SU1403201A2 - Arrangement for protecting synchronous electric drive from asynchronous mode - Google Patents

Abstract

This invention relates to electrical engineering, in particular, to relay protection. The purpose of the invention is the expansion of functional capabilities by detecting a surge mode. The device contains a voltage converter 1 and a current converter 2, the inputs of which are supplied with voltage and the stator current of the protected motor, and the outputs of which are connected to the inputs of the comparison unit 4, the auxiliary current transformer 3, the primary winding of which is connected to the secondary winding of the voltage converter 1, and the secondary - to the secondary winding of the current converter 2, the first block of the time delay 5, the input of which is connected to the output of the comparison unit 4, and the output - to the first input of the expander pulse 6, the output of the pulse expander 6 is connected to the input of the execution unit 8, and the second time delay unit 7, whose input is connected to the output of the comparison unit 4, and the output to the second input of the pulse expander 6. The introduction of the second time delay unit allows comparing the time charge capacitor 17 until the voltage of the breakdown of Zener diode 22 and the opening of transistor 11 with a positive pulse duration inversely proportional to the load angle, fix the zone of normal operation of the centrifugal compressor. 3 il. (About ate

Description

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The invention relates to electrical engineering, namely to protection devices for synchronous motors.

The purpose of the invention is to expand the functionality of the device by detecting a surge mode.

FIG. 1 is a schematic diagram of the device with the allocation of functional blocks; in fig. 2 - angular shift between the current and the stator voltage of the motor; in fig. 3 - time pulse diagrams of operation of the main elements of the device.

The device contains a voltage converter 1 (ПН), a current converter 2 (ПТ), an auxiliary current transformer 3 (ВТТ), a comparison block (БС) 4, a first time delay unit 5 (БВЗ), a pulse extender 6 (РИ), the second block 7 time delay (BVZ), the Executive unit 8 (IV).

A voltage is applied to the input 11Н 1, and a current of the same phase of the engine being protected is fed to the input of the PT 2. In PN 1 and PT 2, positive half-wave voltage and current are extracted from sinusoidal input signals and input to BS 4. The latter compares input signals in time and generates an output signal that is inversely proportional to the phase shift of output signals PN i and PT 2. The output signal from the BS 4 is fed to the first 5 and second 7 BVZ, where its duration is compared with the set value of the time delay of the BVZ 5 and 7.

In addition, the device contains transistors 9-14, thyristor 15, capacitors 16-20, zener diodes 21-24, included in the base circuits of each transistor 10-13, and the executive body 25.

The device works as follows.

When the BS 4 output signal duration specified in time delay blocks is exceeded, the output signals of the BVZ 5 and 7 are output to the first and second inputs of the PSI 6. If there are signals on the first and second inputs of the PS 6, there is no output on the PS 6 simultaneously and the device doesn't work. When a signal arrives only at the first input of the RI 6 from the first BVZ 5 at the output of the RI 6 over V, 1 the output signal arriving at IB 8, which is triggered after a specified time delay and performs the contact output of the device.

Any phase voltage is applied to the input of the PN 1, and a current of the same phase is applied to the input of the ПТ 2. The phase shift between the input monitored values is equal to the load angle.

In the static state, transistors 9 and 10 are open, and transistors 11-14 and thyristor 15 are closed, capacitors 16, 17, 19, and 20 are discharged, and capacitor 18 is charged

before the voltage breakdown of the Zener diode 23. The executive relay 25 did not work.

With stable synchronous operation of the motor and no compressor surge mode, the angle φ (Fig. 2) between the controlled current and voltage is in zone A. The angle φ with the leading current has the sign "+", and with the lagging sign the sign "-. The boundary values of the angles of zone A ± phg depend on the magnitude of the excitation current and on the engine load. According to the principle of operation of the device, it is necessary that with stable synchronous operation of the electric motor and the absence of compressor surge mode at the output of the second BVZ 7, a signal appears that blocks the response of the RI 6 and IB 8. To do this, the time delay for the second BVZ 7 to operate the charging time of the co) of the sensor 17 to the voltage of the breakdown of the zener diode 22 was no more than the duration of the positive pulse (Beats at the output of BS 4, with angle values. The pulse duration Ug is inversely proportional to the absolute value of la and at a frequency f

ac current fc is equal to L (180-f) X

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in this case, when the capacitor 17 during the time of the existence of a positive

The Q pulse Ug (fig. Za) has time to charge before the voltage of the breakdown of the zener diode 22. When penetrating, the zener diode 22 opens the transistor I, which, in turn, bypassing the capacitor 19, prohibits the opening of the transistor 13 and the operation of IB 8.

5 If synchronism is lost, the motor goes into the mode of reactive power consumption and the angle φ in this case is in the angle zone B, and in the surge mode the engine outputs the reactive power to the network and the angle Φ is in zone C.

0 In these cases, the duration of the positive pulses is reduced, since | Φ2 | 1F ||, the capacitor 17 does not have time to charge before the voltage of the breakdown of the zener diode 22, the transistor 11 is closed and will not interfere with the capacitor 19. The time delay for the actuation of the second BHD 7 is assumed to be equal to the duration of the positive pulses UQ at the angle values and is determined by the charging time of the capacitor 16 until the breakdown voltage is stabilized. 21.

When the angle in the case of abnormal operation of the motor with a compressor in an asynchronous or surge mode, the capacitor 16 during the existence of a positive pulse has time to charge before the voltage of the breakdown of the Zener diode 21. Punching through, the Zener 21 opens the transistor 12, which, to the shunt capacitor 18, provides the closed state of the transistor 10, which also does not prevent the charging of the capacitor 19. As a result, the capacitor 19, charging up to the voltage of the breakdown of the zener diode 24, provides its breakdown and opening anzistor 13. Next, through the open transistor 13, the capacitor 20 begins to charge. The time it takes to charge the open voltage of the transistor 14 determines the time delay for the device to operate. After the transistor 14 is opened, the transistor 15 opens and the actuating relay 25 operates. The pickup zone of the device is controlled by variable resistors 26 and 27. The time delay is required to tune away from random disturbances and can be changed within the required limits by the adjustable resistor 28.

The introduction of a second time delay unit, by comparing the charging time of the capacitor 17 to the breakdown voltage of the Zener diode 22 and opening the transistor II with the positive pulse Ug, inversely proportional to the angle cp, fixes the zone of normal stable operation of the centrifugal compressor and drive motor.

In a similar way, using the first block of the time delay, the normal, asynchronous and surge modes are fixed simultaneously.

Claims (1)

Invention Formula Device to protect a synchronous drive from asynchronous mode by aut. St. LG 909745, characterized in that 5, in order to extend the functionality by detecting the surge mode, it is additionally equipped with a second time delay unit, the input of which is connected to the output of the comparison unit, and the output - to the second input of the expander PULSES. f / fJ t / s ( and, b ur, uis and. -one X-TN  p U, l ii.f / G 1.1 11 1 I I I I G