GB2117195A

GB2117195A - Electrical brake system for electric rolling stock

Info

Publication number: GB2117195A
Application number: GB08302143A
Authority: GB
Inventors: Shigeru Koyama; Toshiaki Awano; Susumu Shikata
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1982-03-05
Filing date: 1983-01-26
Publication date: 1983-10-05
Also published as: ES519993A0; GB2117195B; AU1079383A; JPH0437642B2; CA1186037A; JPS58154304A; AU556308B2; GB8302143D0; ES8402210A1

Abstract

An electrical brake system for an electric rolling stock includes a filter condenser (4) and a chopper (7) connected in parallel thereto. If the voltage across the filter condenser (4) rises excessively due to an abrupt variation of the trolly load or a momentary coming-off of the pantagraph 2 from the trolly 1, it is detected and the chopper (7) is operated so as to suppress the excessive voltage and at the same time reduce the chopper current automatically in accordance with a predetermined timing pattern, not to a complete cut off of the regenerative braking current, but maintaining the regenerative control, thereby allowing a quick restoration of the regenerative current when the power system is rid of the disturbance. <IMAGE>

Description

SPECIFICATION Electrical brake system for electric rolling stock The present invention relates to an electrical brake system for an electric rolling stock and, more particularly, to a control system wherein a filter condenser and a control unit are connected in parallel to the DC power supply so that the control unit operates on the driving motor to perform regenerative control and generation control for the vehicle driving motor.

In the conventional regenerative brake control for the electric rolling stock, if the regenerative load on the trolly varies abruptly or the pantagraph comes off the trolly momentarily due to the vibration of the vehicle during a regenerative braking operation, the voltage across the filter condenser rises excessively. On this account, when a voltage rise is detected, the regenerative brake circuit is opened immediately so as to protect the control unit and driving motor.

However, when this method is used for vehicles running on lines with large variation of regenerative load or for street cars whose pantagraph come off the trolly frequently, the regenerative braking operation is interrrupted frequently, resulting in a poor regenerative duty cycle. In addition, an abrupt release of the regenerative braking force and a switching to the additional mechanical braking force with a time lag following the first event create a shock, thereby causing discomfort for the passengers.

A primary object of the present invention is to provide an electric brake system for an electric rolling stock which is rid of the foregoing prior art deficiencies.

The present invention provides an electrical brake system for an electric rolling stock comprising: a. a control means which performs regenerative control and generation control for a driving motor of said electric rolling stock so as to control electrical braking; b. a filter condenser connected together with said control means in parallel to a DC power supply; and c. a series circuit made up of a resistor and a resistor-chopper, and connected in parallel to said filter condenser, said control means reducing the regenerative current of said motor in response to the difference of a terminal voltage of said filter condenser from a first predetermined value when the terminal voltage of said filter condenser has risen higher than said first predetermined value, said control means reducing the regenerative current down to a value at which said regenerative control can barely be maintained when the terminal voltage of said filter condenser has reached a second predetermined value which is larger than said first predetermined value, said resistor chopper being operated when the terminal voltage of said filter condenser becomes equal to or larger than a third predetermined value which is larger than said second predetermined value so that a current in substantially equal magnitude to that of a regenerative current at a time of detecting said third predetermined voltage level is conducted to said series circuit and thereafter said resistorchopper reducing the series circuit current down to a predetermined value. Thus the invention achieves a control system which detects immediately a rising voltage across the filter condenser entering into the excessive range caused by an abrupt variation of the regenerative load on the trolly or a momentary separation of the pantagraph from the trolly, and operates a resistor chopper connected in parallel to the filter condenser so as to suppress the excessive voltage.

The invention further achieves a control system which reduces the current in the resistor chopper automatically in accordance with a predetermined timing pattern, and retains the regenerative control so the the regenerative braking current is not cut off completely, thereby allowing a quick rise of the regenerative current after the regenerative load on the trolly is restored or the pantagraph goes back to the trolly.

Embodiments of electrical brake system, in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a systematic diagram showing one embodiment of electrical brake system; Figure 2 is a block diagram explaining the control circuit shown in Fig. 1; Figure 3 is a block diagram explaining a modified control circuit; and Figure 4 is a systematic diagram showing another embodiment of brake system.

In Figures 1 and 2, reference number 1 denotes a trolly connected to a DC power source, 2 is a pantagraph, 3 is a filter reactor, 4 is a filter condenser, and 5 is a series circuit of a resistor 6 and resistor-chopper 7 connected in parallel to the filter condenser 4. Reference number 8 is a regenerative chopper made up of a chopping section 9, a blocking diode 10 and a smoothing reactor 11. Reference number 12 is a DC motor having an excitation winding 1 3 and an armature 14. Reference number 1 5 is a DC potential transformer (DCPT), 1 6 is a serial resistor, 1 7 is a DC current transformer (DCCT1) for sensing the current in the DC motor 12, and 18 is a DC current transformer (DCCT2) for sensing the current in the series circuit 5.Reference number 1 9 is a main motor current pattern (Ip) generator, and 20 is a regenerative current limiter which operates on the regenerative chopper 8 to reduce the motor current when the detected voltage Vc across the filter condenser 4 exceeds the first preset voltage level V,, and provides the maximum limiter output to minimize the motor current when the detected voltage Vc has reached the second preset voltage level V2 (V2 > V, ) thereby to suppress the regenerative current indirectly. The regenerative current limiter 20 is designed to have a control stability and proper response constant so that the electrical braking force and mechanical braking force are switched smoothly.

Reference number 21 is a filter condenser voltage comparator which issues a start command to operate the resistor-chopper 5 immediately when the voltage Vc has reached a predetermined level V3(V3 > V2). The voltage comparator 21 is designed to have proper hysteresis characteristics and timer characteristics so that it is deactivated when the voltage Vc goes down below V0(V0 < V1) or a predetermined To has elapsed.

Reference number 22 is a current detector for measuring the regenerative current 1, and, in this embodiment, the detector performs the arithmetic operation lL=lMX(lY) based on the current conducting duty cycle y of the regenerative chopper 8 and the detected motor current I As an alternative arrangement, the current i, flowing in the filter reactor 3 may be detected using a DC current transformer (not shown) instead of using the regenerative current detector 22.

Reference number 23 is a current pattern generator for creating a pattern IRP of the current BR conducted through the resistor-chopper 7. The current pattern generator 23 provides a current pattern Rp so that current BR is substantially equal to current 1, at the initial state when the voltage comparator 21 has issued a command to the resistor-chopper 5, and upon expiration of time T,, the circuit 23 reduces the IRP smoothly so that the i R becomes substantially zero.The resistorchopper 5 receives the detected value 1R of i A from the DC current transformer (DCCT2) 18 so as to perform the current control in accordance with the current pattern 1Ap In such an arrangement, if an abrupt variation of the trolly load or the like has occurred, the regenerative current i, is transferred immediately to the current 1R through the resistor chopper 7 so as to prevent the electrical braking force from varying sharply. When the filter condenser voltage Vc rises gradualiy due to the reduction of the resistor chopper current jR based on the timer pattern IRPT on the other hand the regenerative current limiter 20 operates to reduce the motor current smoothly.If the resistor chopper current finally becomes minimial or is cut off completely, the current control is performed for a small trolly load condition or no-load condition, where the power system is loaded only with auxiliary devices within the vehicle, solely by the regenerative chopper 8 including the current limiter 20. In consequence, when the trolly load is restored and the power voltage falls, causing the Vc to go back below V, the current limiter 20 is deactivated so the regenerative chopper 8 increases the motor current automatically and promptly up to Ip, and the normal regenerative control is restored.

The arrangement of the control circuit shown in Fig. 3 is basically identical to that of Fig. 2, and performs a slightly simplified control for the resistor-chopper 7. Specifically, the feedback of 1R is eliminated and the resistor chopper current is controlled on an open loop basis following the current conduction duty cycle pattern YAP provided by the current pattern generator 23. In this case, the value y, of the timer pattern YAP at starting is set automatically basing on the arithmetic operation YL=RN2XlL (where R is the resistance of the resistor 6, V2 is the second preset voltage level and 1, is the regenerative current value), and it becomes zero or minimal upon expiration of the time T,.

Figure 4 shows another ernbodiment of the present invention wherein the control unit employs a variable voltage variable frequency (VWF) inverter 24 so that the same effect of control is achieved for an induction motor 25 which serves as the driving motor for the electric rolling stock, whereas in the previous embodiment the regenerative chopper is used as the control unit.

Furthermore, the control unit may be of the conventional cam-contacts system.

According to the present invention, as described above, the voltage across the filter condenser is measured and compared with several preset values, and the control mode for the regenerative current is determined depending on the threshold exceeded by the filter condenser voltage. Accordingly, even after an abrupt variation in the trolly load or a coming off of the pantagraph from the trolly has occurred, the braking force is controlled stably while suppressing an excessive voltage across the filter condenser, and the regenerative braking is restored promptly.

Claims

1. An electrical brake system for an electric rolling stock comprising: a. a control means which performs regenerative control and generation control for a driving motor of said electric rolling stock so as to control electrical braking; b. a filter condenser connected together with said control means in parallel to a DC power supply; and c. a series circuit made up of a resistor and a resistor-chopper, and connected in parallel to said filter condenser, said control means reducing the regenerative current of said motor in response to the difference of a terminal voltage of said filter condenser from a first predetermined value when the terminal voltage of said filter condenser has risen higher than said first predetermined value, said control means reducing the regenerative current down to a value at which said regenerative control can barely be maintained when the terminal voltage of said filter condenser has reached a second predetermined value which is larger than said first predetermined values, said resistor chopper being operated when the terminal voltage of said filter condenser becomes equal to or larger than a third predetermined value which is larger than said second predetermined value so that a current in substantially equal magnitude to that of a regenerative current at a time of detecting said third predetermined voltage level is conducted to said series circuit and thereafter said resistorchopper reducing the series circuit current down to a predetermined value.

2. An electrical brake system according to claim 1, wherein said resistor-chopper is adapted to reduce the current in said series circuit in a time constant substantially equal to a response time constant of said control means in reducing the motor current, when the terminal voltage of said filter condenser has become equal to or higher than said third predetermined value.

3. An electrical brake system according to claim 1 or claim 2 wherein said series circuit comprises a resistor and a resistor-chopper connected in series to said resistor.

4. An electrical brake system according to claim 1, 2 or 3 wherein said control means comprises a regenerative chopper.

5. An electrical system according to claim 4, wherein said regenerative chopper comprises a chopping section, a blocking diode and a smoothing reactor.

6. an electrical brake system according to claim 1, 2 or 3 wherein said control means comprises a VWF inverter, and said driving motor is an induction motor.

7. An electrical brake system substantially as described herein with reference to or as illustrated in Figures 1 and 2, or Figure 3 or Figure 4 of the accompanying drawings.