SU528665A1 - Device for uninterrupted power supply - Google Patents

Description

one

The invention relates to the field of protection of the system of coordinated rotation of electric drives.

At present, devices are being used to protect the electric shaft from falling out of machinery out of sync with the interruption in centralized power supply, which is designed as an emergency generator with a flywheel on the shaft and used as auxiliary power sources.

Such devices have been used in heavy lathe-screw-cutting machines, where an electric shaft is installed instead of a spindle for connecting the main drive of the faceplate with the caliper feed drive. In case of a sudden interruption in the centralized power supply, the synchronous communication between the main drive and the feed drive of the caliper is disrupted, which may result in damage to expensive parts that are being processed. In this case, along with the emergency retraction of the cutter, in order to protect against possible rejects, an auxiliary source is used in the form of a generator with a flywheel, supported by the energy stored in the flywheels, coordinated rotation of the actuators until the machine stops.

Devices for uninterrupted power supply of electric shaft machines are known, where a synchronous generator serves as an auxiliary emergency power source. In the period of normal operation of the installation (machine), the synchronous generator rotates with the help of a drive induction motor, is energized and operates in parallel with the common network. In the event of an interruption in the centralized power supply, the machines of the electric shaft, up to their full coordinated shutdown, are powered by the energy stored in the generator flyweight. Protection devices with a synchronous generator are not widely used due to their bulkiness and high cost due to the need for an additional drive induction motor and driver.

Unlike a device with a synchronous generator, the proposed protection device

Does not need an additional drive motor.

Closest to the present, there is a protection device with an asynchronous self-exciting generator. The asynchronous generator also does not require an additional drive motor. An asynchronous machine that performs the functions of an asyn chronal generator is floated as a conventional asynchronous motor. AT

period of normal operation of the machine

asynchronous machine works in the engine mode, rotating the flywheel. In the event of an interruption in the centralized power supply, the asynchronous machine is excited by the reactive current of the capacitor bank, does not return to the generator mode, and becomes an emergency source of electrical power for the electric shaft system.

However, the sharp dependence of the voltage of the asynchronous self-exciting generator on the rotational speed should be noted. As the flywheel speed decreases, the voltage across the generator terminals quickly drops. Compensating for voltage reduction by increasing the initial capacitance of a capacitor battery leads to an unacceptable increase in braking torque on the generator shaft. Moreover, the braking torque may be several times higher than the nominal value even when the generator is idling.

Thus, the shortcomings of the protection device with a self-excited asynchronous generator should include a large braking torque arising on the shaft during capacitor excitation, overestimated dimensions of the flywheel, as well as a large capacitance of the capacitor battery.

In order to facilitate the start-up and excitation of the asynchronous generator by introducing additional excitation from the rotor circuits, in the proposed device, between the two rotor phases closed short and the third phase, the capacitance is bridged by a circuit from the throttle and valve bridge, which is connected to the main power source through a matching transformer and the stator winding of the asynchronous generator.

Switching on the capacitance between the two rotor phases of the rotor and the third phase, as well as shunting this section with a chain from the valve bridge, allows increasing the active component of the rotor current and thereby easing the conditions for starting an asynchronous machine operating in the simultaneous excitation mode. The use of the simultaneous excitation of an asynchronous generator by the reactive current of a capacitor battery connected to the stator winding and by a direct current from the side of the rotor circuit facilitates self-excitation conditions and reduces the dependence of the voltage at the terminals of the generator on the speed of rotation. The consequence of this is a smaller capacitance of the excitation capacitors, a smaller braking torque and smaller flywheel dimensions.

The drawing shows a diagram of the proposed device.

A capacitor bank 4 is connected to the stator winding of the asynchronous generator 1 connected to machines 2 and 3 of the electric shaft. The capacity of the battery is chosen enough to initiate a self-excitation process. On the generator shaft is located flywheel GH

The excitation voltage from the rectifier containing matching transformer 6 and valve bridge 7 is applied to the rotor winding, the two phases of which are short-circuited. The inclusion of the valve bridge, droplets 8 and capacitance 9, which additionally plays the additional role of a smoothing filter, in the rotor circuit facilitates the starting conditions and driving an asynchronous generator.

The induction of the asynchronous generator 1 is performed simultaneously with connecting the machines 2 and 3 of the electric shaft to the main power source by closing the switch 10.

The switch performs another auxiliary function — it turns off the circuit section containing the asynchronous generator 1

and electric shaft machines from the common shop network when the centralized power supply is interrupted so that the energy stored in the fly masses is not spent on other consumers connected to the common shop network and used for its intended purpose: to maintain synchronous overrun of the electric shaft machines. In the installation, the function of the switch 10 is performed by the magnetic starter on the contactor. In the interruption of

The centralized power supply is given a pulse to turn off the switch 10. The pulse is supplied using any device that reacts to a change in the direction of power flow, for example using

commercially available power direction relays.

The device works as follows. To start the asynchronous generator 1, the switch 10 is turned on. In this case, an asynchronous start is carried out, during which the machine accelerates to a speed close to synchronous, then it is automatically drawn into synchronization. During the normal operation of the machine, the asynchronous maschine 1 works in the motor mode, spinning the flywheel 5 and the reserve of mechanical energy in case of interruption in the power supply.

When the centralized power supply is interrupted, the asynchronous generator 1, self-excited by the reactive current of the capacitors 4 on the side of the stator circuit and direct current on the side of the rotor circuit, becomes an auxiliary power source for the electric shaft 2 and 3

to a complete stop of the electric drives of the machine.

At the same time, an impulse is applied at the disconnection of the switch 10.

Simultaneous excitation of asynchronous

a generator with reactive current from the side of the stator circuit and a direct current from the side of the rotor circuit allows to ease the starting and excitation conditions of the asynchronous machine to go into the generator mode. Additional excitement from the rotor

the circuit reduces the dependence of the generator voltage on the speed vran1, en11. S. psdstini this nmenmen1,1na required for the excitation of the capacitor capacitance of the battery, meyshi braking torque, the smaller size of the flywheel. According to the calculation and experimental verification of the operation of the proposed device while simultaneously driving an asynchronous generator, the capacitance of the excitation capacitors decreases 3 times. Flywheel dimensions are reduced by 30%.

Claims (2)

1. A device for uninterrupted power supply, containing its main source of three-phase power supply, a switch and Additional power source - asynh | joiiHbiA generator with flywheel and capacitor 1 o: boules) 1 from the side of the stator winding, characterized in that, in order to alleviate the conditions of the start and excite the asynchronous generator by introducing additional excitation of the rotor price between the two rotor phases, short-circuited, and the third phase, a capacitance is connected, shunted with a value from the throttles and the valve bridge, which is connected to the main power source and the stator winding ac through a matching transformer nhronnogo generator. 2. Device but n. 1, characterized in that, instead of a valve bridge, the battery is switched on.