slip detector, which judges that slip occurs when an output from the differentiater 101 exceeds a prescribed value and outputs a slip ON signal In the case where once the slip becomes ON and then an output from the differentiater 101 decreases to be less than the prescribed value, the slip detector judges that the slip has terminated and outputs a slip OFF signal 103 denote a pattern generator, which outputs quantities increasing at a o* prescribed rate when a slip ON signal is inputted, outputs quantities decreasing at a prescribed rate until it becomes 0 when a slip OFF signal is inputted, and holds 0 when it becomes 0.

Even if slip occurs, the slip is detected and an output Iq* which makes a torque current command Iq** small is given by operation of the re-adhesion controller 10, so that the motor torque becomes small, the slip is suppressed and re-adhesion is achieved. When the re-adhesion occurs, the output AIq* is gradually restored, whereby necessary torque is secured. Further, in the construction example, the torque current command is reduced by an output of a prescribed pattern of the pattern generator 103, however, instead thereof, the torque current can be reduced according to a time varying quantity of a rotational speed estimate Fr.

17 Figs. 7(b) and 7(c) show results of simulation for confirmation of an operation for slip phenomena when the construction embodiment of Fig. 6 is applied into the controller of Fig. 1. In Fig. 1, characteristics (b) and are the same as in Fig. 5. In this simulation, when the motor torque exceeds a prescribed value, it is assumed that adhesive force between the rail and the wheel decreases and slip occurs.

As shown in Figs. 7 7(b) and when slip o..

occurs, the torque current is reduced, and it is found that in the re-adhesion controller 10, the slip is detected from •c a time varying rate of rotational speed estimate Fr having ee•• exceeded a prescribed value, and an operation of reducing the torque current is effected. Further, after that operation, the torque current component is restored, so S: that it is found that re-adhesion control is effected. In S"this simulation, slip repeatedly occurs 5 times during acceleration, however, it is found that the motor speed due to the slip does not diverge in any time and re-adhesion control is effected.

In this manner, according to the construction of the present invention, the effect can be attained that slip is detected by change in a speed estimate when the slip occurs and re-adhesion control is effected, whereby the control can be effected without detection of rotational speed of the motor.

In the above embodiments, it is explained that the induction motor is driven by the vector-controlled inverter, however, the present invention is not limited thereto, but can be applied to a speed-sensorless construction in which an output of the current controller controlling an instantaneous value of output current of the inverter is used as an estimated value of rotational speed of the motor.

Further, the embodiments of the present invention is e explained about a controller for an electric rolling stock o 10 running on an rail way, however, the present invention is not limited thereto, and it is a matter of course that the same effect can be attained even if the present invention is applied for a controller for an electric vehicle running on a road, for example.

According to the present invention, basically without directly detecting rotational speed of the motor, variable speed control of the motor can be effected by the inverter, using an estimated motor rotational speed. Particularly, even in the case where an operation of the inverter is stopped under the condition that the electric rolling stock is running and then re-started, the rotational speed can be estimated with a simple construction and smooth acceleration deceleration control is possible. Further, even in the case where the motor slips and slides, readhesion can be effected by adjusting the current command on the basis of an estimated rotational speed of the motor.

At this time, re-adhesion control does not depend on a real 19 rotational speed of the motor, so that erroneous detection of slip and slide due to external disturbance of a speed sensor, etc. is eliminated and adhesion performance can be improved.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

S

e e *DO

Claims (7)

1. 2. A controller of electric rolling stock comprising an electric motor driving an electric rolling stock; an inverter outputting AC of variable voltage and variable frequency to said electric motor; 21 speed estimating means for estimating rotational speed of said electric motor; and control means for controlling said inverter on the basis of an estimation value of rotational speed from said speed estimating means, wherein when said inverter is restarted to effect power running or regenerative operation from a coasting operation for stopping said inverter, and there are provided means for memorizing estimation values of rotational speed in said speed estimating means at the time said electric rolling stock entered the coasting operation and means for setting oo an estimation value of electric motor speed at the time of restart-up of said inverter on the basis of the memorized estimation value of rotational speed.
2. 3. A controller of electric rolling stock comprising 000000 an electric motor driving an electric rolling stock; an inverter outputting AC of variable voltage and variable frequency to said electric motor; speed estimating means for estimating rotational speed of said electric motor; control means for controlling said inverter on the basis of an estimation value of rotational speed from said speed estimating means; and at least one of an automatic train control device for automatically controlling said electric rolling stock on the basis of electric rolling stock speed signals, a 22 tachometer detecting a rotational speed of a non-driven wheel of said electric rolling stock and an acceleration sensor detecting acceleration of said electric rolling stock, wherein said speed estimating means comprises a means for inputting a difference between a detected current value of said inverter and a current command value thereof at least into an integrator and outputting an estimation value of said rotational speed so that the difference becomes small, *ee. 10 and means for correcting the estimation value by at least a signal of electric rolling stock speed signal of said automatic train control device and a detection signal from said tachometer and accelerometer. e*e.
3. 4. A controller of electric rolling stock comprising an electric motor driving an electric rolling stock; ooo* an inverter outputting AC of variable voltage and variable frequency to said electric motor; speed estimating means for estimating rotational speed of said electric motor; control means for controlling said inverter on the basis of estimation values of rotational speed from said speed estimating means; and at least one of an automatic train control device for automatically controlling said electric rolling stock on the basis of electric rolling stock speed signals, a tachometer detecting rotational speed of a non-driven wheel 23 of said electric rolling stock and an acceleration sensor detecting acceleration of said electric rolling stock, wherein said speed estimating means comprises a means for inputting a difference between a detected current value of said inverter and a current command value thereof at least into an integrator and outputting an estimation value of said rotational speed so that the difference becomes small, S"means for calculating an estimation value of rotational 0 speed corresponding to the rotational speed of said electric motor by at least one of an electric rolling stock speed signal of said automatic train control device and eoee eeoc detection signal from said tachometer and said acceleration sensor, and means for initializing an estimation value of 15 said speed estimating means by the estimation value of rotational speed. o A controller of electric rolling stock comprising an electric motor driving an electric rolling stock; an inverter outputting AC of variable voltage and variable frequency to said electric motor; speed estimating means for estimating rotational speed of said electric motor; and control means for controlling said inverter on the basis of estimation values of rotational speed from said speed estimating means, wherein said speed estimating means comprises a means for -p 24 inputting a difference between a detected current value of said inverter and a current command value thereof at least into an integrator and outputting an estimation value of said rotational speed so that the difference becomes small, means for memorizing estimation values of rotational speed in said speed estimating means at the time said electric rolling stock entered the coasting operation when said :i inverter is restarted to effect power running or regenerative operation from a coasting operation for 10 stopping said inverter, and means for initially setting e estimation values of electric motor speed at the time of restart-up of said inverter on the basis of the memorized *oo estimation values of rotational speed. 15 6. A controller of electric rolling stock according to claim 5, wherein an initial value of the estimation value of rotational speed of said electric motor at the time of restart-up is set on the basis of at least the stored estimation value of rotational speed and a coasting time of said electric rolling stock.
4. 7. A controller of electric rolling stock comprising an electric motor driving an electric rolling stock; an inverter outputting AC of variable voltage and variable frequency to said electric motor; speed estimating means for estimating rotational speed of said electric motor; and control means for controlling said inverter on the basis of estimation values of rotational speed from said speed estimating means, wherein said speed estimating means comprises a speed estimating means for inputting a difference between a detected current value of said inverter and a current command value thereof at least into an integrator and outputting an estimation value of rotational speed of said electric motor so that the difference becomes small, and 10 means for making response speed of said speed estimation means variable and raising the response speed at the time of start-up or restart of said inverter. ••co
5. 8. A controller of electric rolling stock according to any one of claims 3 to 7, wherein a detection value of inverter output current in said speed estimating means and its command value are a detection value corresponding to a torque component of said electric motor and its command value, respectively.
6. 9. A controller of electric rolling stock according to claim 8, wherein there are provided means for calculating quantities changing according to time, of estimation values of rotational speed of said electric motor, estimated by said speed estimating means, and means for decreasing the torque component command value according to the quantities changing as time changes or according to patterns of 1W 26 prescribed time function, in response to that the quantities changing as time changes exceeds a prescribed value. ge.. S S. .SSS *4 S S *S S 5**S *555 55*5 S. 9 S S S S 0 27 A controller of electric rolling stock substantially as hereinbefore described with reference to the drawings and/or Examples.
7. 11. The steps, features, compositions and compounds disclosed herein or referred to or indicated in the specification and/or claims of this application, individually or collectively, and any and all combinations of any two or more of said steps or features. o so o* eo. DATED this TWELFTH day of APRIL 2000 4 Hitachi, Ltd. S". by DAVIES COLLISON CAVE Patent Attorneys for the applicant(s)