JPS6333387B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric brake that stops a generator without opening a field or a disconnector. As is well known, electric braking is a method in which the generator circuit is short-circuited, a short-circuit current of about the rated current is applied, and the generator is braked by the generator's joule loss. With the recent high speeds and large capacities, the rotational energy of the rotating parts is large, and mechanical brakes are therefore subject to thermal constraints, which not only prolongs the stopping time but also increases wear on the brake shoes. Maintenance is also difficult. Therefore, the concept of using electric brakes to normally stop generators and using mechanical brakes only in emergencies has been gaining attention.

An example of a conventional electric brake will be explained with reference to FIG. 1 is a generator, 2 is a disconnector for electric brakes,
3 is the line disconnector, 4 is the main transformer, 5 is the potential transformer (PT), 6 is the excitation transformer, 7 is the automatic voltage regulator (AVR), 8 is the ignition circuit (GPG), 9 is a thyristor bridge, 10 is a field switch, 11 is a field discharge resistor, 12 is an excitation switch for initial excitation and electric braking, 13 is a thyristor bridge for it, 20 is a field It is a magnetic winding. In response to the generator stop command, the field disconnector 3 and field disconnector 10 are opened, the field current of the generator 1 is demagnetized, and when the generator voltage becomes only the residual voltage, the electric brake disconnector 2 is opened. Close the circuit. Next, an electric brake is applied by applying excitation to the field of the generator 1 through which a short-circuit current approximately equal to the rated current of the generator flows. The current during electric braking is given by the following equation.

Here, I: Current during electric braking S: Slip V: Generator voltage R: Armature resistance Field magnet and disconnector 1
This has the disadvantage that it not only shortens the life of the 0 but also complicates the control sequence. The present invention attempts to eliminate the above-mentioned drawbacks of the prior art by operating the electric brake without opening the field or the disconnector when the vehicle is stopped.

The configuration of an embodiment of the present invention will be explained with reference to FIG. The same reference numerals as in FIG. 1 indicate the same or equivalent products. 14 is a speed generator directly connected to the generator 1;
Reference numeral 15 is a speed relay connected to the speed generator 14, and the number of revolutions at which the electric brake is applied (generally about 50
%), and 16 is a low voltage detection relay that detects when the field energy is demagnetized by inverter operation of the thyristor bridge 9 and the voltage of the generator 1 has become sufficiently low (residual voltage). , 17 is a switching circuit for AVR operation, inverter operation, and electric braking, 18 is a firing angle control circuit for operating the thyristor bridge 9 as an inverter and inverting field energy through the transformer 6, and 19 is for electric braking. The firing angle control circuit 20 is a field winding.

Next, the operation will be explained. The breaker 3 is opened by the stop command. When the switching circuit 17 is switched to the firing angle control circuit 18 side, the field current is attenuated by the inverter operation of the thyristor bridge 9, and the generator 1
When the voltage drops to the residual voltage, the voltage relay 16
operates, and when the speed decreases due to natural deceleration and the speed relay 15 operates, the disconnector 2 is closed. The switching circuit 17 applies excitation suitable for the switching electric brake to the ignition angle control circuit 19 side, and causes the electric brake to stop. At this time, since the speed relay 15 and the low voltage detection relay 16 are provided, the most suitable timing for closing the disconnector 2 can be selected.

As described above, according to the present invention, it is possible to apply an electric brake without opening the field or disconnector, thereby extending the life of the field or disconnector. Since the brake can be applied at the optimal timing, stable dynamic braking can be performed.

[Brief explanation of the drawing]

FIG. 1 is a single-line connection diagram showing an example of a conventional electric brake, and FIG. 2 is a single-line connection diagram showing an embodiment of the electric brake according to the present invention. In the figure, 1 is a generator, 2 is a disconnector, 9 is a converter, 10 is a field disconnector, 14 is a speed generator,
15 is a speed relay, 16 is a low voltage detection relay, 1
8 is a first ignition signal control circuit, 19 is a second ignition signal generation circuit, and 20 is a field winding. The same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A converter connected to an AC power source and operating as a forward converter or an inverse converter according to an ignition control signal;
A field winding of the generator to which the forward output current of the converter is supplied, a disconnector that disconnects the generator from the grid in response to a stop command for the generator, and a disconnector that disconnects the generator from the grid when the generator is under dynamic braking. a first ignition signal generation circuit that controls ignition as an inverse converter to reduce the field current; and a first ignition signal generation circuit that is connected to the generator via a speed generator, and is connected to the generator through a speed generator, and the generator speed is reduced to a predetermined speed or less. a speed relay that operates when the first ignition signal generation circuit reduces the field current and the voltage of the generator drops to a residual voltage, and a low voltage detection relay that operates when the first ignition signal generation circuit Under the condition that the voltage of the generator falls below a predetermined value by the signal generating circuit and the micro voltage detection relay and speed relay operate, the converter is operated as a forward converter to cause the field winding to reach a predetermined value. A dynamic braking device for a generator, comprising a second ignition signal generation circuit that controls ignition so that current flows, and a disconnector that short-circuits the output of the generator when the second ignition signal generation circuit is activated. .