RU2305354C2 - Method for protecting self-excited generator - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: proposed method that can be used in off-line power supply systems feeding railway cars equipped with self-excited generators for regulating generator field current includes generator disconnection, selection of pulses arriving from pulse-width modulator with respect to their length, as well as de-energizing of field coil and de-excitation of generator in case pulse length is not kept within desired range. To this end single clocking failures are corrected and generator serviceability is recovered.

EFFECT: reduced transients, enlarged service life of switching devices, enhanced operating reliability, reduced mass, size, and cost, unambiguous trouble location.

1 cl, 1 dwg

Description

The method of protection of self-excitation electric generator relates to electrical engineering and can be used in autonomous power supply systems of railway cars with self-excitation electric generators for regulating the excitation current of electric generators.

The known method, taken as a prototype (see. Regulation and control device of an autonomous energy supply system DUGG28B. Technical description 2470.072-973: 61/9, page 2, 9. Functional diagram 2470.072-974: 61/9, page 1, Berlin , 1993 YG) protects the generator self-excitation in case of failures or absence of a timing drive voltage so that the voltage at the excitation winding (U _s) is integrated and the integrated value exceeding the allowable (∫U _RH> U _ext) shorted output of the power generator, while short-circuit current include linear circuit breaker (FFA), which disconnects the power generator.

The disadvantages of this method of protecting the self-excitation generator:

- significant transient processes when switching short-circuit currents of an electric generator, which worsens the noise situation for electronic equipment;

- reducing the resource of switching elements and, therefore, operational reliability;

- a limited range of operation according to the input voltage of the generator U _g (only when U _s > U _ext );

- in case of single failures from the effects of interference, the LAZ disconnects the generator and for the resumption of work functions requires the intervention of maintenance personnel, which complicates the operation;

- after shutting down the LAZ, it is impossible to unambiguously determine the cause, which increases the time for troubleshooting;

- significant weight and size characteristics and high cost during implementation;

- increased probability of centrifugal clutch failure from overload when working with T _and > T _{and max} , especially at the time of switching on, since in this case there will be a more intense increase in excitation of the electric generator at a low axis rotation speed when the clutch is not yet turned on.

The task is to reduce transients during operation of the device, increase the resource of switching elements and reliability, counter single failures, localize the place of failure, lower the cost of protection of the electric generator, expand the range of operation in relation to the voltage of the electric generator, and reduce the likelihood of centrifugal clutch failure from overload.

The problem is solved in that in the method of protecting the self-excitation electric generator, which consists in disconnecting the electric generator in accordance with the utility model, the pulse duration is selected from the pulse-width modulator, and if the pulse duration is not in the specified range, the excitation winding is de-energized and excite the electric generator.

The essence of the proposed method is illustrated by a protection device, a block diagram of which is shown in the drawing.

The protection device contains a linear circuit breaker (LAZ) 1 with a remotely controlled release, a power switch 2, a control device 3 with a power switch, a power unit 4, a selector 5, an excitation winding 6 of the generator, a bistable device 7, a device 8 time delay signal, latitudinal pulse modulator (PWM) 9, generator 10.

The protection device operates as follows.

The voltage from the self-excitation generator (U _g ) through a linear circuit breaker (LAZ) 1 is supplied to the input of the power switch 2, the output of which is connected to the excitation winding 6.

Clock pulses of variable duration T _and from 0 to T _{and max} from the PWM output 9 are fed to the input of the control device 3 and switch the power switch 2, as a result of which excitation voltage pulses with a level of approximately U _g appear on the field winding, the duration of which repeats the duration of the clock pulses from PWM.

By changing the pulse duration of the excitation voltage T _and = 0 ... T _{and max} , the output parameters of the generator are regulated.

Adjustable values, such as: unit voltage (U _y ), battery current (I _B ), generator current (I _g ), excitation current are measured by measuring links, compared with set values and processed by appropriate control amplifiers. The output voltages of these control amplifiers are supplied to a pulse-width modulator. The output voltage of that amplifier, the measurement value of which exceeds the set value as much as possible, is compared here with a sawtooth voltage with a frequency of about 1 kHz and converted into a rectangular signal, the duration of which corresponds to the voltage of the control amplifier. This square-wave signal controls the above power switch. Thus, when the generator is operating through a clocked excitation voltage, an average excitation current is provided that supports adjustable parameter values.

When approaching, for example, I _g , to the maximum allowable value, the pulse width from the PWM output decreases, and the pulse voltage of the excitation voltage decreases to almost 0, the generator is de-energized, the generator current decreases, the difference between I _{g max} and I _{g current} and pulse duration increases from the output, the PWM starts to increase, perhaps to T _{and max} .

At the same time, pulses from the PWM are fed to the input of a selector of duration 5. As soon as T _and > T _{and max} , for example, when exposed to powerful interference, the signal from the output of the selector of duration 5 through the control device 3 and the power switch 2 blocks the current connection of the generator with the excitation winding 6. After the interference disappears and the PWM pulse duration returns to normal, the blocking signal is removed and the excitation voltage clocking resumes.

Thus, when a single powerful interference occurs on the clock path from the PWM, after removing the interference, the device’s operability is automatically restored. In the event of a PWM failure or a fault in the communication line with the PWM, the power switch 2 remains locked.

Only with a short circuit of the power switch 2, a constant voltage (+ U _r ) will be present on the field winding, from which the bistable device 7 is activated and its output signal through the time delay device 8 is fed to a remotely controlled LAZ 1 release and turns off the generator 10.

Thus, the proposed method allows you to:

- reduce transients, because the work is done by control currents, which are significantly less than the short circuit currents of the prototype;

- increase the resource of switching elements and increase operational reliability;

- fend off single clock failures and automatically restore performance;

- to provide low weight and size characteristics and low cost during implementation;

- unambiguously localize the place of the malfunction and thereby increase the coefficient of availability of cars by reducing the time to search for malfunctions and restore working functions, namely:

a) the power switch is blocked - failure of the control path from the PWM;

b) LAZ 1 is off - a short circuit in the power switch in the power unit;

- reduce the likelihood of a centrifugal clutch failure in the event of a failure or lack of clocking of the excitation voltage, since the pulse duration selector blocks the power switch at T _and > T _{and max,} and thereby eliminates the possibility of an abnormal increase in the excitation of the generator;

- expand the range of operation with respect to the output voltage of the generator U _g , since the generator can be turned off even when the voltage on the field winding is slightly larger than the initial one, due to the residual magnetization of the magnetic core of the generator (≈10 V).

Claims (1)

A method of protecting the self-excitation electric generator in case of failures or the absence of clocking of the excitation voltage, which consists in turning off the electric generator, characterized in that the pulse duration is selected from the pulse-width modulator, and if the pulse duration is not in a predetermined range, the excitation winding is de-energized and excite the electric generator.